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Tizifa TA, Kabaghe AN, McCann RS, Gowelo S, Malenga T, Nkhata RM, Chapeta Y, Nkhono W, Kadama A, Takken W, Phiri KS, van Vugt M, van den Berg H, Manda-Taylor L. Assessing the implementation fidelity, feasibility, and sustainability of community-based house improvement for malaria control in southern Malawi: a mixed-methods study. BMC Public Health 2024; 24:951. [PMID: 38566043 PMCID: PMC10988826 DOI: 10.1186/s12889-024-18401-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Accepted: 03/20/2024] [Indexed: 04/04/2024] Open
Abstract
BACKGROUND Despite significant success in the fight against malaria over the past two decades, malaria control programmes rely on only two insecticidal methods: indoor residual spraying and insecticidal-treated nets. House improvement (HI) can complement these interventions by reducing human-mosquito contact, thereby reinforcing the gains in disease reduction. This study assessed the implementation fidelity, which is the assessment of how closely an intervention aligns with its intended design, feasibility, and sustainability of community-led HI in southern Malawi. METHODS The study, conducted in 22 villages (2730 households), employed a mixed-methods approach. Implementation fidelity was assessed using a modified framework, with longitudinal surveys collecting data on HI coverage indicators. Quantitative analysis, employing descriptive statistics, evaluated the adherence to HI implementation. Qualitative data came from in-depth interviews, key informant interviews, and focus groups involving project beneficiaries and implementers. Qualitative data were analysed using content analysis guided by the implementation fidelity model to explore facilitators, challenges, and factors affecting intervention feasibility. RESULTS The results show that HI was implemented as planned. There was good adherence to the intended community-led HI design; however, the adherence could have been higher but gradually declined over time. In terms of intervention implementation, 74% of houses had attempted to have eaves closed in 2016-17 and 2017-18, compared to 70% in 2018-19. In 2016-17, 42% of houses had all four sides of the eaves closed, compared to 33% in 2018-19. Approximately 72% of houses were screened with gauze wire in 2016-17, compared to 57% in 2018-19. High costs, supply shortages, labour demands, volunteers' poor living conditions and adverse weather were reported to hinder the ideal HI implementation. Overall, the community described community-led HI as feasible and could be sustained by addressing these socioeconomic and contextual challenges. CONCLUSION Our study found that although HI was initially implemented as planned, its fidelity declined over time. Using trained volunteers facilitated the fidelity and feasibility of implementing the intervention. A combination of rigorous community education, consistent training, information, education and communication, and intervention modifications may be necessary to address the challenges and enhance the intervention's fidelity, feasibility, and sustainability.
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Affiliation(s)
- Tinashe A Tizifa
- Center for Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Division of Internal Medicine, University of Amsterdam, Amsterdam University Medical Center, Location Academic Medical Center, Amsterdam, The Netherlands.
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi.
| | - Alinune N Kabaghe
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Robert S McCann
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
- Centre for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, USA
| | - Steven Gowelo
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Tumaini Malenga
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
- National TB and Leprosy Elimination Programme, Ministry of Health, Lilongwe, Malawi
| | - Richard M Nkhata
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Yankho Chapeta
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
- Biological Sciences Department, Mzuzu University, Mzuzu, Malawi
| | - William Nkhono
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Asante Kadama
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Kamija S Phiri
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Michele van Vugt
- Center for Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Division of Internal Medicine, University of Amsterdam, Amsterdam University Medical Center, Location Academic Medical Center, Amsterdam, The Netherlands
| | - Henk van den Berg
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Lucinda Manda-Taylor
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
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Fillinger U, Denz A, Njoroge MM, Tambwe MM, Takken W, van Loon JJA, Moore SJ, Saddler A, Chitnis N, Hiscox A. A randomized, double-blind placebo-control study assessing the protective efficacy of an odour-based 'push-pull' malaria vector control strategy in reducing human-vector contact. Sci Rep 2023; 13:11197. [PMID: 37433881 DOI: 10.1038/s41598-023-38463-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Accepted: 07/08/2023] [Indexed: 07/13/2023] Open
Abstract
Novel malaria vector control strategies targeting the odour-orientation of mosquitoes during host-seeking, such as 'attract-and-kill' or 'push-and-pull', have been suggested as complementary tools to indoor residual spraying and long-lasting insecticidal nets. These would be particularly beneficial if they can target vectors in the peri-domestic space where people are unprotected by traditional interventions. A randomized double-blind placebo-control study was implemented in western Kenya to evaluate: a 'push' intervention (spatial repellent) using transfluthrin-treated fabric strips positioned at open eave gaps of houses; a 'pull' intervention placing an odour-baited mosquito trap at a 5 m distance from a house; the combined 'push-pull' package; and the control where houses contained all elements but without active ingredients. Treatments were rotated through 12 houses in a randomized-block design. Outdoor biting was estimated using human landing catches, and indoor mosquito densities using light-traps. None of the interventions provided any protection from outdoor biting malaria vectors. The 'push' reduced indoor vector densities dominated by Anopheles funestus by around two thirds. The 'pull' device did not add any benefit. In the light of the high Anopheles arabiensis biting densities outdoors in the study location, the search for efficient outdoor protection and effective pull components needs to continue.
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Affiliation(s)
- Ulrike Fillinger
- International Centre of Insect Physiology and Ecology (Icipe), Human Health Theme, Nairobi, 00100, Kenya.
| | - Adrian Denz
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Kreuzstrasse 2, Allschwil, Switzerland
- University of Basel, Petersplatz 1, Basel, Switzerland
| | - Margaret M Njoroge
- International Centre of Insect Physiology and Ecology (Icipe), Human Health Theme, Nairobi, 00100, Kenya
- Laboratory of Entomology, Wageningen University & Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
| | - Mohamed M Tambwe
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Kreuzstrasse 2, Allschwil, Switzerland
- University of Basel, Petersplatz 1, Basel, Switzerland
- Vector Control Product Testing Unit (VCPTU), Department of Environmental Health and Ecological Sciences, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania
| | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
| | - Joop J A van Loon
- Laboratory of Entomology, Wageningen University & Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
| | - Sarah J Moore
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Kreuzstrasse 2, Allschwil, Switzerland
- University of Basel, Petersplatz 1, Basel, Switzerland
- Vector Control Product Testing Unit (VCPTU), Department of Environmental Health and Ecological Sciences, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania
- The Nelson Mandela African Institution of Science and Technology (NM-AIST), Tengeru, P.O. Box 447, Arusha, Tanzania
| | - Adam Saddler
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Kreuzstrasse 2, Allschwil, Switzerland
- University of Basel, Petersplatz 1, Basel, Switzerland
- Vector Control Product Testing Unit (VCPTU), Department of Environmental Health and Ecological Sciences, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania
- Telethon Kids Institute, Perth, Australia
| | - Nakul Chitnis
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Kreuzstrasse 2, Allschwil, Switzerland
- University of Basel, Petersplatz 1, Basel, Switzerland
| | - Alexandra Hiscox
- Laboratory of Entomology, Wageningen University & Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
- Arctech Innovation Ltd., The Cube, Londoneast-Uk Business and Technical Park, Yew Tree Avenue, Dagenham, RM10 7FN, UK
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Gowelo S, Meijer P, Tizifa T, Malenga T, Mburu MM, Kabaghe AN, Terlouw DJ, van Vugt M, Phiri KS, Mzilahowa T, Koenraadt CJM, van den Berg H, Manda-Taylor L, McCann RS, Takken W. Community Participation in Habitat Management and Larviciding for the Control of Malaria Vectors in Southern Malawi. Am J Trop Med Hyg 2023; 108:51-60. [PMID: 36410320 PMCID: PMC9833073 DOI: 10.4269/ajtmh.21-1127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Accepted: 08/23/2022] [Indexed: 11/23/2022] Open
Abstract
Larval source management (LSM) could reduce malaria transmission when executed alongside core vector control strategies. Involving communities in LSM could increase intervention coverage, reduce operational costs, and promote sustainability via community buy-in. We assessed the effectiveness of community-led LSM to reduce anopheline larval densities in 26 villages along the perimeter of Majete Wildlife Reserve in southern Malawi. The communities formed LSM committees which coordinated LSM activities in their villages following specialized training. Effectiveness of larviciding by LSM committees was assessed via pre- and post-spray larval sampling. The effect of community-led LSM on anopheline larval densities in intervention villages was assessed via comparisons with densities in non-LSM villages over a period of 14 months. Surveys involving 502 respondents were undertaken in intervention villages to explore community motivation and participation, and factors influencing these outcomes. Larviciding by LSM committees reduced anopheline larval densities in post-spray sampling compared with pre-spray sampling (P < 0.0001). No differences were observed between anopheline larval densities during pre-spray sampling in LSM villages and those in non-LSM villages (P = 0.282). Knowledge about vector biology and control, and someone's role in LSM motivated community participation in the vector control program. Despite reducing anopheline larval densities in LSM villages, the impact of the community-led LSM could not be detected in our study setting because of low mosquito densities after scale-up of core malaria control interventions. Still, the contributions of the intervention in increasing a community's knowledge of malaria, its risk factors, and its control methods highlight potential benefits of the approach.
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Affiliation(s)
- Steven Gowelo
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi.,Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands.,MAC Communicable Diseases Action Centre, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Paola Meijer
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Tinashe Tizifa
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi.,Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - Tumaini Malenga
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi.,African Institute for Development Policy, Lilongwe, Malawi
| | - Monicah M Mburu
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi.,Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands.,Macha Research Trust, Choma, Zambia
| | - Alinune N Kabaghe
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi.,Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - Dianne J Terlouw
- Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Michèle van Vugt
- Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - Kamija S Phiri
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Themba Mzilahowa
- MAC Communicable Diseases Action Centre, Kamuzu University of Health Sciences, Blantyre, Malawi
| | | | - Henk van den Berg
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Lucinda Manda-Taylor
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Robert S McCann
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi.,Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands.,Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, Maryland
| | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
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Krawczyk AI, Röttjers S, Coimbra-Dores MJ, Heylen D, Fonville M, Takken W, Faust K, Sprong H. Tick microbial associations at the crossroad of horizontal and vertical transmission pathways. Parasit Vectors 2022; 15:380. [PMID: 36271430 PMCID: PMC9585727 DOI: 10.1186/s13071-022-05519-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Accepted: 09/29/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Microbial communities can affect disease risk by interfering with the transmission or maintenance of pathogens in blood-feeding arthropods. Here, we investigated whether bacterial communities vary between Ixodes ricinus nymphs which were or were not infected with horizontally transmitted human pathogens. METHODS Ticks from eight forest sites were tested for the presence of Borrelia burgdorferi sensu lato, Babesia spp., Anaplasma phagocytophilum, and Neoehrlichia mikurensis by quantitative polymerase chain reaction (qPCR), and their microbiomes were determined by 16S rRNA amplicon sequencing. Tick bacterial communities clustered poorly by pathogen infection status but better by geography. As a second approach, we analysed variation in tick microorganism community structure (in terms of species co-infection) across space using hierarchical modelling of species communities. For that, we analysed almost 14,000 nymphs, which were tested for the presence of horizontally transmitted pathogens B. burgdorferi s.l., A. phagocytophilum, and N. mikurensis, and the vertically transmitted tick symbionts Rickettsia helvetica, Rickettsiella spp., Spiroplasma ixodetis, and Candidatus Midichloria mitochondrii. RESULTS With the exception of Rickettsiella spp., all microorganisms had either significant negative (R. helvetica and A. phagocytophilum) or positive (S. ixodetis, N. mikurensis, and B. burgdorferi s.l.) associations with M. mitochondrii. Two tick symbionts, R. helvetica and S. ixodetis, were negatively associated with each other. As expected, both B. burgdorferi s.l. and N. mikurensis had a significant positive association with each other and a negative association with A. phagocytophilum. Although these few specific associations do not appear to have a large effect on the entire microbiome composition, they can still be relevant for tick-borne pathogen dynamics. CONCLUSIONS Based on our results, we propose that M. mitochondrii alters the propensity of ticks to acquire or maintain horizontally acquired pathogens. The underlying mechanisms for some of these remarkable interactions are discussed herein and merit further investigation. Positive and negative associations between and within horizontally and vertically transmitted symbionts.
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Affiliation(s)
- Aleksandra Iwona Krawczyk
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Antonie van Leeuwenhoeklaan 9, 3720 MA, Bilthoven, The Netherlands. .,Laboratory of Entomology, Wageningen University & Research, 6708PB, Wageningen, The Netherlands.
| | - Sam Röttjers
- Department of Microbiology, Immunology and Transplantation, Laboratory of Molecular Bacteriology, KU Leuven, Rega Institute for Medical Research, 3000, Leuven, Belgium
| | - Maria João Coimbra-Dores
- Centre for Environmental and Marine Studies (CESAM), Departamento de Biologia Animal, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
| | - Dieter Heylen
- Interuniversity Institute for Biostatistics and Statistical Bioinformatics, Hasselt University, Diepenbeek, Belgium.,Department of Ecology and Evolutionary Biology, Princeton University, 106A Guyot Ln, Princeton, NJ, 08544, USA
| | - Manoj Fonville
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Antonie van Leeuwenhoeklaan 9, 3720 MA, Bilthoven, The Netherlands
| | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, 6708PB, Wageningen, The Netherlands
| | - Karoline Faust
- Department of Microbiology, Immunology and Transplantation, Laboratory of Molecular Bacteriology, KU Leuven, Rega Institute for Medical Research, 3000, Leuven, Belgium
| | - Hein Sprong
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Antonie van Leeuwenhoeklaan 9, 3720 MA, Bilthoven, The Netherlands.
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5
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Krawczyk AI, Röttjers L, Fonville M, Takumi K, Takken W, Faust K, Sprong H. Quantitative microbial population study reveals geographical differences in bacterial symbionts of Ixodes ricinus. Microbiome 2022; 10:120. [PMID: 35927748 PMCID: PMC9351266 DOI: 10.1186/s40168-022-01276-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 04/20/2022] [Indexed: 05/29/2023]
Abstract
BACKGROUND Ixodes ricinus ticks vector pathogens that cause serious health concerns. Like in other arthropods, the microbiome may affect the tick's biology, with consequences for pathogen transmission. Here, we explored the bacterial communities of I. ricinus across its developmental stages and six geographic locations by the 16S rRNA amplicon sequencing, combined with quantification of the bacterial load. RESULTS A wide range of bacterial loads was found. Accurate quantification of low microbial biomass samples permitted comparisons to high biomass samples, despite the presence of contaminating DNA. The bacterial communities of ticks were associated with geographical location rather than life stage, and differences in Rickettsia abundance determined this association. Subsequently, we explored the geographical distribution of four vertically transmitted symbionts identified in the microbiome analysis. For that, we screened 16,555 nymphs from 19 forest sites for R. helvetica, Rickettsiella spp., Midichloria mitochondrii, and Spiroplasma ixodetis. Also, the infection rates and distributions of these symbionts were compared to the horizontally transmitted pathogens Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum, and Neoehrlichia mikurensis. The infection rates of all vertically transmitted symbionts differed between the study sites, and none of the symbionts was present in all tested ticks suggesting a facultative association with I. ricinus. The proportions in which symbionts occurred in populations of I. ricinus were highly variable, but geographically close study sites expressed similar proportions. These patterns were in contrast to what we observed for horizontally transmitted pathogens. Lastly, nearly 12% of tested nymphs were free of any targeted microorganisms, which is in line with the microbiome analyses. CONCLUSIONS Our results show that the microbiome of I. ricinus is highly variable, but changes gradually and ticks originating from geographically close forest sites express similar bacterial communities. This suggests that geography-related factors affect the infection rates of vertically transmitted symbionts in I. ricinus. Since some symbionts, such as R. helvetica can cause disease in humans, we propose that public health investigations consider geographical differences in its infection rates.
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Affiliation(s)
- Aleksandra I Krawczyk
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Antonie van Leeuwenhoeklaan 9, Bilthoven, 3720 MA, the Netherlands.
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands.
| | - Lisa Röttjers
- Department of Microbiology, Immunology and Transplantation, Laboratory of Molecular Bacteriology, Rega Institute, Leuven, Belgium
| | - Manoj Fonville
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Antonie van Leeuwenhoeklaan 9, Bilthoven, 3720 MA, the Netherlands
| | - Katshuisa Takumi
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Antonie van Leeuwenhoeklaan 9, Bilthoven, 3720 MA, the Netherlands
| | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Karoline Faust
- Department of Microbiology, Immunology and Transplantation, Laboratory of Molecular Bacteriology, Rega Institute, Leuven, Belgium
| | - Hein Sprong
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Antonie van Leeuwenhoeklaan 9, Bilthoven, 3720 MA, the Netherlands.
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Njoroge MM, Hiscox A, Saddler A, Takken W, van Loon JJA, Fillinger U. Less is more: repellent-treated fabric strips as a substitute for full screening of open eave gaps for indoor and outdoor protection from malaria mosquito bites. Parasit Vectors 2022; 15:259. [PMID: 35858931 PMCID: PMC9297553 DOI: 10.1186/s13071-022-05384-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Accepted: 07/06/2022] [Indexed: 11/10/2022] Open
Abstract
Background Providing protection from malaria vector bites, both indoors and outdoors, is crucial to curbing malaria parasite transmission. Screening of house entry points, especially with incorporated insecticides, confers significant protection but remains a costly and labour-intensive application. Use of spatial repellents has shown promise in creating areas of protection in peri-domestic areas. Methods This study aimed at comparing the protection provided by transfluthrin-treated and untreated complete screens over open eave gaps with incomplete transfluthrin-treated eave strips as a potential replacement for a full screen. Human landing catches were implemented independently inside and outside an experimental hut under controlled semi-field conditions, with insectary-reared Anopheles arabiensis mosquitoes. Results The odds of a female mosquito finding a human volunteer indoors and attempting to bite were similar whether the eaves were completely open or there was an untreated fabric strip fixed around the eaves. However, when the eave gap was completely screened without insecticide, the odds of receiving a bite indoors were reduced by 70% (OR 0.30, 95% CI 0.20–0.47). Adding transfluthrin to the full screen, further increased the protection indoors, with the odds of receiving a bite reduced by 92% (0.08, 95% CI 0.04–0.16) compared to the untreated screen. Importantly, the same protection was conferred when only a narrow transfluthrin-treated fabric strip was loosely fixed around the eave gap (OR 0.07, 95% CI 0.04–0.13). The impact of the transfluthrin treatment on outdoor biting was correlated with evening temperatures during the experiments. At lower evening temperatures, a transfluthrin-treated, complete screen provided moderate and variable protection from bites (OR 0.62, 95% CI 0.37–1.03), whilst at higher evening temperatures the odds of receiving a bite outdoors was over four times lower in the presence of transfluthrin, on either a full screen (OR 0.22 95% 0.12–0.38) or a fabric strip (OR 0.25, 95% 0.15–0.42), than when no treatment was present. Conclusion The findings suggest that transfluthrin-treated fabric strips can provide a substitute for complete eave screens. They are a simple, easy-to-handle tool for protecting people from malaria mosquito bites indoors and potentially around the house in climatic areas where evening and night-time temperatures are relatively high.
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Affiliation(s)
- Margaret Mendi Njoroge
- International Centre of Insect Physiology and Ecology (icipe), Human Health Theme, P.O. Box 30772-00100, Nairobi, Kenya. .,Wageningen University & Research, Laboratory of Entomology, P.O. Box 16, 6700 AA, Wageningen, The Netherlands.
| | - Alexandra Hiscox
- Wageningen University & Research, Laboratory of Entomology, P.O. Box 16, 6700 AA, Wageningen, The Netherlands.,ARCTEC, London School of Hygiene & Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
| | - Adam Saddler
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Socinstrasse 57, 4051 833, Basel, Switzerland.,Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania.,Malaria Atlas Project, Telethon Kids Institute, 15 Hospital Ave, Nedlands, Perth, WA, 6009, Australia
| | - Willem Takken
- Wageningen University & Research, Laboratory of Entomology, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
| | - Joop J A van Loon
- Wageningen University & Research, Laboratory of Entomology, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
| | - Ulrike Fillinger
- International Centre of Insect Physiology and Ecology (icipe), Human Health Theme, P.O. Box 30772-00100, Nairobi, Kenya
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Tizifa TA, Gowelo S, Kabaghe AN, McCann RS, Malenga T, Nkhata RM, Kadama A, Chapeta Y, Takken W, Phiri KS, van Vugt M, van den Berg H, Manda-Taylor L. Community-based house improvement for malaria control in southern Malawi: Stakeholder perceptions, experiences, and acceptability. PLOS Glob Public Health 2022; 2:e0000627. [PMID: 36962454 PMCID: PMC10021647 DOI: 10.1371/journal.pgph.0000627] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Accepted: 05/23/2022] [Indexed: 11/18/2022]
Abstract
House improvement (HI) refers to the full screening or closing of openings such as windows, doors, and eaves, as well as the installation of ceilings, to reduce mosquito-human contact indoors. HI is a viable supplementary intervention that reduces malaria transmission further than the existing strategies alone. In Malawi, HI has not been widely implemented and evaluated for malaria control. Concerns about lack of local evidence, durability in different epidemiological and cultural settings, and the cost of large-scale implementation are among the reasons the strategy is not utilised in many low-income countries. This study assessed community perceptions, experiences, and acceptability of community-led HI in Chikwawa district, southern Malawi. This was a qualitative study where separate focus group discussions were conducted with members from the general community (n = 3); health animators (n = 3); and HI committee members (n = 3). In-depth interviews were conducted with community members (n = 20), and key-informant interviews were conducted with health surveillance assistants and chiefs (n = 23). All interviews were transcribed and coded before performing a thematic content analysis to identify the main themes. Coded data were analysed using Nvivo 12 Plus software. Study participants had a thorough understanding of HI. Participants expressed satisfaction with HI, and they reported enabling factors to HI acceptability, such as the reduction in malaria cases in their villages and the safety and effectiveness of HI use. Participants also reported barriers to effective HI implementation, such as the unavailability and inaccessibility of some HI materials, as well as excessive heat and darkness in HI houses compared to non-HI houses. Participants indicated that they were willing to sustain the intervention but expressed the need for strategies to address barriers to ensure the effectiveness of HI. Our results showed the high knowledge and acceptability of HI by participants in the study area. Intensive and continued health education and community engagement on the significance of HI could help overcome the barriers and improve the acceptability and sustainability of the intervention.
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Affiliation(s)
- Tinashe A. Tizifa
- Division of Internal Medicine, Department of Infectious Diseases, Center for Tropical Medicine and Travel Medicine, University of Amsterdam, Amsterdam University Medical Center, Location Academic Medical Center, Amsterdam, The Netherlands
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Steven Gowelo
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Alinune N. Kabaghe
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Robert S. McCann
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
- Centre for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | - Tumaini Malenga
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
- African Institute for Development Policy, Lilongwe, Malawi
| | - Richard M. Nkhata
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Asante Kadama
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Yankho Chapeta
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
- Biological Sciences Department, Mzuzu University, Mzuzu, Malawi
| | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Kamija S. Phiri
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Michele van Vugt
- Division of Internal Medicine, Department of Infectious Diseases, Center for Tropical Medicine and Travel Medicine, University of Amsterdam, Amsterdam University Medical Center, Location Academic Medical Center, Amsterdam, The Netherlands
| | - Henk van den Berg
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Lucinda Manda-Taylor
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
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8
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Sedda L, McCann RS, Kabaghe AN, Gowelo S, Mburu MM, Tizifa TA, Chipeta MG, van den Berg H, Takken W, van Vugt M, Phiri KS, Cain R, Tangena JAA, Jones CM. Hotspots and super-spreaders: Modelling fine-scale malaria parasite transmission using mosquito flight behaviour. PLoS Pathog 2022; 18:e1010622. [PMID: 35793345 PMCID: PMC9292116 DOI: 10.1371/journal.ppat.1010622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Revised: 07/18/2022] [Accepted: 05/27/2022] [Indexed: 11/19/2022] Open
Abstract
Malaria hotspots have been the focus of public health managers for several years due to the potential elimination gains that can be obtained from targeting them. The identification of hotspots must be accompanied by the description of the overall network of stable and unstable hotspots of malaria, especially in medium and low transmission settings where malaria elimination is targeted. Targeting hotspots with malaria control interventions has, so far, not produced expected benefits. In this work we have employed a mechanistic-stochastic algorithm to identify clusters of super-spreader houses and their related stable hotspots by accounting for mosquito flight capabilities and the spatial configuration of malaria infections at the house level. Our results show that the number of super-spreading houses and hotspots is dependent on the spatial configuration of the villages. In addition, super-spreaders are also associated to house characteristics such as livestock and family composition. We found that most of the transmission is associated with winds between 6pm and 10pm although later hours are also important. Mixed mosquito flight (downwind and upwind both with random components) were the most likely movements causing the spread of malaria in two out of the three study areas. Finally, our algorithm (named MALSWOTS) provided an estimate of the speed of malaria infection progression from house to house which was around 200-400 meters per day, a figure coherent with mark-release-recapture studies of Anopheles dispersion. Cross validation using an out-of-sample procedure showed accurate identification of hotspots. Our findings provide a significant contribution towards the identification and development of optimal tools for efficient and effective spatio-temporal targeted malaria interventions over potential hotspot areas.
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Affiliation(s)
- Luigi Sedda
- Lancaster Ecology and Epidemiology Group, Lancaster Medical School, Lancaster University, United Kingdom
| | - Robert S. McCann
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | - Alinune N. Kabaghe
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Steven Gowelo
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
- MAC Communicable Diseases Action Centre, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Monicah M. Mburu
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Tinashe A. Tizifa
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
- Center for Tropical Medicine and Travel Medicine, University of Amsterdam, The Netherlands
| | - Michael G. Chipeta
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi
| | - Henk van den Berg
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Michèle van Vugt
- Center for Tropical Medicine and Travel Medicine, University of Amsterdam, The Netherlands
| | - Kamija S. Phiri
- School of Global and Public Health, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Russell Cain
- Lancaster Ecology and Epidemiology Group, Lancaster Medical School, Lancaster University, United Kingdom
| | - Julie-Anne A. Tangena
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Christopher M. Jones
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
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9
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van Duijvendijk G, Krijger I, van Schaijk M, Fonville M, Gort G, Sprong H, Takken W. Seasonal dynamics of tick burden and associated Borrelia burgdorferi s.l. and Borrelia miyamotoi infections in rodents in a Dutch forest ecosystem. Exp Appl Acarol 2022; 87:235-251. [PMID: 35840866 PMCID: PMC9424142 DOI: 10.1007/s10493-022-00720-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 05/11/2022] [Indexed: 05/25/2023]
Abstract
Ixodes ricinus ticks transmit Borrelia burgdorferi sensu lato (s.l.) as well as Borrelia miyamotoi. Larvae become infected when feeding on infected rodents, with horizontal transmission of B. burgdorferi and horizontal and vertical transmission of B. miyamotoi. We studied seasonal dynamics of infection rates of I. ricinus and their rodent hosts, and hence transmission risk of these two distinctly different Borrelia species. Rodents were live-trapped and inspected for ticks from May to November in 2013 and 2014 in a forest in The Netherlands. Trapped rodents were temporarily housed in the laboratory and detached ticks were collected. Borrelia infections were determined from the trapped rodents and collected ticks. Borrelia burgdorferi s.l. and B. miyamotoi were found in ticks as well as in rodents. Rodent density was higher in 2014, whereas tick burden as well as the Borrelia infection rates in rodents were higher in 2013. The density of B. miyamotoi-infected nymphs did not differ between the years. Tick burdens were higher on Apodemus sylvaticus than on Myodes glareolus, and higher on males than on females. Borrelia-infection rate of rodents varied strongly seasonally, peaking in summer. As the larval tick burden also peaked in summer, the generation of infected nymphs was highest in summer. We conclude that the heterogeneity of environmental and host-specific factors affects the seasonal transmission of Borrelia spp., and that these effects act more strongly on horizontally transmitted B. burgdorferi spp. than on the vertically transmitted B. miyamotoi.
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Affiliation(s)
- Gilian van Duijvendijk
- Laboratory of Entomology, Wageningen University, PO box 16, 6700 AA, Wageningen, The Netherlands
- Wageningen Environmental Research, Wageningen University and Research, PO box 47, 6700 AA, Wageningen, The Netherlands
| | - Inge Krijger
- Laboratory of Entomology, Wageningen University, PO box 16, 6700 AA, Wageningen, The Netherlands
- Stichting Kennis- en Adviescentrum Dierplagen (KAD), Nudepark 145, 6702 DZ, Wageningen, The Netherlands
| | - Marloes van Schaijk
- Laboratory of Entomology, Wageningen University, PO box 16, 6700 AA, Wageningen, The Netherlands
- Koppert Biological Systems, Industrieweg 14, 2651 BE, Berkel en Rodenrijs, The Netherlands
| | - Manoj Fonville
- Laboratory for Zoonosis and Environmental Microbiology, National Institute for Public Health and the Environment (RIVM), P.O. Box 1, 3720 BA, Bilthoven, The Netherlands
| | - Gerrit Gort
- Mathematical and Statistical Methods, Wageningen University, PO box 16, 6700 AA, Wageningen, The Netherlands
| | - Hein Sprong
- Laboratory of Entomology, Wageningen University, PO box 16, 6700 AA, Wageningen, The Netherlands
- Laboratory for Zoonosis and Environmental Microbiology, National Institute for Public Health and the Environment (RIVM), P.O. Box 1, 3720 BA, Bilthoven, The Netherlands
| | - Willem Takken
- Laboratory of Entomology, Wageningen University, PO box 16, 6700 AA, Wageningen, The Netherlands.
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10
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Murindahabi MM, Takken W, Hakizimana E, van Vliet AJH, Poortvliet PM, Mutesa L, Koenraadt CJM. A handmade trap for malaria mosquito surveillance by citizens in Rwanda. PLoS One 2022; 17:e0266714. [PMID: 35544478 PMCID: PMC9094558 DOI: 10.1371/journal.pone.0266714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 03/27/2022] [Indexed: 11/18/2022] Open
Abstract
For effective sampling of mosquitoes in malaria surveillance programmes, it is essential to include attractive cues in traps. With the aim of implementing a citizen science project on malaria vectors in rural Rwanda, a handmade plastic bottle trap was designed and tested in the field to determine its effectiveness in capturing adult Anopheles gambiae sensu lato, the main malaria vector, and other mosquito species. Carbon dioxide (CO2) and light were used as attractive cues. CO2 was produced by inoculating sugar with yeast and water. Light was emitted from a torch by light-emitting diodes (LEDs). Under field conditions in rural Rwanda, three handmade trap designs were compared to Centers for Disease Control and Prevention miniature light traps (CDC-LT) in houses. The trap baited with yeast produced CO2 and light caught the highest number of mosquitoes compared to the traps baited with light alone or CO2 alone. The number of An. gambiae s.l. in the handmade trap with light and CO2 was approximately 9–10% of the number caught with a CDC light trap. This suggests that about 10 volunteers with a handmade trap could capture a similar-sized sample of An. gambiae as one CDC-LT would collect. Based on these findings, the handmade plastic bottle trap baited with sugar fermenting yeast and light represents an option for inclusion in mosquito surveillance activities in a citizen science context.
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Affiliation(s)
- Marilyn M. Murindahabi
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
- College of Sciences and Technology, University of Rwanda, Kigali, Rwanda
| | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Emmanuel Hakizimana
- Malaria and other Parasitic Diseases Division, Rwanda Biomedical Center, Kigali, Rwanda
| | - Arnold J. H. van Vliet
- Environmental Systems Analysis Group, Wageningen University & Research, Wageningen, The Netherlands
| | - P. Marijn Poortvliet
- Strategic Communication group, Wageningen University & Research, Wageningen, The Netherlands
| | - Leon Mutesa
- College of Medicine and Health Sciences, University of Rwanda, Kigali, Rwanda
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11
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Amoah B, McCann RS, Kabaghe AN, Mburu M, Chipeta MG, Moraga P, Gowelo S, Tizifa T, van den Berg H, Mzilahowa T, Takken W, van Vugt M, Phiri KS, Diggle PJ, Terlouw DJ, Giorgi E. Identifying Plasmodium falciparum transmission patterns through parasite prevalence and entomological inoculation rate. eLife 2021; 10:65682. [PMID: 34672946 PMCID: PMC8530514 DOI: 10.7554/elife.65682] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Accepted: 09/30/2021] [Indexed: 11/13/2022] Open
Abstract
Background Monitoring malaria transmission is a critical component of efforts to achieve targets for elimination and eradication. Two commonly monitored metrics of transmission intensity are parasite prevalence (PR) and the entomological inoculation rate (EIR). Comparing the spatial and temporal variations in the PR and EIR of a given geographical region and modelling the relationship between the two metrics may provide a fuller picture of the malaria epidemiology of the region to inform control activities. Methods Using geostatistical methods, we compare the spatial and temporal patterns of Plasmodium falciparum EIR and PR using data collected over 38 months in a rural area of Malawi. We then quantify the relationship between EIR and PR by using empirical and mechanistic statistical models. Results Hotspots identified through the EIR and PR partly overlapped during high transmission seasons but not during low transmission seasons. The estimated relationship showed a 1-month delayed effect of EIR on PR such that at lower levels of EIR, increases in EIR are associated with rapid rise in PR, whereas at higher levels of EIR, changes in EIR do not translate into notable changes in PR. Conclusions Our study emphasises the need for integrated malaria control strategies that combine vector and human host managements monitored by both entomological and parasitaemia indices. Funding This work was supported by Stichting Dioraphte grant number 13050800.
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Affiliation(s)
- Benjamin Amoah
- Centre for Health Informatics, Computing, and Statistics (CHICAS), Lancaster Medical School, Lancaster University, Lancaster, United Kingdom
| | - Robert S McCann
- Laboratory of Entomology, Wageningen University and Research, Wageningen, Netherlands.,Department of Public Health, College of Medicine, University of Malawi, Blantyre, Malawi.,Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, United States
| | - Alinune N Kabaghe
- Department of Public Health, College of Medicine, University of Malawi, Blantyre, Malawi.,Academic Medical Centre, University of Amsterdam, Amsterdam, Netherlands
| | - Monicah Mburu
- Laboratory of Entomology, Wageningen University and Research, Wageningen, Netherlands.,Department of Public Health, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Michael G Chipeta
- Department of Public Health, College of Medicine, University of Malawi, Blantyre, Malawi.,Malawi-Liverpool Wellcome Trust Research Programme, Blantyre, Malawi.,Big Data Institute, University of Oxford, Oxford, United Kingdom
| | - Paula Moraga
- Centre for Health Informatics, Computing, and Statistics (CHICAS), Lancaster Medical School, Lancaster University, Lancaster, United Kingdom.,Computer, Electrical and Mathematical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
| | - Steven Gowelo
- Laboratory of Entomology, Wageningen University and Research, Wageningen, Netherlands.,Department of Public Health, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Tinashe Tizifa
- Department of Public Health, College of Medicine, University of Malawi, Blantyre, Malawi.,Academic Medical Centre, University of Amsterdam, Amsterdam, Netherlands
| | - Henk van den Berg
- Laboratory of Entomology, Wageningen University and Research, Wageningen, Netherlands
| | - Themba Mzilahowa
- Department of Public Health, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Willem Takken
- Laboratory of Entomology, Wageningen University and Research, Wageningen, Netherlands
| | - Michele van Vugt
- Academic Medical Centre, University of Amsterdam, Amsterdam, Netherlands
| | - Kamija S Phiri
- Department of Public Health, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Peter J Diggle
- Centre for Health Informatics, Computing, and Statistics (CHICAS), Lancaster Medical School, Lancaster University, Lancaster, United Kingdom
| | - Dianne J Terlouw
- Department of Public Health, College of Medicine, University of Malawi, Blantyre, Malawi.,Malawi-Liverpool Wellcome Trust Research Programme, Blantyre, Malawi.,Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Emanuele Giorgi
- Centre for Health Informatics, Computing, and Statistics (CHICAS), Lancaster Medical School, Lancaster University, Lancaster, United Kingdom
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12
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Multerer L, Vanobberghen F, Glass TR, Hiscox A, Lindsay SW, Takken W, Tiono A, Smith T. Estimating intervention effectiveness in trials of malaria interventions with contamination. Malar J 2021; 20:413. [PMID: 34670558 PMCID: PMC8527711 DOI: 10.1186/s12936-021-03924-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Accepted: 09/21/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In cluster randomized trials (CRTs) or stepped wedge cluster randomized trials (SWCRTs) of malaria interventions, mosquito movement leads to contamination between trial arms unless buffer zones separate the clusters. Contamination can be accounted for in the analysis, yielding an estimate of the contamination range, the distance over which contamination measurably biases the effectiveness. METHODS A previously described analysis for CRTs is extended to SWCRTs and estimates of effectiveness are provided as a function of intervention coverage. The methods are applied to two SWCRTs of malaria interventions, the SolarMal trial on the impact of mass trapping of mosquitoes with odor-baited traps and the AvecNet trial on the effect of adding pyriproxyfen to long-lasting insecticidal nets. RESULTS For the SolarMal trial, the contamination range was estimated to be 146 m ([Formula: see text] credible interval [Formula: see text] km), together with a [Formula: see text] ([Formula: see text] credible interval [Formula: see text]) reduction of Plasmodium infection, compared to the [Formula: see text] reduction estimated without accounting for contamination. The estimated effectiveness had an approximately linear relationship with coverage. For the AvecNet trial, estimated contamination effects were minimal, with insufficient data from the cluster boundary regions to estimate the effectiveness as a function of coverage. CONCLUSIONS The contamination range in these trials of malaria interventions is much less than the distances Anopheles mosquitoes can fly. An appropriate analysis makes buffer zones unnecessary, enabling the design of more cost-efficient trials. Estimation of the contamination range requires information from the cluster boundary regions and trials should be designed to collect this.
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Affiliation(s)
- Lea Multerer
- Swiss Tropical and Public Health Institute, Basel, Switzerland. .,University of Basel, Basel, Switzerland.
| | - Fiona Vanobberghen
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Tracy R Glass
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Alexandra Hiscox
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands.,ARCTEC, London School of Hygiene and Tropical Medicine, London, UK
| | | | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Alfred Tiono
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Thomas Smith
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
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13
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Mburu MM, Zembere K, Mzilahowa T, Terlouw AD, Malenga T, van den Berg H, Takken W, McCann RS. Impact of cattle on the abundance of indoor and outdoor resting malaria vectors in southern Malawi. Malar J 2021; 20:353. [PMID: 34446033 PMCID: PMC8390081 DOI: 10.1186/s12936-021-03885-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Accepted: 08/16/2021] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Understanding the blood feeding preferences and resting habits of malaria vectors is important for assessing and designing effective malaria vector control tools. The presence of livestock, such as cattle, which are used as blood meal hosts by some malaria vectors, may impact malaria parasite transmission dynamics. The presence of livestock may provide sufficient blood meals for the vectors, thereby reducing the frequency of vectors biting humans. Alternatively, the presence of cattle may enhance the availability of blood meals such that infectious mosquitoes may survive longer, thereby increasing the risk of malaria transmission. This study assessed the effect of household-level cattle presence and distribution on the abundance of indoor and outdoor resting malaria vectors. METHODS Houses with and without cattle were selected in Chikwawa district, southern Malawi for sampling resting malaria vectors. Prokopack aspirators and clay pots were used for indoor and outdoor sampling, respectively. Each house was sampled over two consecutive days. For houses with cattle nearby, the number of cattle and the distances from the house to where the cattle were corralled the previous night were recorded. All data were analysed using generalized linear models fitted with Poisson distribution. RESULTS The malaria vectors caught resting indoors were Anopheles gambiae sensu stricto (s.s.), Anopheles arabiensis and Anopheles funestus s.s. Outdoor collections consisted primarily of An. arabiensis. The catch sizes of indoor resting An. gambiae sensu lato (s.l.) were not different in houses with and without cattle (P = 0.34). The presence of cattle near a house was associated with a reduction in the abundance of indoor resting An. funestus s.l. (P = 0.04). This effect was strongest when cattle were kept overnight ≤ 15 m away from the houses (P = 0.03). The blood meal hosts varied across the species. CONCLUSION These results highlight differences between malaria vector species and their interactions with potential blood meal hosts, which may have implications for malaria risk. Whereas An. arabiensis remained unaffected, the reduction of An. funestus s.s. in houses near cattle suggests a potential protective effect of cattle. However, the low abundance of mosquitoes reduced the power of some analyses and limited the generalizability of the results to other settings. Therefore, further studies incorporating the vectors' host-seeking behaviour/human biting rates are recommended to fully support the primary finding.
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Affiliation(s)
- Monicah M Mburu
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi.
- Laboratory of Entomology, Wageningen University and Research, Wageningen, The Netherlands.
- Macha Research Trust, Choma, Zambia.
| | - Kennedy Zembere
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
- Malawi-Liverpool-Wellcome Trust, Blantyre, Malawi
| | - Themba Mzilahowa
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
- MAC Communicable Diseases Action Centre, Blantyre, Malawi
| | - Anja D Terlouw
- Malawi-Liverpool-Wellcome Trust, Blantyre, Malawi
- Liverpool School of Tropical Medicine, Liverpool, UK
| | - Tumaini Malenga
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Henk van den Berg
- Laboratory of Entomology, Wageningen University and Research, Wageningen, The Netherlands
| | - Willem Takken
- Laboratory of Entomology, Wageningen University and Research, Wageningen, The Netherlands
| | - Robert S McCann
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
- Laboratory of Entomology, Wageningen University and Research, Wageningen, The Netherlands
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, USA
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14
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Phiri MD, McCann RS, Kabaghe AN, van den Berg H, Malenga T, Gowelo S, Tizifa T, Takken W, van Vugt M, Phiri KS, Terlouw DJ, Worrall E. Cost of community-led larval source management and house improvement for malaria control: a cost analysis within a cluster-randomized trial in a rural district in Malawi. Malar J 2021; 20:268. [PMID: 34120608 PMCID: PMC8200285 DOI: 10.1186/s12936-021-03800-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Accepted: 06/03/2021] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND House improvement (HI) to prevent mosquito house entry, and larval source management (LSM) targeting aquatic mosquito stages to prevent development into adult forms, are promising complementary interventions to current malaria vector control strategies. Lack of evidence on costs and cost-effectiveness of community-led implementation of HI and LSM has hindered wide-scale adoption. This study presents an incremental cost analysis of community-led implementation of HI and LSM, in a cluster-randomized, factorial design trial, in addition to standard national malaria control interventions in a rural area (25,000 people), in southern Malawi. METHODS In the trial, LSM comprised draining, filling, and Bacillus thuringiensis israelensis-based larviciding, while house improvement (henceforth HI) involved closing of eaves and gaps on walls, screening windows/ventilation spaces with wire mesh, and doorway modifications. Communities implemented all interventions. Costs were estimated retrospectively using the 'ingredients approach', combining 'bottom-up' and 'top-down approaches', from the societal perspective. To estimate the cost of independently implementing each intervention arm, resources shared between trial arms (e.g. overheads) were allocated to each consuming arm using proxies developed based on share of resource input quantities consumed. Incremental implementation costs (in 2017 US$) are presented for HI-only, LSM-only and HI + LSM arms. In sensitivity analyses, the effect of varying costs of important inputs on estimated costs was explored. RESULTS The total economic programme costs of community-led HI and LSM implementation was $626,152. Incremental economic implementation costs of HI, LSM and HI + LSM were estimated as $27.04, $25.06 and $33.44, per person per year, respectively. Project staff, transport and labour costs, but not larvicide or screening material, were the major cost drivers across all interventions. Costs were sensitive to changes in staff costs and population covered. CONCLUSIONS In the trial, the incremental economic costs of community-led HI and LSM implementation were high compared to previous house improvement and LSM studies. Several factors, including intervention design, year-round LSM implementation and low human population density could explain the high costs. The factorial trial design necessitated use of proxies to allocate costs shared between trial arms, which limits generalizability where different designs are used. Nevertheless, costs may inform planners of similar intervention packages where cost-effectiveness is known. Trial registration Not applicable. The original trial was registered with The Pan African Clinical Trials Registry on 3 March 2016, trial number PACTR201604001501493.
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Affiliation(s)
- Mphatso Dennis Phiri
- Malaria Epidemiology Group, Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi.
| | - Robert S McCann
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, USA
| | - Alinune Nathanael Kabaghe
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Henk van den Berg
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Tumaini Malenga
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Steven Gowelo
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Tinashe Tizifa
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Michèle van Vugt
- Center for Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Division of Internal Medicine, Amsterdam-UMC, Location AMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Kamija S Phiri
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Dianne J Terlouw
- Malaria Epidemiology Group, Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi
- Liverpool School of Tropical Medicine, Liverpool, UK
| | - Eve Worrall
- Liverpool School of Tropical Medicine, Liverpool, UK
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McCann RS, Kabaghe AN, Moraga P, Gowelo S, Mburu MM, Tizifa T, Chipeta MG, Nkhono W, Di Pasquale A, Maire N, Manda-Taylor L, Mzilahowa T, van den Berg H, Diggle PJ, Terlouw DJ, Takken W, van Vugt M, Phiri KS. The effect of community-driven larval source management and house improvement on malaria transmission when added to the standard malaria control strategies in Malawi: a cluster-randomized controlled trial. Malar J 2021; 20:232. [PMID: 34022912 PMCID: PMC8140568 DOI: 10.1186/s12936-021-03769-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 05/12/2021] [Indexed: 11/21/2022] Open
Abstract
BACKGROUND Current standard interventions are not universally sufficient for malaria elimination. The effects of community-based house improvement (HI) and larval source management (LSM) as supplementary interventions to the Malawi National Malaria Control Programme (NMCP) interventions were assessed in the context of an intensive community engagement programme. METHODS The study was a two-by-two factorial, cluster-randomized controlled trial in Malawi. Village clusters were randomly assigned to four arms: a control arm; HI; LSM; and HI + LSM. Malawi NMCP interventions and community engagement were used in all arms. Household-level, cross-sectional surveys were conducted on a rolling, 2-monthly basis to measure parasitological and entomological outcomes over 3 years, beginning with one baseline year. The primary outcome was the entomological inoculation rate (EIR). Secondary outcomes included mosquito density, Plasmodium falciparum prevalence, and haemoglobin levels. All outcomes were assessed based on intention to treat, and comparisons between trial arms were conducted at both cluster and household level. RESULTS Eighteen clusters derived from 53 villages with 4558 households and 20,013 people were randomly assigned to the four trial arms. The mean nightly EIR fell from 0.010 infectious bites per person (95% CI 0.006-0.015) in the baseline year to 0.001 (0.000, 0.003) in the last year of the trial. Over the full trial period, the EIR did not differ between the four trial arms (p = 0.33). Similar results were observed for the other outcomes: mosquito density and P. falciparum prevalence decreased over 3 years of sampling, while haemoglobin levels increased; and there were minimal differences between the trial arms during the trial period. CONCLUSIONS In the context of high insecticide-treated bed net use, neither community-based HI, LSM, nor HI + LSM contributed to further reductions in malaria transmission or prevalence beyond the reductions observed over two years across all four trial arms. This was the first trial, as far as the authors are aware, to test the potential complementary impact of LSM and/or HI beyond levels achieved by standard interventions. The unexpectedly low EIR values following intervention implementation indicated a promising reduction in malaria transmission for the area, but also limited the usefulness of this outcome for measuring differences in malaria transmission among the trial arms. Trial registration PACTR, PACTR201604001501493, Registered 3 March 2016, https://pactr.samrc.ac.za/ .
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Affiliation(s)
- Robert S McCann
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, USA
| | - Alinune N Kabaghe
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
- Center for Tropical Medicine & Travel Medicine, Department of Infectious Diseases, Division of Internal Medicine, University of Amsterdam, Amsterdam, The Netherlands
| | - Paula Moraga
- CHICAS, Lancaster Medical School, Lancaster University, Lancaster, UK
- Computer, Electrical and Mathematical Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
| | - Steven Gowelo
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Monicah M Mburu
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Tinashe Tizifa
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
- Center for Tropical Medicine & Travel Medicine, Department of Infectious Diseases, Division of Internal Medicine, University of Amsterdam, Amsterdam, The Netherlands
| | - Michael G Chipeta
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
- CHICAS, Lancaster Medical School, Lancaster University, Lancaster, UK
- Big Data Institute, University of Oxford, Oxford, UK
- Malawi-Liverpool Wellcome Trust Clinical Research Program, Blantyre, Malawi
| | - William Nkhono
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Aurelio Di Pasquale
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Nicolas Maire
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Lucinda Manda-Taylor
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Themba Mzilahowa
- MAC Communicable Diseases Action Centre, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Henk van den Berg
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Peter J Diggle
- CHICAS, Lancaster Medical School, Lancaster University, Lancaster, UK
| | - Dianne J Terlouw
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
- Malawi-Liverpool Wellcome Trust Clinical Research Program, Blantyre, Malawi
- Clinical Sciences Department, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Michèle van Vugt
- Center for Tropical Medicine & Travel Medicine, Department of Infectious Diseases, Division of Internal Medicine, University of Amsterdam, Amsterdam, The Netherlands
| | - Kamija S Phiri
- School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi.
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Athrey G, Popkin-Hall ZR, Takken W, Slotman MA. The Expression of Chemosensory Genes in Male Maxillary Palps of Anopheles coluzzii (Diptera: Culicidae) and An. quadriannulatus. J Med Entomol 2021; 58:1012-1020. [PMID: 33576414 PMCID: PMC8122237 DOI: 10.1093/jme/tjaa290] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Indexed: 06/12/2023]
Abstract
Because of its importance as a malaria vector, Anopheles coluzzii's Coetzee & Wilkerson olfactory system has been studied extensively. Among this work is a series of studies comparing the expression of chemosensory genes in olfactory organs in females and/or males of these species. These have identified species- and female-biased chemosensory gene expression patterns. However, many questions remain about the role of chemosensation in male anopheline biology. To pave the way for future work we used RNAseq to compare chemosensory gene expression in the male maxillary palps of An. coluzzii and its sibling species An. quadriannulatus Theobald. As expected, the chemosensory gene repertoire is small in the male maxillary palps. Both species express the tuning receptors Or8 and Or28 at relatively high levels. The CO2 receptor genes Gr22-Gr24 are present in both species as well, although at much lower level than in females. Additionally, several chemoreceptors are species-specific. Gr37 and Gr52 are exclusive to An. coluzzii, whereas Or9 and Gr60 were detected only in An. quadriannulatus. Furthermore, several chemosensory genes show differential expression between the two species. Finally, several Irs, Grs, and Obps that show strong differential expression in the female palps, are absent or lowly expressed in the male palps. While many questions remain about the role of chemosensation in anopheline male biology, these results suggest that the male maxillary palps could have both a sex- and species-specific role in the perception of chemical stimuli. This work may guide future studies on the role of the male maxillary palp in these species.
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Affiliation(s)
- Giridhar Athrey
- Department of Poultry Science, Texas A&M University, College Station, TX
| | | | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Michel A Slotman
- Department of Entomology, Texas A&M University, College Station, TX
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Mwingira VS, Mboera LEG, Takken W. Synergism between nonane and emanations from soil as cues in oviposition-site selection of natural populations of Anopheles gambiae and Culex quinquefasciatus. Malar J 2021; 20:52. [PMID: 33478526 PMCID: PMC7819190 DOI: 10.1186/s12936-020-03575-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Accepted: 12/31/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Olfactory cues have been shown to have an important role in guiding gravid mosquito females to selected sites for egg laying. The objective of this study was to determine the influence of emanations from soil from a breeding site and the putative oviposition pheromone nonane on oviposition-site selection of natural populations of Anopheles gambiae sensu lato (s.l.) and Culex quinquefasciatus. METHODS This field-based study was conducted in Mvomero District in East-central Tanzania. In a dual-choice experimental set up, clay bowls were dug into the ground and filled with one of the following treatments: (i) distilled water + autoclaved soil (control), (ii) distilled water + soil from a natural mosquito breeding site, (iii) distilled water + nonane and (iv) distilled water + nonane + soil from a natural breeding site. Soil was dried and autoclaved or dried only before use. After five days of incubation, larvae were collected daily for 10 days. The median number of larvae per bowl per day was used as outcome measure. RESULTS Autoclaved soil had a significant attractive effect on oviposition behaviour of Cx. quinquefasciatus (median values ± s.e: 8.0 ± 1.1; P < 0.005) but no effect on An. gambiae (median value ± s.e: 0.0 ± 0.2; P = 0.18). Nonane and emanations from untreated soil significantly and positively influenced the selection of oviposition sites by both An. gambiae s.l. (median values ± s.e.: 12.0 ± 2.0 and 4.5 ± 1.5, respectively; P < 0.0001) and Cx. quinquefasciatus (median values ± s.e.: 19.0 ± 1.3 and 17.0 ± 2.0, respectively; P < 0.0001). A mixture of nonane and untreated soil caused a synergistic effect on oviposition behaviour in An. gambiae s.l. (median value ± s.e.: 23.5 ± 2.5; P < 0.0001) compared to either nonane (median values ± s.e.: 12.0 ± 2.0; P < 0.0001) or untreated soil alone (median value ± s.e.: 4.5 ± 1.5; P < 0.0001). A synergistic effect of nonane mixed with untreated soil was also found in Cx. quinquefasciatus (median value ± s.e.: 41.0 ± 2.1; P < 0.0001) compared to either nonane (median value ± s.e. 19.0 ± 1.3; P < 0.0001) or untreated soil alone (median value ± s.e.: 17.0 ± 2.0; P < 0.0001). The oviposition activity index for An. gambiae was 0.56 (P < 0.001) and for Cx. quinquefasciatus 0.59 (P < 0.0001). CONCLUSIONS The larval pheromone nonane and emanations from breeding-site soil both induced oviposition in wild An. gambiae s.l. and Cx. quinquefasciatus, with a synergistic effect when both stimuli were present simultaneously. This is the first study in which nonane is shown to cause oviposition under natural conditions, suggesting that this compound can potentially be exploited for the management of mosquito vectors.
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Affiliation(s)
- Victor S Mwingira
- Laboratory of Entomology, Wageningen University & Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands.,SACIDS Foundation for One Health, Sokoine University of Agriculture, Chuo Kikuu, P.O. Box 3297, Morogoro, Tanzania
| | - Leonard E G Mboera
- SACIDS Foundation for One Health, Sokoine University of Agriculture, Chuo Kikuu, P.O. Box 3297, Morogoro, Tanzania
| | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands.
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Njoroge MM, Fillinger U, Saddler A, Moore S, Takken W, van Loon JJA, Hiscox A. Evaluating putative repellent 'push' and attractive 'pull' components for manipulating the odour orientation of host-seeking malaria vectors in the peri-domestic space. Parasit Vectors 2021; 14:42. [PMID: 33430963 PMCID: PMC7802213 DOI: 10.1186/s13071-020-04556-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 12/16/2020] [Indexed: 12/17/2022] Open
Abstract
Background Novel malaria vector control approaches aim to combine tools for maximum protection. This study aimed to evaluate novel and re-evaluate existing putative repellent ‘push’ and attractive ‘pull’ components for manipulating the odour orientation of malaria vectors in the peri-domestic space. Methods Anopheles arabiensis outdoor human landing catches and trap comparisons were implemented in large semi-field systems to (i) test the efficacy of Citriodiol® or transfluthrin-treated fabric strips positioned in house eave gaps as push components for preventing bites; (ii) understand the efficacy of MB5-baited Suna-traps in attracting vectors in the presence of a human being; (iii) assess 2-butanone as a CO2 replacement for trapping; (iv) determine the protection provided by a full push-pull set up. The air concentrations of the chemical constituents of the push–pull set-up were quantified. Results Microencapsulated Citriodiol® eave strips did not provide outdoor protection against host-seeking An. arabiensis. Transfluthrin-treated strips reduced the odds of a mosquito landing on the human volunteer (OR 0.17; 95% CI 0.12–0.23). This impact was lower (OR 0.59; 95% CI 0.52–0.66) during the push-pull experiment, which was associated with low nighttime temperatures likely affecting the transfluthrin vaporisation. The MB5-baited Suna trap supplemented with CO2 attracted only a third of the released mosquitoes in the absence of a human being; however, with a human volunteer in the same system, the trap caught < 1% of all released mosquitoes. The volunteer consistently attracted over two-thirds of all mosquitoes released. This was the case in the absence (‘pull’ only) and in the presence of a spatial repellent (‘push-pull’), indicating that in its current configuration the tested ‘pull’ does not provide a valuable addition to a spatial repellent. The chemical 2-butanone was ineffective in replacing CO2. Transfluthrin was detectable in the air space but with a strong linear reduction in concentrations over 5 m from release. The MB5 constituent chemicals were only irregularly detected, potentially suggesting insufficient release and concentration in the air for attraction. Conclusion This step-by-step evaluation of the selected ‘push’ and ‘pull’ components led to a better understanding of their ability to affect host-seeking behaviours of the malaria vector An. arabiensis in the peri-domestic space and helps to gauge the impact such tools would have when used in the field for monitoring or control.![]()
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Affiliation(s)
- Margaret Mendi Njoroge
- International Centre of Insect Physiology and Ecology (icipe), Human Health Theme, Nairobi, 00100, Kenya.,Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
| | - Ulrike Fillinger
- International Centre of Insect Physiology and Ecology (icipe), Human Health Theme, Nairobi, 00100, Kenya.
| | - Adam Saddler
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Socinstrasse 57, 4051 833, Basel, Switzerland.,University of Basel, Petersplatz 1, Basel, Switzerland.,Department of Environmental Health and Ecological Sciences, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania
| | - Sarah Moore
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Socinstrasse 57, 4051 833, Basel, Switzerland.,University of Basel, Petersplatz 1, Basel, Switzerland.,Department of Environmental Health and Ecological Sciences, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania
| | - Willem Takken
- Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
| | - Joop J A van Loon
- Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
| | - Alexandra Hiscox
- International Centre of Insect Physiology and Ecology (icipe), Human Health Theme, Nairobi, 00100, Kenya.,Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands.,London School of Hygiene and Tropical Medicine, ARCTEC, Keppel Street, London, WC1E 7HT, UK
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19
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Murindahabi MM, Takken W, Misago X, Niyituma E, Umupfasoni J, Hakizimana E, van Vliet AJH, Poortvliet PM, Mutesa L, Murindahabi NK, Koenraadt CJM. Monitoring mosquito nuisance for the development of a citizen science approach for malaria vector surveillance in Rwanda. Malar J 2021; 20:36. [PMID: 33423679 PMCID: PMC7798336 DOI: 10.1186/s12936-020-03579-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Accepted: 12/31/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Many countries, including Rwanda, have mosquito monitoring programmes in place to support decision making in the fight against malaria. However, these programmes can be costly, and require technical (entomological) expertise. Involving citizens in data collection can greatly support such activities, but this has not yet been thoroughly investigated in a rural African context. METHODS Prior to the implementation of such a citizen-science approach, a household entomological survey was conducted in October-November 2017 and repeated one year later in Busoro and Ruhuha sectors, in southern and eastern province of Rwanda, respectively. The goal was to evaluate the perception of mosquito nuisance reported by citizens as a potential indicator for malaria vector hotspots. Firstly, mosquito abundance and species composition were determined using Centers for Disease Control and Prevention (CDC) light traps inside the houses. Secondly, household members were interviewed about malaria risk factors and their perceived level of mosquito nuisance. RESULTS Tiled roofs, walls made of mud and wood, as well as the number of occupants in the house were predictors for the number of mosquitoes (Culicidae) in the houses, while the presence of eaves plus walls made of mud and wood were predictors for malaria vector abundance. Perception of mosquito nuisance reported indoors tended to be significantly correlated with the number of Anopheles gambiae sensu lato (s.l.) and Culicidae collected indoors, but this varied across years and sectors. At the village level, nuisance also significantly correlated with An. gambiae s.l. and total mosquito density, but only in 2018 while not in 2017. CONCLUSIONS Perception of mosquito nuisance denoted in a questionnaire survey could be used as a global indicator of malaria vector hotspots. Hence, involving citizens in such activities can complement malaria vector surveillance and control.
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Affiliation(s)
- Marilyn Milumbu Murindahabi
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands.,College of Sciences and Technology, University of Rwanda, Kigali, Rwanda
| | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Xavier Misago
- Malaria and Other Parasitic Diseases Division, Rwanda Biomedical Center, Kigali, Rwanda
| | - Elias Niyituma
- Malaria and Other Parasitic Diseases Division, Rwanda Biomedical Center, Kigali, Rwanda
| | - Jackie Umupfasoni
- Malaria and Other Parasitic Diseases Division, Rwanda Biomedical Center, Kigali, Rwanda
| | - Emmanuel Hakizimana
- Malaria and Other Parasitic Diseases Division, Rwanda Biomedical Center, Kigali, Rwanda
| | - Arnold J H van Vliet
- Environmental Systems Analysis Group, Wageningen University & Research, Wageningen, The Netherlands
| | - P Marijn Poortvliet
- Strategic Communication Group, Wageningen University & Research, Wageningen, the Netherlands
| | - Leon Mutesa
- College of Medicine and Health Sciences, University of Rwanda, Kigali, Rwanda
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Mwingira V, Mboera LEG, Dicke M, Takken W. Exploiting the chemical ecology of mosquito oviposition behavior in mosquito surveillance and control: a review. J Vector Ecol 2020; 45:155-179. [PMID: 33207066 DOI: 10.1111/jvec.12387] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Vector control is an important component of the interventions aimed at mosquito-borne disease control. Current and future mosquito control strategies are likely to rely largely on the understanding of the behavior of the vector, by exploiting mosquito biology and behavior, while using cost-effective, carefully timed larvicidal and high-impact, low-volume adulticidal applications. Here we review the knowledge on the ecology of mosquito oviposition behavior with emphasis on the potential role of infochemicals in surveillance and control of mosquito-borne diseases. A search of PubMed, Embase, Web of Science, Global Health Archive, and Google Scholar databases was conducted using the keywords mosquito, infochemical, pheromone, kairomone, allomone, synomone, apneumone, attractant, host-seeking, and oviposition. Articles in English from 1974 to 2019 were reviewed to gain comprehensive understanding of current knowledge on infochemicals in mosquito resource-searching behavior. Oviposition of many mosquito species is mediated by infochemicals that comprise pheromones, kairomones, synomones, allomones, and apneumones. The novel putative infochemicals that mediate oviposition in the mosquito subfamilies Anophelinae and Culicinae were identified. The role of infochemicals in surveillance and control of these and other mosquito tribes is discussed with respect to origin of the chemical cues and how these affect gravid mosquitoes. Oviposition attractants and deterrents can potentially be used for manipulation of mosquito behavior by making protected resources unsuitable for mosquitoes (push) while luring them towards attractive sources (pull). In this review, strategies of targeting breeding sites with environmentally friendly larvicides with the aim to develop appropriate trap-and-kill techniques are discussed.
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Affiliation(s)
- Victor Mwingira
- Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
- National Institute for Medical Research, Amani Research Centre, P.O. Box 81, Muheza, Tanzania
| | - Leonard E G Mboera
- SACIDS Foundation for One Health, Sokoine University of Agriculture, P.O. Box 3297 Chuo Kikuu, Morogoro, Tanzania
| | - Marcel Dicke
- Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
| | - Willem Takken
- Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
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Gowelo S, Chirombo J, Koenraadt CJ, Mzilahowa T, van den Berg H, Takken W, McCann RS. Characterisation of anopheline larval habitats in southern Malawi. Acta Trop 2020; 210:105558. [PMID: 32485166 DOI: 10.1016/j.actatropica.2020.105558] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 05/22/2020] [Accepted: 05/22/2020] [Indexed: 10/24/2022]
Abstract
INTRODUCTION Increasing the knowledgebase of anopheline larval ecology could enable targeted deployment of malaria control efforts and consequently reduce costs of implementation. In Malawi, there exists a knowledge gap in anopheline larval ecology and, therefore, basis for targeted deployment of larval source management (LSM) for malaria control, specifically larvicides. We set out to characterize anopheline larval habitats in the Majete area of Malawi on the basis of habitat ecology and anopheline larval productivity to create a basis for larval control initiatives in the country. METHODS Longitudinal surveys were conducted in randomly selected larval habitats over a period of fifteen months in Chikwawa district, southern Malawi. Biotic and abiotic parameters of the habitats were modelled to determine their effect on the occurrence and densities of anopheline larvae. RESULTS Seventy aquatic habitats were individually visited between 1-7 times over the study period. A total of 5,123 immature mosquitoes (3,359 anophelines, 1,497 culicines and 267 pupae) were collected. Anopheline and culicine larvae were observed in sympatry in aquatic habitats. Of the nine habitat types followed, dams, swamps, ponds, borehole runoffs and drainage channels were the five most productive habitat types for anopheline mosquitoes. Anopheline densities were higher in aquatic habitats with bare soil making up part of the surrounding land cover (p<0.01) and in aquatic habitats with culicine larvae (p<0.01) than in those surrounded by vegetation and not occupied by culicine larvae. Anopheline densities were significantly lower in highly turbid habitats than in clearer habitats (p<0.01). Presence of predators in the aquatic habitats significantly reduced the probability of anopheline larvae being present (p=0.04). CONCLUSIONS Anopheline larval habitats are widespread in the study area. Presence of bare soil, culicine larvae, predators and the level of turbidity of water are the main determinants of anopheline larval densities in aquatic habitats in Majete, Malawi. While the most productive aquatic habitats should be prioritised, for the most effective control of vectors in the area all available aquatic habitats should be targeted, even those that are not characterized by the identified predictors. Further research is needed to determine whether targeted LSM would be cost-effective when habitat characterisation is included in cost analyses and to establish what methods would make the characterisation of habitats easier.
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Deitz KC, Takken W, Slotman MA. The Genetic Architecture of Post-Zygotic Reproductive Isolation Between Anopheles coluzzii and An. quadriannulatus. Front Genet 2020; 11:925. [PMID: 33005168 PMCID: PMC7480394 DOI: 10.3389/fgene.2020.00925] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 07/24/2020] [Indexed: 11/15/2022] Open
Abstract
The Anopheles gambiae complex is comprised of eight morphologically indistinguishable species and has emerged as a model system for the study of speciation genetics due to the rapid radiation of its member species over the past two million years. Male hybrids between most An. gambiae complex species pairs are sterile, and some genotype combinations in hybrid males cause inviability. We investigated the genetic basis of hybrid male inviability and sterility between An. coluzzii and An. quadriannulatus by measuring segregation distortion and performing a QTL analysis of sterility in a backcross population. Hybrid males were inviable if they inherited the An. coluzzii X chromosome and were homozygous at one or more loci in 18.9 Mb region of chromosome 3. The An. coluzzii X chromosome has a disproportionately large effect on hybrid sterility when introgressed into an An. quadriannulatus genetic background. Additionally, an epistatic interaction between the An. coluzzii X and a 1.12 Mb, pericentric region of the An. quadriannulatus 3L chromosome arm has a statistically significant contribution to the hybrid sterility phenotype. This same epistatic interaction occurs when the An. coluzzii X is introgressed into the genetic background of An. arabiensis, the sister species of An. quadriannulatus, suggesting that this may represent one of the first Dobzhansky-Muller incompatibilities to evolve early in the radiation of the Anopheles gambiae species complex. We describe the additive effects of each sterility QTL, epistatic interactions between them, and genes within QTL with protein functions related to mating behavior, reproduction, spermatogenesis, and microtubule morphogenesis, whose divergence may contribute to post-zygotic reproductive isolation between An. coluzzii and An. quadriannulatus.
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Affiliation(s)
- Kevin C Deitz
- Department of Entomology, Texas A&M University, College Station, TX, United States
| | - Willem Takken
- Laboratory of Entomology, Wageningen University and Research, Wageningen, Netherlands
| | - Michel A Slotman
- Department of Entomology, Texas A&M University, College Station, TX, United States
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Gowelo S, McCann RS, Koenraadt CJM, Takken W, van den Berg H, Manda-Taylor L. Community factors affecting participation in larval source management for malaria control in Chikwawa District, Southern Malawi. Malar J 2020; 19:195. [PMID: 32487233 PMCID: PMC7265157 DOI: 10.1186/s12936-020-03268-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Accepted: 05/23/2020] [Indexed: 11/12/2022] Open
Abstract
Background To further reduce malaria, larval source management (LSM) is proposed as a complementary strategy to the existing strategies. LSM has potential to control insecticide resistant, outdoor biting and outdoor resting vectors. Concerns about costs and operational feasibility of implementation of LSM at large scale are among the reasons the strategy is not utilized in many African countries. Involving communities in LSM could increase intervention coverage, reduce costs of implementation and improve sustainability of operations. Community acceptance and participation in community-led LSM depends on a number of factors. These factors were explored under the Majete Malaria Project in Chikwawa district, southern Malawi. Methods Separate focus group discussions (FGDs) were conducted with members from the general community (n = 3); health animators (HAs) (n = 3); and LSM committee members (n = 3). In-depth interviews (IDIs) were conducted with community members. Framework analysis was employed to determine the factors contributing to community acceptance and participation in the locally-driven intervention. Results Nine FGDs and 24 IDIs were held, involving 87 members of the community. Widespread knowledge of malaria as a health problem, its mode of transmission, mosquito larval habitats and mosquito control was recorded. High awareness of an association between creation of larval habitats and malaria transmission was reported. Perception of LSM as a tool for malaria control was high. The use of a microbial larvicide as a form of LSM was perceived as both safe and effective. However, actual participation in LSM by the different interviewee groups varied. Labour-intensiveness and time requirements of the LSM activities, lack of financial incentives, and concern about health risks when wading in water bodies contributed to lower participation. Conclusion Community involvement in LSM increased local awareness of malaria as a health problem, its risk factors and control strategies. However, community participation varied among the respondent groups, with labour and time demands of the activities, and lack of incentives, contributing to reduced participation. Innovative tools that can reduce the labour and time demands could improve community participation in the activities. Further studies are required to investigate the forms and modes of delivery of incentives in operational community-driven LSM interventions.
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Affiliation(s)
- Steven Gowelo
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands. .,Training and Research Unit of Excellence, School of Public Health, College of Medicine, Blantyre, Malawi.
| | - Robert S McCann
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands.,Training and Research Unit of Excellence, School of Public Health, College of Medicine, Blantyre, Malawi.,Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, USA
| | | | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Henk van den Berg
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Lucinda Manda-Taylor
- Training and Research Unit of Excellence, School of Public Health, College of Medicine, Blantyre, Malawi.,Department of Health Systems and Policy, School of Public Health and Family Medicine, College of Medicine, Blantyre, Malawi
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Ibáñez-Justicia A, Koenraadt CJM, Stroo A, van Lammeren R, Takken W. Risk-Based and Adaptive Invasive Mosquito Surveillance at Lucky Bamboo and Used Tire Importers in the Netherlands. J Am Mosq Control Assoc 2020; 36:89-98. [PMID: 33647128 DOI: 10.2987/20-6914.1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The detection of Aedes albopictus in Lucky bamboo (Dracaena sanderiana) greenhouses and Ae. atropalpus at used tire importers illustrates that the Netherlands is exposed to the risk of introductions of invasive mosquito species (IMS). In this study we implemented a risk-based and adaptive surveillance (2010-16) in order to detect introductions and prevent potential proliferation of IMS at these locations. Results at Lucky bamboo greenhouses show that interceptions of Ae. albopictus occurred every year, with 2010 and 2012 being the years with most locations found positive for this species (n = 6), and 2015 the year with the highest percentage of positive samples (4.1%). Furthermore, our results demonstrate that Ae. japonicus can also be associated with the import of Lucky bamboo. At used tire companies, IMS were found at 12 locations. Invasive mosquito species identified were Ae. albopictus, Ae. atropalpus, Ae. aegypti, and Ae. japonicus, of which Ae. albopictus has been found every year since 2010. The proportion of samples containing IMS was significantly higher before application of a covenant between the used tire importers and the Dutch government in 2013 (12.96%) than in the successive 3 years (2014 [6.93%], 2015 [4.24%], 2016 [5.09%], 1-sided binomial test, P < 0.01). It is concluded that risk-based and adaptive surveillance is an effective methodology for detection of IMS, and that application of governmental management measures in combination with mosquito control has stabilized the situation.
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Affiliation(s)
- Adolfo Ibáñez-Justicia
- Centre for Monitoring of Vectors, Netherlands Food and Consumer Product Safety Authority, Geertjesweg 15, 6706 EA Wageningen, The Netherlands
| | - Constantianus J M Koenraadt
- Wageningen University & Research, Department of Plant Sciences, Laboratory of Entomology, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Arjan Stroo
- Centre for Monitoring of Vectors, Netherlands Food and Consumer Product Safety Authority, Geertjesweg 15, 6706 EA Wageningen, The Netherlands
| | - Ron van Lammeren
- Wageningen University & Research, Department of Environmental Sciences, Laboratory of Geo-information Science and Remote Sensing, Droevendaalsesteeg 4, 6708 PB Wageningen, The Netherlands
| | - Willem Takken
- Wageningen University & Research, Department of Plant Sciences, Laboratory of Entomology, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
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Gowelo S, Chirombo J, Spitzen J, Koenraadt CJM, Mzilahowa T, van den Berg H, Takken W, McCann R. Effects of larval exposure to sublethal doses of Bacillus thuringiensis var. israelensis on body size, oviposition and survival of adult Anopheles coluzzii mosquitoes. Parasit Vectors 2020; 13:259. [PMID: 32416733 PMCID: PMC7229702 DOI: 10.1186/s13071-020-04132-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 05/11/2020] [Indexed: 12/02/2022] Open
Abstract
Background Application of the larvicide Bacillus thuringiensis var. israelensis (Bti) is a viable complementary strategy for malaria control. Efficacy of Bti is dose-dependent. There is a knowledge gap on the effects of larval exposure to sublethal Bti doses on emerging adult mosquitoes. The present study examined the effect of larval exposure to sublethal doses of Bti on the survival, body size and oviposition rate in adult Anopheles coluzzii. Methods Third-instar An. coluzzii larvae were exposed to control and sublethal Bti concentrations at LC20, LC50 and LC70 for 48 h. Surviving larvae were reared to adults under standard colony conditions. Thirty randomly selected females from each treatment were placed in separate cages and allowed to blood feed. Twenty-five gravid females from the blood-feeding cages were randomly selected and transferred into new cages where they were provided with oviposition cups. Numbers of eggs laid in each cage and mortality of all adult mosquitoes were recorded daily. Wing lengths were measured of 570 mosquitoes as a proxy for body size. Results Exposure to LC70Bti doses for 48 h as third-instar larvae reduced longevity of adult An. coluzzii mosquitoes. Time to death was 2.58 times shorter in females exposed to LC70Bti when compared to the control females. Estimated mortality hazard rates were also higher in females exposed to the LC50 and LC20 treatments, but these differences were not statistically significant. The females exposed to LC70 concentrations had 12% longer wings than the control group (P < 0.01). No differences in oviposition rate of the gravid females were observed between the treatments. Conclusions Exposure of An. coluzzii larvae to sublethal Bti doses reduces longevity of resultant adults and is associated with larger adult size and unclear effect on oviposition. These findings suggest that anopheline larval exposure to sublethal Bti doses, though not recommended, could reduce vectorial capacity for malaria vector populations by increasing mortality of resultant adults.![]()
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Affiliation(s)
- Steven Gowelo
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands. .,Training and Research Unit of Excellence, School of Public Health, College of Medicine, Blantyre, Malawi.
| | - James Chirombo
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi
| | - Jeroen Spitzen
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | | | | | - Henk van den Berg
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Robert McCann
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands.,Training and Research Unit of Excellence, School of Public Health, College of Medicine, Blantyre, Malawi.,Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, USA
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26
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Mwingira VS, Spitzen J, Mboera LEG, Torres-Estrada JL, Takken W. The Influence of Larval Stage and Density on Oviposition Site-Selection Behavior of the Afrotropical Malaria Mosquito Anopheles coluzzii (Diptera: Culicidae). J Med Entomol 2020; 57:657-666. [PMID: 31630193 PMCID: PMC7197694 DOI: 10.1093/jme/tjz172] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Indexed: 05/26/2023]
Abstract
In the selection of oviposition sites female mosquitoes use various cues to assess site quality to optimize survival of progeny. The presence of conspecific larvae influences this process. Interactive effects of oviposition site selection were studied in the malaria mosquito Anopheles coluzzii Coetzee & Wilkerson in dual- and no-choice assays, by exposing single gravid mosquitoes to oviposition cups containing 1) larvae of different developmental stages, 2) larvae-conditioned water (LCW), and 3) cups where visual cues of conspecific larvae were absent. Early-stage conspecific larvae had a positive effect on the oviposition response. By contrast, late stages of conspecific larvae had a negative effect. Oviposition choice was dependent on larval density. Moreover, in oviposition cups where larvae were hidden from view, late-stage larvae had a significant negative effect on oviposition suggesting the involvement of olfactory cues. LCW had no effect on oviposition response, indicating involvement of chemicals produced by larvae in vivo. It is concluded that the presence of larvae in a breeding site affects the oviposition response depending on the development stage of the larvae. These responses appear to be mediated by olfactory cues emitted by the larval habitat containing live larvae, resulting in the enhanced reproductive fitness of the females.
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Affiliation(s)
| | - Jeroen Spitzen
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Leonard E G Mboera
- National Institute for Medical Research, Tanga, Tanzania
- Southern African Centre for Infectious Disease Surveillance, Chuo Kikuu, Morogoro, Tanzania
| | - José L Torres-Estrada
- Centro de Investigación de Paludismo, Instituto Nacional de Salud Pública (INSP), Tapachula, Chiapas, México
| | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
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27
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Ibáñez-Justicia A, Alcaraz-Hernández JD, van Lammeren R, Koenraadt CJM, Bergsma A, Delucchi L, Rizzoli A, Takken W. Habitat suitability modelling to assess the introductions of Aedes albopictus (Diptera: Culicidae) in the Netherlands. Parasit Vectors 2020; 13:217. [PMID: 32336286 PMCID: PMC7184689 DOI: 10.1186/s13071-020-04077-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Accepted: 04/10/2020] [Indexed: 11/24/2022] Open
Abstract
Background In the Netherlands, Aedes albopictus has been found each year since 2010 during routine exotic mosquito species surveillance at companies that import used tires. We developed habitat suitability models to investigate the potential risk of establishment and spread of this invasive species at these locations. Methods We used two methodologies: first, a species distribution model based on the maximum entropy modelling approach (MaxEnt) taking into consideration updated occurrence data of the species in Europe, and secondly, a spatial logic conditional model based on the temperature requirements of the species and using land surface temperature data (LST model). Results Suitability assessment obtained with the MaxEnt model at European level accurately reflect the current distribution of the species and these results also depict moderately low values in parts of the Netherlands, Belgium, Denmark, the British islands and southern parts of Scandinavia. Winter temperature was the variable that contributed most to the performance of the model (47.3%). The results of the LST model showed that: (i) coastal areas are suitable for overwintering of eggs; (ii) large areas in the northern part of the country have a low suitability for adult survival; and (iii) the entire country is suitable for successful completion of the life-cycle if the species is introduced after the winter months. Results of the LST model revealed that temperatures in 2012 and 2014 did not limit the overwintering of eggs or survival of adults at the locations where the species was found. By contrast, for the years 2010, 2011 and 2013, overwintering of eggs at these locations is considered unlikely. Conclusions Results using two modelling methodologies show differences in predicted habitat suitability values. Based on the results of both models, the climatic conditions could hamper the successful overwintering of eggs of Ae. albopictus and their survival as adults in many areas of the country. However, during warm years with mild winters, many areas of the Netherlands offer climatic conditions suitable for developing populations. Regular updates of the models, using updated occurrence and climatic data, are recommended to study the areas at risk.![]()
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Affiliation(s)
- Adolfo Ibáñez-Justicia
- Centre for Monitoring of Vectors (CMV), Netherlands Food and Consumer Product Safety Authority (NVWA), Wageningen, The Netherlands.
| | | | - Ron van Lammeren
- Laboratory of Geo-information Science and Remote Sensing, Wageningen University & Research, Wageningen, The Netherlands
| | | | - Aldo Bergsma
- Laboratory of Geo-information Science and Remote Sensing, Wageningen University & Research, Wageningen, The Netherlands
| | - Luca Delucchi
- Research and Innovation Centre, Fondazione Edmund Mach, San Michele all'Adige, Italy
| | - Annapaola Rizzoli
- Research and Innovation Centre, Fondazione Edmund Mach, San Michele all'Adige, Italy
| | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
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Athrey G, Popkin-Hall Z, Cosme LV, Takken W, Slotman MA. Species and sex-specific chemosensory gene expression in Anopheles coluzzii and An. quadriannulatus antennae. Parasit Vectors 2020; 13:212. [PMID: 32321556 PMCID: PMC7178735 DOI: 10.1186/s13071-020-04085-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Accepted: 04/15/2020] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Olfactory cues drive mosquito behaviors such as host-seeking, locating sugar sources and oviposition. These behaviors can vary between sexes and closely related species. For example, the malaria vector Anopheles coluzzii is highly anthropophilic, whereas An. quadriannulatus is not. These behavioral differences may be reflected in chemosensory gene expression. METHODS The expression of chemosensory genes in the antennae of both sexes of An. coluzzii and An. quadriannulatus was compared using RNA-seq. The sex-biased expression of several genes in An. coluzzii was also compared using qPCR. RESULTS The chemosensory expression is mostly similar in the male antennae of An. coluzzii and An. quadriannulatus, with only a few modest differences in expression. A handful of chemosensory genes are male-biased in both species; the highly expressed gustatory receptor AgGr33, odorant binding proteins AgObp25, AgObp26 and possibly AgObp10. Although the chemosensory gene repertoire is mostly shared between the sexes, several highly female-biased AgOrs, AgIrs, and one AgObp were identified, including several whose expression is biased towards the anthropophilic An. coluzzii. Additionally, the expression of several chemosensory genes is biased towards An. coluzzii in both sexes. CONCLUSIONS Chemosensory gene expression is broadly similar between species and sexes, but several sex- biased/specific genes were identified. These may modulate sex- and species-specific behaviors. Although the male behavior of these species remains poorly studied, the identification of sex- and species-specific chemosensory genes may provide fertile ground for future work.
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Affiliation(s)
- Giridhar Athrey
- Department of Poultry Science, Texas A&M University, College Station, TX USA
| | | | - Luciano Veiga Cosme
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT USA
| | - Willem Takken
- Laboratory of Entomology, Wageningen University and Research, Wageningen, The Netherlands
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Schoelitsz B, Mwingira V, Mboera LEG, Beijleveld H, Koenraadt CJM, Spitzen J, van Loon JJA, Takken W. Chemical Mediation of Oviposition by Anopheles Mosquitoes: a Push-Pull System Driven by Volatiles Associated with Larval Stages. J Chem Ecol 2020; 46:397-409. [PMID: 32240482 PMCID: PMC7205850 DOI: 10.1007/s10886-020-01175-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2020] [Revised: 03/15/2020] [Accepted: 03/19/2020] [Indexed: 11/05/2022]
Abstract
The oviposition behavior of mosquitoes is mediated by chemical cues. In the malaria mosquito Anopheles gambiae, conspecific larvae produce infochemicals that affect this behavior. Emanations from first instar larvae proved strongly attractive to gravid females, while those from fourth instars caused oviposition deterrence, suggesting that larval developmental stage affected the oviposition choice of the female mosquito. We examined the nature of these chemicals by headspace collection of emanations of water in which larvae of different stages were developing. Four chemicals with putative effects on oviposition behavior were identified: dimethyldisulfide (DMDS) and dimethyltrisulfide (DMTS) were identified in emanations from water containing fourth instars; nonane and 2,4-pentanedione (2,4-PD) were identified in emanations from water containing both first and fourth instars. Dual-choice oviposition studies with these compounds were done in the laboratory and in semi-field experiments in Tanzania. In the laboratory, DMDS and DMTS were associated with oviposition-deterrent effects, while results with nonane and 2,4-PD were inconclusive. In further studies DMDS and DMTS evoked egg retention, while with nonane and 2,4-PD 88% and 100% of female mosquitoes, respectively, laid eggs. In dual-choice semi-field trials DMDS and DMTS caused oviposition deterrence, while nonane and 2,4-PD evoked attraction, inducing females to lay more eggs in bowls containing these compounds compared to the controls. We conclude that oviposition of An. gambiae is mediated by these four infochemicals associated with conspecific larvae, eliciting either attraction or deterrence. High levels of egg retention occurred when females were exposed to chemicals associated with fourth instar larvae.
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Affiliation(s)
- Bruce Schoelitsz
- Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA,, Wageningen, The Netherlands.,HAS University of Applied Sciences, Onderwijsboulevard 221, 5223 DE,, 's-Hertogenbosch, The Netherlands
| | - Victor Mwingira
- Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA,, Wageningen, The Netherlands.,National Institute for Medical Research, Amani Research Centre, P.O. Box 81, Muheza, Tanzania
| | - Leonard E G Mboera
- SACIDS Foundation for One Health, Sokoine University of Agriculture, P.O. Box 3297, Morogoro, Chuo Kikuu, Tanzania
| | - Hans Beijleveld
- Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA,, Wageningen, The Netherlands.,Environmental Technology, Wageningen University & Research, Bornsesteeg 59B, 6708 PD, Wageningen, The Netherlands
| | - Constantianus J M Koenraadt
- Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA,, Wageningen, The Netherlands
| | - Jeroen Spitzen
- Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA,, Wageningen, The Netherlands
| | - Joop J A van Loon
- Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA,, Wageningen, The Netherlands
| | - Willem Takken
- Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA,, Wageningen, The Netherlands.
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30
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Bakker JW, Loy DE, Takken W, Hahn BH, Verhulst NO. Attraction of mosquitoes to primate odours and implications for zoonotic Plasmodium transmission. Med Vet Entomol 2020; 34:17-26. [PMID: 31420992 PMCID: PMC7002228 DOI: 10.1111/mve.12402] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 04/18/2019] [Accepted: 07/24/2019] [Indexed: 05/05/2023]
Abstract
Vector-borne diseases often originate from wildlife and can spill over into the human population. One of the most important determinants of vector-borne disease transmission is the host preference of mosquitoes. Mosquitoes with a specialised host preference are guided by body odours to find their hosts in addition to carbon dioxide. Little is known about the role of mosquito host preference in the spillover of pathogenic agents from humans towards animals and vice versa. In the Republic of Congo, the attraction of mosquitoes to primate host odours was determined, as well as their possible role as malaria vectors, using odour-baited traps mimicking the potential hosts of mosquitoes. Most of the mosquito species caught showed a generalistic host preference. Anopheles obscurus was the most abundant Anopheles mosquito, with a generalistic host preference observed from the olfactory response and the detection of various Plasmodium parasites. Interestingly, Culex decens showed a much higher attraction towards chimpanzee odours than to human or cow odours. Human Plasmodium parasites were observed in both human and chimpanzee blood, although not in the Anopheles mosquitoes that were collected. Understanding the role of mosquito host preference for cross-species parasite transmission provides information that will help to determine the risk of spillover of vector-borne diseases.
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Affiliation(s)
- J. W. Bakker
- Laboratory of EntomologyWageningen University & ResearchWageningenThe Netherlands
| | - D. E. Loy
- Departments of Medicine and Microbiology, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaPAU.S.A.
| | - W. Takken
- Laboratory of EntomologyWageningen University & ResearchWageningenThe Netherlands
| | - B. H. Hahn
- Departments of Medicine and Microbiology, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaPAU.S.A.
| | - N. O. Verhulst
- Laboratory of EntomologyWageningen University & ResearchWageningenThe Netherlands
- National Centre for Vector Entomology, Institute of Parasitology, Vetsuisse FacultyUniversity of ZurichZurichSwitzerland
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Krawczyk AI, van Duijvendijk GLA, Swart A, Heylen D, Jaarsma RI, Jacobs FHH, Fonville M, Sprong H, Takken W. Effect of rodent density on tick and tick-borne pathogen populations: consequences for infectious disease risk. Parasit Vectors 2020; 13:34. [PMID: 31959217 PMCID: PMC6971888 DOI: 10.1186/s13071-020-3902-0] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Accepted: 01/08/2020] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Rodents are considered to contribute strongly to the risk of tick-borne diseases by feeding Ixodes ricinus larvae and by acting as amplifying hosts for pathogens. Here, we tested to what extent these two processes depend on rodent density, and for which pathogen species rodents synergistically contribute to the local disease risk, i.e. the density of infected nymphs (DIN). METHODS In a natural woodland, we manipulated rodent densities in plots of 2500 m2 by either supplementing a critical food source (acorns) or by removing rodents during two years. Untreated plots were used as controls. Collected nymphs and rodent ear biopsies were tested for the presence of seven tick-borne microorganisms. Linear models were used to capture associations between rodents, nymphs, and pathogens. RESULTS Investigation of data from all plots, irrespective of the treatment, revealed a strong positive association between rodent density and nymphal density, nymphal infection prevalence (NIP) with Borrelia afzelii and Neoehrlichia mikurensis, and hence DIN's of these pathogens in the following year. The NIP, but not the DIN, of the bird-associated Borrelia garinii, decreased with increasing rodent density. The NIPs of Borrelia miyamotoi and Rickettsia helvetica were independent of rodent density, and increasing rodent density moderately increased the DINs. In addition, NIPs of Babesia microti and Spiroplasma ixodetis decreased with increasing rodent density, which had a non-linear association with DINs of these microorganisms. CONCLUSIONS A positive density dependence for all rodent- and tick-associated tick-borne pathogens was found, despite the observation that some of them decreased in prevalence. The effects on the DINs were variable among microorganisms, more than likely due to contrasts in their biology (including transmission modes, host specificity and transmission efficiency). The strongest associations were found in rodent-associated pathogens that most heavily rely on horizontal transmission. Our results draw attention to the importance of considering transmission mode of a pathogen while developing preventative measures to successfully reduce the burden of disease.
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Affiliation(s)
- Aleksandra I Krawczyk
- Laboratory of Entomology, Wageningen University and Research Centre, Wageningen, The Netherlands. .,Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Antonie van Leeuwenhoeklaan 9, 3721 MA, Bilthoven, The Netherlands.
| | | | - Arno Swart
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Antonie van Leeuwenhoeklaan 9, 3721 MA, Bilthoven, The Netherlands
| | - Dieter Heylen
- Interuniversity Institute for Biostatistics and statistical Bioinformatics, Hasselt University, Diepenbeek, Belgium.,Department of Ecology and Evolutionary Biology, Princeton University, 106A Guyot Ln, Princeton, NJ, 08544, USA
| | - Ryanne I Jaarsma
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Antonie van Leeuwenhoeklaan 9, 3721 MA, Bilthoven, The Netherlands
| | - Frans H H Jacobs
- Laboratory of Entomology, Wageningen University and Research Centre, Wageningen, The Netherlands
| | - Manoj Fonville
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Antonie van Leeuwenhoeklaan 9, 3721 MA, Bilthoven, The Netherlands
| | - Hein Sprong
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Antonie van Leeuwenhoeklaan 9, 3721 MA, Bilthoven, The Netherlands.
| | - Willem Takken
- Laboratory of Entomology, Wageningen University and Research Centre, Wageningen, The Netherlands
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Wilson AL, Courtenay O, Kelly-Hope LA, Scott TW, Takken W, Torr SJ, Lindsay SW. The importance of vector control for the control and elimination of vector-borne diseases. PLoS Negl Trop Dis 2020; 14:e0007831. [PMID: 31945061 PMCID: PMC6964823 DOI: 10.1371/journal.pntd.0007831] [Citation(s) in RCA: 251] [Impact Index Per Article: 62.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Vector-borne diseases (VBDs) such as malaria, dengue, and leishmaniasis exert a huge burden of morbidity and mortality worldwide, particularly affecting the poorest of the poor. The principal method by which these diseases are controlled is through vector control, which has a long and distinguished history. Vector control, to a greater extent than drugs or vaccines, has been responsible for shrinking the map of many VBDs. Here, we describe the history of vector control programmes worldwide from the late 1800s to date. Pre 1940, vector control relied on a thorough understanding of vector ecology and epidemiology, and implementation of environmental management tailored to the ecology and behaviour of local vector species. This complex understanding was replaced by a simplified dependency on a handful of insecticide-based tools, particularly for malaria control, without an adequate understanding of entomology and epidemiology and without proper monitoring and evaluation. With the rising threat from insecticide-resistant vectors, global environmental change, and the need to incorporate more vector control interventions to eliminate these diseases, we advocate for continued investment in evidence-based vector control. There is a need to return to vector control approaches based on a thorough knowledge of the determinants of pathogen transmission, which utilise a range of insecticide and non-insecticide-based approaches in a locally tailored manner for more effective and sustainable vector control.
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Affiliation(s)
- Anne L. Wilson
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Orin Courtenay
- Zeeman Institute and School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | - Louise A. Kelly-Hope
- Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Thomas W. Scott
- Department of Entomology and Nematology, University of California Davis, Davis, California, United States of America
| | - Willem Takken
- Department of Plant Sciences, Wageningen University and Research, Wageningen, the Netherlands
| | - Steve J. Torr
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Steve W. Lindsay
- Department of Biosciences, Durham University, Durham, United Kingdom
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Möhlmann TWR, Bekendam AM, van Kemenade I, Wennergren U, Favia G, Takken W, Koenraadt CJM. Latitudinal diversity of biting midge species within the Obsoletus group across three habitats in Europe. Med Vet Entomol 2019; 33:420-426. [PMID: 31033029 PMCID: PMC6849825 DOI: 10.1111/mve.12379] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Revised: 03/11/2019] [Accepted: 03/21/2019] [Indexed: 05/22/2023]
Abstract
Culicoides species from the Obsoletus group are important vectors of bluetongue and Schmallenberg virus. This group consists of several species that cannot easily be identified using morphological characteristics. Therefore, limited information is available about their distribution and habitat preferences. In this study, we aimed to elucidate the species composition of the Obsoletus group in three habitat types at climatically different latitudes across Europe. Traps were placed in three habitat types in three countries at different latitudes. After DNA extraction, biting midges were identified using PCR and gel electrophoresis. Extraction of DNA using Chelex proved to be a cost and time efficient method for species identification. A latitudinal effect on the relative abundance of species from the Obsoletus group was found. Species composition was unique for most country-habitat combinations. The majority of biting midges were either C. obsoletus s.s. or C. scoticus, and both species were found at all latitudes and habitats. Their wide distribution and their high abundance at livestock farms make these species likely candidates for rapid farm-to-farm transmission of pathogens throughout Europe. Our results emphasize the need to differentiate Obsoletus group species to better understand their ecology and contribution to pathogen transmission.
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Affiliation(s)
- T. W. R. Möhlmann
- Laboratory of EntomologyWageningen University and ResearchWageningenThe Netherlands
- IFM Theory and ModellingLinköping UniversityLinköpingSweden
| | - A. M. Bekendam
- Laboratory of EntomologyWageningen University and ResearchWageningenThe Netherlands
| | - I. van Kemenade
- Laboratory of EntomologyWageningen University and ResearchWageningenThe Netherlands
| | - U. Wennergren
- IFM Theory and ModellingLinköping UniversityLinköpingSweden
| | - G. Favia
- School of Biosciences and Veterinary MedicineUniversity of CamerinoCamerinoItaly
| | - W. Takken
- Laboratory of EntomologyWageningen University and ResearchWageningenThe Netherlands
| | - C. J. M. Koenraadt
- Laboratory of EntomologyWageningen University and ResearchWageningenThe Netherlands
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Kaunda-Khangamwa BN, van den Berg H, McCann RS, Kabaghe A, Takken W, Phiri K, van Vugt M, Manda-Taylor L. The role of health animators in malaria control: a qualitative study of the health animator (HA) approach within the Majete malaria project (MMP) in Chikwawa District, Malawi. BMC Health Serv Res 2019; 19:478. [PMID: 31299974 PMCID: PMC6624973 DOI: 10.1186/s12913-019-4320-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 07/02/2019] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Malaria continues to place a high burden on communities due to challenges reaching intervention target levels in Chikwawa District, Malawi. The Hunger Project Malawi is using a health animator approach (HA) to address gaps in malaria control coverage. We explored the influence of community-based volunteers known as health animators (HAs) in malaria control. We assessed the impact of HAs on knowledge, attitudes, and practices towards malaria interventions. METHODS This paper draws on the qualitative data collected to explore the roles of communities, HAs and formal health workers attending and not attending malaria workshops for malaria control. Purposive sampling was used to select 78 respondents. We conducted 10 separate focus group discussions (FGDs)-(n = 6) with community members and (n = 4) key informants. Nine in-depth interviews (IDIs) were held with HAs and Health Surveillance Assistants (HSAs) in three focal areas near Majete Wildlife Reserve. Nvivo 11 was used for coding and analysis. We employed the framework analysis and social capital theory to determine how the intervention influenced health and social outcomes. RESULTS Using education, feedback sessions and advocacy in malaria workshop had mixed outcomes. There was a high awareness of community participation and comprehensive knowledge of the HA approach as key to malaria control. HAs were identified as playing a complementary role in malaria intervention. Community members' attitudes towards advocacy for better health services were poor. Attendance in malaria workshops was sporadic towards the final year of the intervention. Respondents mentioned positive attitudes and practices on net usage for prevention and prompt health-seeking behaviours. CONCLUSION The HA approach is a useful strategy for complementing malaria prevention strategies in rural communities and improving practices for health-seeking behaviour. Various factors influence HAs' motivation, retention, community engagement, and programme sustainability. However, little is known about how these factors interact to influence volunteers' motivation, community participation and sustainability over time. More research is needed to explore the acceptability of an HA approach and the impact on malaria control in other rural communities in Malawi.
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Affiliation(s)
- Blessings N. Kaunda-Khangamwa
- The School of Public Health and Family Medicine, University of Malawi, College of Medicine, Blantyre, Malawi
- The Malaria Alert Centre, University of Malawi, College of Medicine, Blantyre, Malawi
- The University of Witwatersrand, School of Public Health, Johannesburg, South Africa
| | - Henk van den Berg
- Amsterdam UMC, location Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - Robert S. McCann
- Wageningen University and Research Centre, Wageningen, The Netherlands
- Training and Research Unit of Excellence, University of Malawi, College of Medicine, Blantyre, Malawi
| | - Alinune Kabaghe
- The School of Public Health and Family Medicine, University of Malawi, College of Medicine, Blantyre, Malawi
- Training and Research Unit of Excellence, University of Malawi, College of Medicine, Blantyre, Malawi
| | - Willem Takken
- Wageningen University and Research Centre, Wageningen, The Netherlands
| | - Kamija Phiri
- The School of Public Health and Family Medicine, University of Malawi, College of Medicine, Blantyre, Malawi
- Training and Research Unit of Excellence, University of Malawi, College of Medicine, Blantyre, Malawi
| | - Michele van Vugt
- Amsterdam UMC, location Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - Lucinda Manda-Taylor
- The School of Public Health and Family Medicine, University of Malawi, College of Medicine, Blantyre, Malawi
- Training and Research Unit of Excellence, University of Malawi, College of Medicine, Blantyre, Malawi
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McCann RS, van den Berg H, Takken W, Chetwynd AG, Giorgi E, Terlouw DJ, Diggle PJ. Reducing contamination risk in cluster-randomized infectious disease-intervention trials. Int J Epidemiol 2019; 47:2015-2024. [PMID: 30376050 DOI: 10.1093/ije/dyy213] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/13/2018] [Indexed: 11/13/2022] Open
Abstract
Background Infectious disease interventions are increasingly tested using cluster-randomized trials (CRTs). These trial settings tend to involve a set of sampling units, such as villages, whose geographic arrangement may present a contamination risk in treatment exposure. The most widely used approach for reducing contamination in these settings is the so-called fried-egg design, which excludes the outer portion of all available clusters from the primary trial analysis. However, the fried-egg design ignores potential intra-cluster spatial heterogeneity and makes the outcome measure inherently less precise. Whereas the fried-egg design may be appropriate in specific settings, alternative methods to optimize the design of CRTs in other settings are lacking. Methods We present a novel approach for CRT design that either fully includes or fully excludes available clusters in a defined study region, recognizing the potential for intra-cluster spatial heterogeneity. The approach includes an algorithm that allows investigators to identify the maximum number of clusters that could be included for a defined study region and maintain randomness in both the selection of included clusters and the allocation of clusters to either the treatment group or control group. The approach was applied to the design of a CRT testing the effectiveness of malaria vector-control interventions in southern Malawi. Conclusions Those planning CRTs to evaluate interventions should consider the approach presented here during trial design. The approach provides a novel framework for reducing the risk of contamination among the CRT randomization units in settings where investigators determine the reduction of contamination risk as a high priority and where intra-cluster spatial heterogeneity is likely. By maintaining randomness in the allocation of clusters to either the treatment group or control group, the approach also permits a randomization-valid test of the primary trial hypothesis.
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Affiliation(s)
- Robert S McCann
- Laboratory of Entomology, Wageningen University and Research, Wageningen, The Netherlands.,Department of Public Health, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Henk van den Berg
- Laboratory of Entomology, Wageningen University and Research, Wageningen, The Netherlands
| | - Willem Takken
- Laboratory of Entomology, Wageningen University and Research, Wageningen, The Netherlands
| | - Amanda G Chetwynd
- Department of Mathematics and Statistics, Lancaster University, Lancaster, United Kingdom
| | - Emanuele Giorgi
- CHICAS, Lancaster Medical School, Lancaster University, Lancaster, United Kingdom
| | - Dianne J Terlouw
- Department of Public Health, College of Medicine, University of Malawi, Blantyre, Malawi.,Malawi-Liverpool Wellcome Trust Clinical Research Program, Blantyre, Malawi.,Clinical Sciences Department, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Peter J Diggle
- CHICAS, Lancaster Medical School, Lancaster University, Lancaster, United Kingdom
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Hartemink N, van Vliet A, Sprong H, Jacobs F, Garcia-Martí I, Zurita-Milla R, Takken W. Temporal-Spatial Variation in Questing Tick Activity in the Netherlands: The Effect of Climatic and Habitat Factors. Vector Borne Zoonotic Dis 2019; 19:494-505. [PMID: 30810501 DOI: 10.1089/vbz.2018.2369] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Longitudinal studies are fundamental in the assessment of the effect of environmental factors on tick population dynamics. In this study, we use data from a 10-year study in 11 different locations in the Netherlands to gauge the effects of climatic and habitat factors on the temporal and spatial variation in questing tick activity. Marked differences in the total number of ticks were found between locations and between years. We investigated which climatic and habitat factors might explain this variation. No effects of climatic factors on the total number of ticks per year were observed, but we found a clear effect of temperature on the onset of tick activity. In addition, we found positive associations between (1) humus layer thickness and densities of all three stages, (2) moss and blackberry abundance and larval densities, and (3) blueberry abundance and densities of larva and nymphs. We conclude that climatic variables do not have a straightforward association with tick density in the Netherlands, but that winter and spring temperatures influence the onset of tick activity. Habitats with apparently similar vegetation types can still differ in tick population densities, indicating that local composition of vegetation and especially of wildlife is likely to contribute considerably to the spatial variation in tick densities.
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Affiliation(s)
- Nienke Hartemink
- 1 Biometris, Wageningen University and Research Centre, Wageningen, the Netherlands.,2 Laboratory of Entomology, Wageningen University and Research Centre, Wageningen, the Netherlands
| | - Arnold van Vliet
- 3 Environmental Systems Analysis Group, Wageningen University and Research Centre, Wageningen, the Netherlands
| | - Hein Sprong
- 2 Laboratory of Entomology, Wageningen University and Research Centre, Wageningen, the Netherlands.,4 Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, the Netherlands
| | - Frans Jacobs
- 2 Laboratory of Entomology, Wageningen University and Research Centre, Wageningen, the Netherlands.,5 Centre for Vector Surveillance, Netherlands Food and Consumer Product Safety Authority, Wageningen, the Netherlands
| | - Irene Garcia-Martí
- 6 Royal Netherlands Meteorological Institute, De Bilt, the Netherlands.,7 Faculty of Geo-Information Science and Earth Observation, University of Twente, Enschede, the Netherlands
| | - Raul Zurita-Milla
- 7 Faculty of Geo-Information Science and Earth Observation, University of Twente, Enschede, the Netherlands
| | - Willem Takken
- 2 Laboratory of Entomology, Wageningen University and Research Centre, Wageningen, the Netherlands
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Mburu MM, Zembere K, Hiscox A, Banda J, Phiri KS, van den Berg H, Mzilahowa T, Takken W, McCann RS. Assessment of the Suna trap for sampling mosquitoes indoors and outdoors. Malar J 2019; 18:51. [PMID: 30795766 PMCID: PMC6387520 DOI: 10.1186/s12936-019-2680-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Accepted: 02/14/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Entomological monitoring is important for public health because it provides data on the distribution, abundance and host-seeking behaviour of disease vectors. Various methods for sampling mosquitoes exist, most of which are biased towards, or specifically target, certain portions of a mosquito population. This study assessed the Suna trap, an odour-baited trap for sampling host-seeking mosquitoes both indoors and outdoors. METHODS Two separate field experiments were conducted in villages in southern Malawi. The efficiency of the Suna trap in sampling mosquitoes was compared to that of the human landing catch (HLC) indoors and outdoors and the Centers for Disease, Control and Prevention Light Trap (CDC-LT) indoors. Potential competition between two Suna traps during simultaneous use of the traps indoors and outdoors was assessed by comparing mosquito catch sizes across three treatments: one trap indoors only; one trap outdoors only; and one trap indoors and one trap outdoors used simultaneously at the same house. RESULTS The efficiency of the Suna trap in sampling female anophelines was similar to that of HLC indoors (P = 0.271) and HLC outdoors (P = 0.125), but lower than that of CDC-LT indoors (P = 0.001). Anopheline catch sizes in the Suna trap used alone indoors were similar to indoor Suna trap catch sizes when another Suna trap was simultaneously present outdoors (P = 0.891). Similarly, catch sizes of female anophelines with the Suna trap outdoors were similar to those that were caught outdoors when another Suna trap was simultaneously present indoors (P = 0.731). CONCLUSIONS The efficiency of the Suna trap in sampling mosquitoes was equivalent to that of the HLC. Whereas the CDC-LT was more efficient in collecting female anophelines indoors, the use of this trap outdoors is limited given the requirement of setting it next to an occupied bed net. As demonstrated in this research, outdoor collections are also essential because they provide data on the relative contribution of outdoor biting to malaria transmission. Therefore, the Suna trap could serve as an alternative to the HLC and the CDC-LT, because it does not require the use of humans as natural baits, allows standardised sampling conditions across sampling points, and can be used outdoors. Furthermore, using two Suna traps simultaneously indoors and outdoors does not interfere with the sampling efficiency of either trap, which would save a considerable amount of time, energy, and resources compared to setting the traps indoors and then outdoors in two consecutive nights.
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Affiliation(s)
- Monicah M Mburu
- College of Medicine, University of Malawi, Blantyre, Malawi. .,Laboratory of Entomology, Wageningen University and Research, Wageningen, The Netherlands.
| | | | - Alexandra Hiscox
- Laboratory of Entomology, Wageningen University and Research, Wageningen, The Netherlands
| | - Jomo Banda
- College of Medicine, University of Malawi, Blantyre, Malawi.,MAC Communicable Diseases Action Centre, Blantyre, Malawi
| | - Kamija S Phiri
- College of Medicine, University of Malawi, Blantyre, Malawi
| | - Henk van den Berg
- Laboratory of Entomology, Wageningen University and Research, Wageningen, The Netherlands
| | - Themba Mzilahowa
- College of Medicine, University of Malawi, Blantyre, Malawi.,MAC Communicable Diseases Action Centre, Blantyre, Malawi
| | - Willem Takken
- Laboratory of Entomology, Wageningen University and Research, Wageningen, The Netherlands
| | - Robert S McCann
- College of Medicine, University of Malawi, Blantyre, Malawi.,Laboratory of Entomology, Wageningen University and Research, Wageningen, The Netherlands
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de Boer JG, Busula AO, Ten Berge J, van Dijk TS, Takken W. Does artemether-lumefantrine administration affect mosquito olfactory behaviour and fitness? Malar J 2019; 18:28. [PMID: 30691446 PMCID: PMC6350316 DOI: 10.1186/s12936-019-2646-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 01/11/2019] [Indexed: 11/24/2022] Open
Abstract
Background Artemisinin-based combination therapy (ACT) is the recommended treatment against uncomplicated Plasmodium falciparum infections, and ACT is widely used. It has been shown that gametocytes may be present after ACT and transmission to mosquitoes is still possible. Artemether–lumefantrine (AL) is a broadly used artemisinin-based combination medicine. Here, it is tested whether AL influences behaviour and fitness of Anopheles mosquitoes, which are the main vectors of P. falciparum. Results Dual-choice olfactometer and screenhouse experiments showed that skin odour of healthy human individuals obtained before, during and after AL-administration was equally attractive to Anopheles coluzzii and Anopheles gambiae sensu stricto, apart from a small (but significant) increase in mosquito response to skin odour collected 3 weeks after AL-administration. Anopheles coluzzii females fed on parasite-free blood supplemented with AL or on control-blood had similar survival, time until oviposition and number of eggs produced. Conclusions Based on the results, AL does not appear to influence malaria transmission through modification of vector mosquito olfactory behaviour or fitness. Extending these studies to Plasmodium-infected individuals and malaria mosquitoes with parasites are needed to further support this conclusion. Electronic supplementary material The online version of this article (10.1186/s12936-019-2646-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jetske G de Boer
- Laboratory of Entomology, Wageningen University & Research, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands. .,Netherlands Institute of Ecology, Droevendaalsesteeg 10, 6708 PB, Wageningen, The Netherlands.
| | - Annette O Busula
- Laboratory of Entomology, Wageningen University & Research, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands.,International Centre of Insect Physiology and Ecology, P.O BOX 30772-00100 GPO, Nairobi, Kenya.,Kaimosi Friends University College, P.O BOX 385-50309, Kaimosi, Kenya
| | - Jet Ten Berge
- Laboratory of Entomology, Wageningen University & Research, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands
| | - Tessa S van Dijk
- Laboratory of Entomology, Wageningen University & Research, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands
| | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands
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Deitz KC, Takken W, Slotman MA. The Effect of Hybridization on Dosage Compensation in Member Species of the Anopheles gambiae Species Complex. Genome Biol Evol 2018; 10:1663-1672. [PMID: 29860336 PMCID: PMC6037052 DOI: 10.1093/gbe/evy108] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/30/2018] [Indexed: 12/17/2022] Open
Abstract
Dosage compensation has evolved in concert with Y-chromosome degeneration in many taxa that exhibit heterogametic sex chromosomes. Dosage compensation overcomes the biological challenge of a “half dose” of X chromosome gene transcripts in the heterogametic sex. The need to equalize gene expression of a hemizygous X with that of autosomes arises from the fact that the X chromosomes retain hundreds of functional genes that are actively transcribed in both sexes and interact with genes expressed on the autosomes. Sex determination and heterogametic sex chromosomes have evolved multiple times in Diptera, and in each case the genetic control of dosage compensation is tightly linked to sex determination. In the Anopheles gambiae species complex (Culicidae), maleness is conferred by the Y-chromosome gene Yob, which despite its conserved role between species is polymorphic in its copy number between them. Previous work demonstrated that male An. gambiae s.s. males exhibit complete dosage compensation in pupal and adult stages. In the present study, we have extended this analysis to three sister species in the An. gambiae complex: An. coluzzii, An. arabiensis, and An. quadriannulatus. In addition, we analyzed dosage compensation in bi-directional F1 hybrids between these species to determine if hybridization results in the mis-regulation and disruption of dosage compensation. Our results confirm that dosage compensation operates in the An. gambiae species complex through the hypertranscription of the male X chromosome. Additionally, dosage compensation in hybrid males does not differ from parental males, indicating that hybridization does not result in the mis-regulation of dosage compensation.
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Affiliation(s)
- Kevin C Deitz
- Department of Entomology, Texas A&M University.,Department of Ecology and Evolutionary Biology and The Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ
| | - Willem Takken
- Laboratory of Entomology, Department of Plant Sciences, Wageningen University, The Netherlands
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van den Berg H, van Vugt M, Kabaghe AN, Nkalapa M, Kaotcha R, Truwah Z, Malenga T, Kadama A, Banda S, Tizifa T, Gowelo S, Mburu MM, Phiri KS, Takken W, McCann RS. Community-based malaria control in southern Malawi: a description of experimental interventions of community workshops, house improvement and larval source management. Malar J 2018; 17:266. [PMID: 30012147 PMCID: PMC6048888 DOI: 10.1186/s12936-018-2415-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 07/10/2018] [Indexed: 12/22/2022] Open
Abstract
Background Increased engagement of communities has been emphasized in global plans for malaria control and elimination. Three interventions to reinforce and complement national malaria control recommendations were developed and applied within the context of a broad-based development initiative, targeting a rural population surrounding a wildlife reserve. The interventions, which were part of a 2-year research trial, and assigned to the village level, were implemented through trained local volunteers, or ‘health animators’, who educated the community and facilitated collective action. Results Community workshops on malaria were designed to increase uptake of national recommendations; a manual was developed, and training of health animators conducted, with educational content and analytical tools for a series of fortnightly community workshops in annual cycles at village level. The roll-back malaria principle of diagnosis, treatment and use of long-lasting insecticidal nets was a central component of the workshops. Structural house improvement to reduce entry of malaria vectors consisted of targeted activities in selected villages to mobilize the community into voluntarily closing the eaves and screening the windows of their houses; the project provided wire mesh for screening. Corrective measures were introduced to respond to field challenges. Committees were established at village level to coordinate the house improvement activities. Larval source management (LSM) in selected villages consisted of two parts: one on removal of standing water bodies by the community at large; and one on larviciding with bacterial insecticide Bacillus thuringiensis israelensis by trained village committees. Community workshops on malaria were implemented as ‘core intervention’ in all villages. House improvement and LSM were implemented in addition to community workshops on malaria in selected villages. Conclusions Three novel interventions for community mobilization on malaria prevention and control were described. The interventions comprised local organizational structure, education and collective action, and incorporated elements of problem identification, planning and evaluation. These methods could be applicable to other countries and settings. Electronic supplementary material The online version of this article (10.1186/s12936-018-2415-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Henk van den Berg
- Laboratory of Entomology, Wageningen University, PO Box 16, 6700AA, Wageningen, The Netherlands.
| | - Michèle van Vugt
- Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Alinune N Kabaghe
- Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.,College of Medicine, University of Malawi, Blantyre, Malawi
| | | | | | | | | | - Asante Kadama
- College of Medicine, University of Malawi, Blantyre, Malawi
| | - Saidon Banda
- College of Medicine, University of Malawi, Blantyre, Malawi
| | - Tinashe Tizifa
- College of Medicine, University of Malawi, Blantyre, Malawi
| | - Steven Gowelo
- Laboratory of Entomology, Wageningen University, PO Box 16, 6700AA, Wageningen, The Netherlands.,College of Medicine, University of Malawi, Blantyre, Malawi
| | - Monicah M Mburu
- Laboratory of Entomology, Wageningen University, PO Box 16, 6700AA, Wageningen, The Netherlands.,College of Medicine, University of Malawi, Blantyre, Malawi
| | - Kamija S Phiri
- College of Medicine, University of Malawi, Blantyre, Malawi
| | - Willem Takken
- Laboratory of Entomology, Wageningen University, PO Box 16, 6700AA, Wageningen, The Netherlands
| | - Robert S McCann
- Laboratory of Entomology, Wageningen University, PO Box 16, 6700AA, Wageningen, The Netherlands.,College of Medicine, University of Malawi, Blantyre, Malawi
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Mburu MM, Juurlink M, Spitzen J, Moraga P, Hiscox A, Mzilahowa T, Takken W, McCann RS. Impact of partially and fully closed eaves on house entry rates by mosquitoes. Parasit Vectors 2018; 11:383. [PMID: 29970153 PMCID: PMC6029021 DOI: 10.1186/s13071-018-2977-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Accepted: 06/25/2018] [Indexed: 12/02/2022] Open
Abstract
Background Most people infected with malaria acquire the infection indoors from mosquito vectors that entered the house through open eaves, windows and doors. Structural house improvement (e.g. closed eaves and screened windows) is an established method of reducing mosquito entry. It could be complementary to other interventions such as insecticide-treated bed nets (ITNs) for malaria control because it covers and protects all individuals in a house equally. However, when implemented at a large scale, house improvement may not be employed optimally. It is therefore critical to assess whether partial house improvement will have any effect on mosquito house entry. We investigated the effect of partial and complete eave closure on the house-entry rates of malaria vectors and other mosquitoes in southern Malawi. Methods The study was conducted for 25 nights in May-June 2016. Twenty-five traditional houses were modified according to five treatments: fully closed eaves, three different levels of partially closed eaves, and open eaves. All houses had fully screened windows and closed doors. Host-seeking mosquitoes were sampled inside these houses using Centers for Disease Control and Prevention (CDC) light traps. The effect of open eaves versus partial or complete eave closure on the number of mosquitoes trapped inside the house was estimated using a generalized linear mixed model fitted with Poisson distribution and a log-link function. Results House entry by malaria vectors was 14-times higher in houses with fully open eaves compared to houses with fully closed eaves adjusting for wall-type, number of people that slept in the house the previous night, cooking locations and presence of livestock. Houses with four small openings had 9 times more malaria vectors compared to houses with fully closed eaves. The catches of culicine mosquitoes caught in houses with fully closed eaves were not different from those caught in houses with the other treatments. Conclusions Closed eaves resulted in fewer malaria vectors in houses, with differences depending on the degree of eave closure. The ability of malaria vectors to locate any remaining entry points on improved houses, as demonstrated here, suggests that quality control must be an important component of implementing house improvement as an intervention.The lack of effect on culicine mosquitoes in this study could reduce acceptance of house improvement, as implemented here, by household residents due to continued nuisance biting. This limitation could be addressed through community engagement (e.g. encouraging people to close their doors early in the evenings) or improved designs.
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Affiliation(s)
- Monicah M Mburu
- Wageningen University and Research, Wageningen, The Netherlands. .,College of Medicine, University of Malawi, Zomba, Malawi.
| | - Malou Juurlink
- Wageningen University and Research, Wageningen, The Netherlands
| | - Jeroen Spitzen
- Wageningen University and Research, Wageningen, The Netherlands
| | - Paula Moraga
- Centre for Health Informatics, Computing and Statistics (CHICAS), Lancaster Medical School, Lancaster University, Lancaster, UK
| | | | - Themba Mzilahowa
- College of Medicine, University of Malawi, Zomba, Malawi.,MAC Communicable Diseases Action Centre, College of Medicine, Blantyre, Malawi
| | - Willem Takken
- Wageningen University and Research, Wageningen, The Netherlands
| | - Robert S McCann
- Wageningen University and Research, Wageningen, The Netherlands.,College of Medicine, University of Malawi, Zomba, Malawi
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Schoelitsz B, Poortvliet PM, Takken W. Factors driving public tolerance levels and information-seeking behaviour concerning insects in the household environment. Pest Manag Sci 2018; 74:1478-1493. [PMID: 29274106 PMCID: PMC5969102 DOI: 10.1002/ps.4839] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 12/17/2017] [Accepted: 12/17/2017] [Indexed: 06/07/2023]
Abstract
BACKGROUND The public's negative attitudes towards household insects drive tolerance for these insects and their control. Tolerance levels are important in integrated pest management (IPM), as are pest knowledge and information. The risk information seeking and processing (RISP) model describes the relationships between personal factors and information-seeking behaviour. We combined IPM and RISP to determine important relationships between factors driving insect tolerance levels and information-seeking behaviour through an online survey and tested whether this model is valid and generally applicable. RESULTS Relationships between variables from both IPM and RISP models were tested for seven insect species. Tolerance levels were measured with two factors: willingness to pay for pest control and whether insects are tolerated. Willingness to pay for control was positively affected by age, experience, risk perception, insect characteristics, and negative emotions and affected behavioural intention, by influencing information sufficiency and information-seeking behaviour. Tolerability was influenced by perception of insect characteristics and determines whether control measures are taken. CONCLUSION It was possible to combine the RISP and IPM models. Relevant driving factors were a person's age, experience, risk perception, negative affective responses, tolerance levels, relevant channel beliefs about online forums, information sufficiency and information-seeking behaviour. There was, however, variation in important factors between different insects. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
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Affiliation(s)
- Bruce Schoelitsz
- Kennis‐ en Adviescentrum DierplagenWageningenThe Netherlands
- Laboratory of EntomologyWageningen University and ResearchWageningenThe Netherlands
| | - P Marijn Poortvliet
- Strategic CommunicationWageningen University and ResearchWageningenThe Netherlands
| | - Willem Takken
- Laboratory of EntomologyWageningen University and ResearchWageningenThe Netherlands
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43
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Hakizimana E, Karema C, Munyakanage D, Githure J, Mazarati JB, Tongren JE, Takken W, Binagwaho A, Koenraadt CJ. Spatio-temporal distribution of mosquitoes and risk of malaria infection in Rwanda. Acta Trop 2018; 182:149-157. [PMID: 29476726 DOI: 10.1016/j.actatropica.2018.02.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 01/26/2018] [Accepted: 02/11/2018] [Indexed: 11/24/2022]
Abstract
To date, the Republic of Rwanda has not systematically reported on distribution, diversity and malaria infectivity rate of mosquito species throughout the country. Therefore, we assessed the spatial and temporal variation of mosquitoes in the domestic environment, as well as the nocturnal biting behavior and infection patterns of the main malaria vectors in Rwanda. For this purpose, mosquitoes were collected monthly from 2010 to 2013 by human landing catches (HLC) and pyrethrum spray collections (PSC) in seven sentinel sites. Mosquitoes were identified using morphological characteristics and PCR. Plasmodium falciparum sporozoite infection rates were determined using ELISA. A total of 340,684 mosquitoes was collected by HLC and 73.8% were morphologically identified as culicines and 26.2% as anophelines. Of the latter, 94.3% were Anopheles gambiae s.l., 0.4% Anopheles funestus and 5.3% other Anopheles species. Of An. gambiae s.l., An. arabiensis and An. gambiae s.s. represented 84.4% and 15.6%, respectively. Of all An. gambiae s.l. collected indoor and outdoor, the proportion collected indoors was 51.3% in 2010 and 44.9% in 2013. A total of 17,022 mosquitoes was collected by PSC of which 20.5% were An. gambiae s.l. and 79.5% were culicines. For the seven sentinel sites, the mean indoor density for An. gambiae s.l. varied from 0.0 to 1.0 mosquitoes/house/night. P. falciparum infection rates in mosquitoes varied from 0.87 to 4.06%. The entomological inoculation rate (EIR) ranged from 1.0 to 329.8 with an annual average of 99.5 infective bites/person/year. This longitudinal study shows, for the first time, the abundance, species composition, and entomological inoculation rate of malaria mosquitoes collected throughout Rwanda.
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Abstract
The health impact of mosquito-borne diseases causes a huge burden on human societies. Recent vector control campaigns have resulted in promising declines in incidence and prevalence of these diseases, notably malaria, but resistance to insecticides and drugs are on the rise, threatening to overturn these gains. Moreover, several vector-borne diseases have re-emerged, requiring prompt and effective response measures. To improve and properly implement vector control interventions, the behaviour of the vectors must be well understood with detailed examination of mosquito flight being an essential component. Current knowledge on mosquito behaviour across its life history is briefly presented, followed by an overview of recent developments in automated tracking techniques for detailed interpretation of mosquito behaviour. These techniques allow highly accurate recording and observation of mating, feeding and oviposition behaviour. Software programmes built with specific algorithms enable quantification of these behaviours. For example, the crucial role of heat on host landing and the multimodal integration of carbon dioxide (CO2) with other host cues, has been unravelled based on three-dimensional tracking of mosquito flight behaviour. Furthermore, the behavioural processes underlying house entry and subsequent host searching and finding can be better understood by analysis of detailed flight recordings. Further potential of these technologies to solve knowledge gaps is discussed. The use of tracking techniques can support or replace existing monitoring tools and provide insights on mosquito behaviour that can lead to innovative and more effective vector-control measures.
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Affiliation(s)
- Jeroen Spitzen
- Laboratory of Entomology, Wageningen University and Research, PO Box 16, 6700 AA Wageningen, The Netherlands
| | - Willem Takken
- Laboratory of Entomology, Wageningen University and Research, PO Box 16, 6700 AA Wageningen, The Netherlands
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45
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Affiliation(s)
| | - Willem Takken
- Laboratory of Entomology, Wageningen University, 6700 AA, Netherlands
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46
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Verhulst NO, Umanets A, Weldegergis BT, Maas JPA, Visser TM, Dicke M, Smidt H, Takken W. Do apes smell like humans? The role of skin bacteria and volatiles of primates in mosquito host selection. J Exp Biol 2018; 221:jeb.185959. [DOI: 10.1242/jeb.185959] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 09/20/2018] [Indexed: 12/16/2022]
Abstract
Anthropophilic mosquitoes are effective vectors of human diseases because of their biting preference. To find their host, these mosquitoes are guided by human odours, primarily produced by human skin bacteria. By analysing the skin bacterial and skin volatile profiles of humans, bonobos, chimpanzees, gorillas, lemurs and cows, we investigated whether primates that are more closely related to humans have a skin bacterial community and odour profile that is similar to humans. We then investigated whether this affected discrimination between humans and closely related primates by anthropophilic and zoophilic mosquitoes that search for hosts. Humans had a lower skin bacterial diversity than the other animals and their skin bacterial composition was more similar to the other primates than to the skin bacterial composition of cows. Like the skin bacterial profiles, the volatile profiles of the animal groups were clearly different from each other. The cow and lemur volatile profiles were more closely related to the human profiles than expected. Human volatiles were indeed preferred above cow volatiles by anthropophilic mosquitoes and no preference was observed when tested against non-human primate odour, except for bonobo volatiles that were preferred over human volatiles. Unravelling the differences between mosquito hosts and their effect on host selection is important for a better understanding of cross-species transmission of vector-borne diseases.
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Affiliation(s)
- Niels O. Verhulst
- Laboratory of Entomology, Wageningen University & Research, P.O. Box 16, 6700 AA Wageningen, the Netherlands
- National Centre for Vector Entomology, Institute of Parasitology, Faculty of Veterinary Science (Vetsuisse), University of Zurich, Zurich, Switzerland
| | - Alexander Umanets
- Laboratory of Microbiology, Wageningen University & Research, P.O. Box 8033, 6700 EH, Wageningen, the Netherlands
| | - Berhane T. Weldegergis
- Laboratory of Entomology, Wageningen University & Research, P.O. Box 16, 6700 AA Wageningen, the Netherlands
| | - Jeroen P. A. Maas
- Laboratory of Entomology, Wageningen University & Research, P.O. Box 16, 6700 AA Wageningen, the Netherlands
| | - Tessa M. Visser
- Laboratory of Entomology, Wageningen University & Research, P.O. Box 16, 6700 AA Wageningen, the Netherlands
| | - Marcel Dicke
- Laboratory of Entomology, Wageningen University & Research, P.O. Box 16, 6700 AA Wageningen, the Netherlands
| | - Hauke Smidt
- National Centre for Vector Entomology, Institute of Parasitology, Faculty of Veterinary Science (Vetsuisse), University of Zurich, Zurich, Switzerland
| | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, P.O. Box 16, 6700 AA Wageningen, the Netherlands
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47
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Garcia-Martí I, Zurita-Milla R, van Vliet AJH, Takken W. Modelling and mapping tick dynamics using volunteered observations. Int J Health Geogr 2017; 16:41. [PMID: 29137670 PMCID: PMC5686904 DOI: 10.1186/s12942-017-0114-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2017] [Accepted: 11/01/2017] [Indexed: 12/05/2022] Open
Abstract
Background Tick populations and tick-borne infections have steadily increased since the mid-1990s posing an ever-increasing risk to public health. Yet, modelling tick dynamics remains challenging because of the lack of data and knowledge on this complex phenomenon. Here we present an approach to model and map tick dynamics using volunteered data. This approach is illustrated with 9 years of data collected by a group of trained volunteers who sampled active questing ticks (AQT) on a monthly basis and for 15 locations in the Netherlands. We aimed at finding the main environmental drivers of AQT at multiple time-scales, and to devise daily AQT maps at the national level for 2014. Method Tick dynamics is a complex ecological problem driven by biotic (e.g. pathogens, wildlife, humans) and abiotic (e.g. weather, landscape) factors. We enriched the volunteered AQT collection with six types of weather variables (aggregated at 11 temporal scales), three types of satellite-derived vegetation indices, land cover, and mast years. Then, we applied a feature engineering process to derive a set of 101 features to characterize the conditions that yielded a particular count of AQT on a date and location. To devise models predicting the AQT, we use a time-aware Random Forest regression method, which is suitable to find non-linear relationships in complex ecological problems, and provides an estimation of the most important features to predict the AQT. Results We trained a model capable of fitting AQT with reduced statistical metrics. The multi-temporal study on the feature importance indicates that variables linked to water levels in the atmosphere (i.e. evapotranspiration, relative humidity) consistently showed a higher explanatory power than previous works using temperature. As a product of this study, we are able of mapping daily tick dynamics at the national level. Conclusions This study paves the way towards the design of new applications in the fields of environmental research, nature management, and public health. It also illustrates how Citizen Science initiatives produce geospatial data collections that can support scientific analysis, thus enabling the monitoring of complex environmental phenomena.
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Affiliation(s)
- Irene Garcia-Martí
- Department of Geo-Information Processing (GIP), Faculty of Geo-Information and Earth Observation (ITC), University of Twente, Enschede, The Netherlands.
| | - Raúl Zurita-Milla
- Department of Geo-Information Processing (GIP), Faculty of Geo-Information and Earth Observation (ITC), University of Twente, Enschede, The Netherlands
| | - Arnold J H van Vliet
- Department of Environmental Sciences, Wageningen University, Wageningen, The Netherlands
| | - Willem Takken
- Department of Plant Sciences, Wageningen University, Wageningen, The Netherlands
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48
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Ingabire CM, Hakizimana E, Rulisa A, Kateera F, Van Den Borne B, Muvunyi CM, Mutesa L, Van Vugt M, Koenraadt CJM, Takken W, Alaii J. Community-based biological control of malaria mosquitoes using Bacillus thuringiensis var. israelensis (Bti) in Rwanda: community awareness, acceptance and participation. Malar J 2017; 16:399. [PMID: 28974204 PMCID: PMC5627396 DOI: 10.1186/s12936-017-2046-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Accepted: 09/26/2017] [Indexed: 12/04/2022] Open
Abstract
Background Targeting the aquatic stages of malaria vectors via larval source management (LSM) in collaboration with local communities could accelerate progress towards malaria elimination when deployed in addition to existing vector control strategies. However, the precise role that communities can assume in implementing such an intervention has not been fully investigated. This study investigated community awareness, acceptance and participation in a study that incorporated the socio-economic and entomological impact of LSM using Bacillus thuringiensis var. israelensis (Bti) in eastern Rwanda, and identified challenges and recommendations for future scale-up. Methods The implementation of the community-based LSM intervention took place in Ruhuha, Rwanda, from February to July 2015. The intervention included three arms: control, community-based (CB) and project-supervised (PS). Mixed methods were used to collect baseline and endline socio-economic data in January and October 2015. Results A high perceived safety and effectiveness of Bti was reported at the start of the intervention. Being aware of malaria symptoms and perceiving Bti as safe on other living organisms increased the likelihood of community participation through investment of labour time for Bti application. On the other hand, the likelihood for community participation was lower if respondents: (1) perceived rice farming as very profitable; (2) provided more money to the cooperative as a capital; and, (3) were already involved in rice farming for more than 6 years. After 6 months of implementation, an increase in knowledge and skills regarding Bti application was reported. The community perceived a reduction in mosquito density and nuisance biting on treated arms. Main operational, seasonal and geographical challenges included manual application of Bti, long working hours, and need for transportation for reaching the fields. Recommendations were made for future scale-up, including addressing above-mentioned concerns and government adoption of LSM as part of its vector control strategies. Conclusions Community awareness and support for LSM increased following Bti application. A high effectiveness of Bti in terms of reduction of mosquito abundance and nuisance biting was perceived. The study confirmed the feasibility of community-based LSM interventions and served as evidence for future scale-up of Bti application and adoption into Rwandan malaria vector control strategies.
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Affiliation(s)
- Chantal Marie Ingabire
- Department of Health Promotion, Maastricht University, Maastricht, The Netherlands. .,Medical Research Center, Rwanda Biomedical Center, Kigali, Rwanda.
| | - Emmanuel Hakizimana
- Malaria & Other Parasitic Diseases Division, Rwanda Biomedical Center, Kigali, Rwanda.,Laboratory of Entomology, Wageningen University, Wageningen, The Netherlands
| | - Alexis Rulisa
- Medical Research Center, Rwanda Biomedical Center, Kigali, Rwanda.,Department of Cultural Anthropology and Development Studies, Radboud University Nijmegen, Nijmegen, The Netherlands
| | - Fredrick Kateera
- Medical Research Center, Rwanda Biomedical Center, Kigali, Rwanda.,Academic Medical Center, Amsterdam, The Netherlands
| | - Bart Van Den Borne
- Department of Health Promotion, Maastricht University, Maastricht, The Netherlands
| | | | - Leon Mutesa
- College of Medicine and Health Sciences, University of Rwanda, Kigali, Rwanda
| | | | | | - Willem Takken
- Laboratory of Entomology, Wageningen University, Wageningen, The Netherlands
| | - Jane Alaii
- Context Factor Solutions, Nairobi, Kenya
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49
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Athrey G, Cosme LV, Popkin-Hall Z, Pathikonda S, Takken W, Slotman MA. Chemosensory gene expression in olfactory organs of the anthropophilic Anopheles coluzzii and zoophilic Anopheles quadriannulatus. BMC Genomics 2017; 18:751. [PMID: 28938869 PMCID: PMC5610455 DOI: 10.1186/s12864-017-4122-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Accepted: 09/06/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Anopheles (An.) coluzzii, one of Africa's primary malaria vectors, is highly anthropophilic. This human host preference contributes greatly to its ability to transmit malaria. In contrast, the closely related An. quadriannulatus prefers to feed on bovids and is not thought to contribute to malaria transmission. The diverged preference for host odor profiles between these sibling species is likely reflected in chemosensory gene expression levels in the olfactory organs. Therefore, we compared the transcriptomes of the antennae and maxillary palps between An. coluzzii and An. quadriannulatus, focusing on the major chemosensory gene families. RESULTS While chemosensory gene expression is strongly correlated between the two species, various chemosensory genes show significantly enhanced expression in one of the species. In the antennae of An. coluzzii the expression of six olfactory receptors (Ors) and seven ionotropic receptors (Irs) is considerably enhanced, whereas 11 Ors and 3 Irs are upregulated in An. quadriannulatus. In the maxillary palps, leaving aside Irs with very low level of expression, one Ir is strongly enhanced in each species. In addition, we find divergence in odorant binding protein (Obp) gene expression, with several highly expressed Obps being enhanced in the antennae and palps of An. coluzzii. Finally, the expression of several gustatory receptors (Grs) in the palps appears to be species-specific, including a homolog of a sugar-sensing Drosophila Gr. CONCLUSIONS A considerable number of Ors and Irs are differentially expressed between these two closely related species with diverging host preference. These chemosensory genes could play a role in the human host preference of the malaria vector An. coluzzii. Additionally, divergence in Obp expression between the two species suggests a possible role of these odor carrier proteins in determining host preference. Finally, divergence in chemosensory expression in the palps may point towards a possible role for the maxillary palps in host differentiation.
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Affiliation(s)
- G. Athrey
- Department of Poultry Science, Texas A&M University, College Station, TX USA
| | - L. V. Cosme
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT USA
| | - Z. Popkin-Hall
- Department of Entomology, Texas A&M University, College Station, TX 77845 USA
| | - S. Pathikonda
- Department of Entomology, Texas A&M University, College Station, TX 77845 USA
| | - W. Takken
- Laboratory of Entomology, Wageningen University, Wageningen, The Netherlands
| | - M. A. Slotman
- Department of Entomology, Texas A&M University, College Station, TX 77845 USA
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50
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McCann RS, van den Berg H, Diggle PJ, van Vugt M, Terlouw DJ, Phiri KS, Di Pasquale A, Maire N, Gowelo S, Mburu MM, Kabaghe AN, Mzilahowa T, Chipeta MG, Takken W. Assessment of the effect of larval source management and house improvement on malaria transmission when added to standard malaria control strategies in southern Malawi: study protocol for a cluster-randomised controlled trial. BMC Infect Dis 2017; 17:639. [PMID: 28938876 PMCID: PMC5610449 DOI: 10.1186/s12879-017-2749-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Accepted: 09/19/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Due to outdoor and residual transmission and insecticide resistance, long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) will be insufficient as stand-alone malaria vector control interventions in many settings as programmes shift toward malaria elimination. Combining additional vector control interventions as part of an integrated strategy would potentially overcome these challenges. Larval source management (LSM) and structural house improvements (HI) are appealing as additional components of an integrated vector management plan because of their long histories of use, evidence on effectiveness in appropriate settings, and unique modes of action compared to LLINs and IRS. Implementation of LSM and HI through a community-based approach could provide a path for rolling-out these interventions sustainably and on a large scale. METHODS/DESIGN We will implement community-based LSM and HI, as additional interventions to the current national malaria control strategies, using a randomised block, 2 × 2 factorial, cluster-randomised design in rural, southern Malawi. These interventions will be continued for two years. The trial catchment area covers about 25,000 people living in 65 villages. Community participation is encouraged by training community volunteers as health animators, and supporting the organisation of village-level committees in collaboration with The Hunger Project, a non-governmental organisation. Household-level cross-sectional surveys, including parasitological and entomological sampling, will be conducted on a rolling, 2-monthly schedule to measure outcomes over two years (2016 to 2018). Coverage of LSM and HI will also be assessed throughout the trial area. DISCUSSION Combining LSM and/or HI together with the interventions currently implemented by the Malawi National Malaria Control Programme is anticipated to reduce malaria transmission below the level reached by current interventions alone. Implementation of LSM and HI through a community-based approach provides an opportunity for optimum adaptation to the local ecological and social setting, and enhances the potential for sustainability. TRIAL REGISTRATION Registered with The Pan African Clinical Trials Registry on 3 March 2016, trial number PACTR201604001501493.
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Affiliation(s)
- Robert S McCann
- Wageningen University and Research, Wageningen, The Netherlands. .,College of Medicine, University of Malawi, Blantyre, Malawi. .,Laboratory of Entomology, Wageningen University and Research, PO Box 16, 6700, AA, Wageningen, The Netherlands.
| | | | | | - Michèle van Vugt
- Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - Dianne J Terlouw
- Liverpool School of Tropical Medicine, Liverpool, UK.,Malawi-Liverpool Wellcome Trust, Blantyre, Malawi
| | - Kamija S Phiri
- College of Medicine, University of Malawi, Blantyre, Malawi
| | - Aurelio Di Pasquale
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Nicolas Maire
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Steven Gowelo
- College of Medicine, University of Malawi, Blantyre, Malawi
| | - Monicah M Mburu
- Wageningen University and Research, Wageningen, The Netherlands.,College of Medicine, University of Malawi, Blantyre, Malawi
| | - Alinune N Kabaghe
- College of Medicine, University of Malawi, Blantyre, Malawi.,Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | | | - Michael G Chipeta
- College of Medicine, University of Malawi, Blantyre, Malawi.,Lancaster University, Lancaster, UK.,Malawi-Liverpool Wellcome Trust, Blantyre, Malawi
| | - Willem Takken
- Wageningen University and Research, Wageningen, The Netherlands
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