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Mbewe RB, Keven JB, Mangani C, Wilson ML, Mzilahowa T, Mathanga DP, Valim C, Laufer MK, Walker ED, Cohee LM. Genotyping of Anopheles mosquito blood meals reveals nonrandom human host selection: implications for human-to-mosquito Plasmodium falciparum transmission. Malar J 2023; 22:115. [PMID: 37029433 PMCID: PMC10080529 DOI: 10.1186/s12936-023-04541-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Accepted: 03/22/2023] [Indexed: 04/09/2023] Open
Abstract
BACKGROUND Control of malaria parasite transmission can be enhanced by understanding which human demographic groups serve as the infectious reservoirs. Because vector biting can be heterogeneous, some infected individuals may contribute more to human-to-mosquito transmission than others. Infection prevalence peaks in school-age children, but it is not known how often they are fed upon. Genotypic profiling of human blood permits identification of individual humans who were bitten. The present investigation used this method to estimate which human demographic groups were most responsible for transmitting malaria parasites to Anopheles mosquitoes. It was hypothesized that school-age children contribute more than other demographic groups to human-to-mosquito malaria transmission. METHODS In a region of moderate-to-high malaria incidence in southeastern Malawi, randomly selected households were surveyed to collect human demographic information and blood samples. Blood-fed, female Anopheles mosquitoes were sampled indoors from the same houses. Genomic DNA from human blood samples and mosquito blood meals of human origin was genotyped using 24 microsatellite loci. The resultant genotypes were matched to identify which individual humans were sources of blood meals. In addition, Plasmodium falciparum DNA in mosquito abdomens was detected with polymerase chain reaction. The combined results were used to identify which humans were most frequently bitten, and the P. falciparum infection prevalence in mosquitoes that resulted from these blood meals. RESULTS Anopheles females selected human hosts non-randomly and fed on more than one human in 9% of the blood meals. Few humans contributed most of the blood meals to the Anopheles vector population. Children ≤ 5 years old were under-represented in mosquito blood meals while older males (31-75 years old) were over-represented. However, the largest number of malaria-infected blood meals was from school age children (6-15 years old). CONCLUSIONS The results support the hypothesis that humans aged 6-15 years are the most important demographic group contributing to the transmission of P. falciparum to the Anopheles mosquito vectors. This conclusion suggests that malaria control and prevention programmes should enhance efforts targeting school-age children and males.
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Affiliation(s)
- Rex B Mbewe
- Department of Entomology, Michigan State University, East Lansing, MI, USA.
- Department of Physics and Biochemical Sciences, Malawi University of Business and Applied Sciences, Blantyre, Malawi.
| | - John B Keven
- Department of Entomology, Michigan State University, East Lansing, MI, USA
- Department of Public Health, College of Health Sciences, University of California-Irvine, Irvine, CA, USA
| | - Charles Mangani
- Malaria Alert Center, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Mark L Wilson
- Department of Epidemiology, School of Public Health, University of Michigan, Ann Arbor, MI, USA
| | - Themba Mzilahowa
- Malaria Alert Center, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Don P Mathanga
- Malaria Alert Center, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Clarissa Valim
- Department of Global Health, Boston University School of Public Health, Boston, MA, USA
| | - Miriam K Laufer
- Malaria Research Program, Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Edward D Walker
- Department of Entomology, Michigan State University, East Lansing, MI, USA
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA
| | - Lauren M Cohee
- Malaria Research Program, Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, USA
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2
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Brown R, Salgado-Lynn M, Jumail A, Jalius C, Chua TH, Vythilingam I, Ferguson HM. Exposure of Primate Reservoir Hosts to Mosquito Vectors in Malaysian Borneo. ECOHEALTH 2022; 19:233-245. [PMID: 35553290 PMCID: PMC9276546 DOI: 10.1007/s10393-022-01586-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 03/05/2022] [Accepted: 03/10/2022] [Indexed: 06/15/2023]
Abstract
Several vector-borne pathogens of primates have potential for human spillover. An example is the simian malaria Plasmodium knowlesi which is now a major public health problem in Malaysia. Characterization of exposure to mosquito vectors is essential for assessment of the force of infection within wild simian populations, however few methods exist to do so. Here we demonstrate the use of thermal imaging and mosquito magnet independence traps (MMIT) to assess the abundance, diversity and infection rates in mosquitoes host seeking near long-tailed macaque (Macaca fasicularis) sleeping sites in the Lower Kinabatangan Wildlife Sanctuary, Malaysian Borneo. The primary Plasmodium knowlesi vector, Anopheles balabacensis, was trapped at higher abundance near sleeping sites than control trees. Although none of the An. balabacensis collected (n = 15) were positive for P. knowlesi by PCR screening, two were infected with another simian malaria Plasmodium inui. Analysis of macaque stools from sleeping sites confirmed a high prevalence of Plasmodium infection, suspected to be P. inui. Recently, natural transmission of P. inui has been detected in humans and An. cracens in Peninsular Malaysia. The presence of P. inui in An. balabacensis here and previously in human-biting collections highlight its potential for spillover from macaques to humans in Sabah. We advocate the use of MMITs for non-invasive sampling of mosquito vectors that host seek on wild simian populations.
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Affiliation(s)
- Rebecca Brown
- Department of Vector Biology, Liverpool School of Tropical Medicine and Hygiene, Liverpool, L3 5QA, UK.
| | - Milena Salgado-Lynn
- Danau Girang Field Centre C/O Sabah Wildlife Department, Wisma Muis, Kota Kinabalu, Sabah, Malaysia
- School of Biosciences and Sustainable Places Research Institute, Cardiff University, Cardiff, UK
- Wildlife Health, Genetic and Forensic Laboratory, Kampung Potuki, Kota Kinabalu, Sabah, Malaysia
| | - Amaziasizamoria Jumail
- Danau Girang Field Centre C/O Sabah Wildlife Department, Wisma Muis, Kota Kinabalu, Sabah, Malaysia
| | - Cyrlen Jalius
- Wildlife Health, Genetic and Forensic Laboratory, Kampung Potuki, Kota Kinabalu, Sabah, Malaysia
| | - Tock-Hing Chua
- Department of Pathobiology and Medical Diagnostics, Faculty of Medicine and Health Sciences, Universiti Malaysia Sabah, Kota Kinabalu, Sabah, Malaysia
| | - Indra Vythilingam
- Department of Parasitology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Heather M Ferguson
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Graham Kerr Building, University Avenue, Glasgow, G12 8QQ, UK
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3
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Byrne I, Chan K, Manrique E, Lines J, Wolie RZ, Trujillano F, Garay GJ, Del Prado Cortez MN, Alatrista-Salas H, Sternberg E, Cook J, N'Guessan R, Koffi A, Ahoua Alou LP, Apollinaire N, Messenger LA, Kristan M, Carrasco-Escobar G, Fornace K. Technical Workflow Development for Integrating Drone Surveys and Entomological Sampling to Characterise Aquatic Larval Habitats of Anopheles funestus in Agricultural Landscapes in Côte d'Ivoire. JOURNAL OF ENVIRONMENTAL AND PUBLIC HEALTH 2021; 2021:3220244. [PMID: 34759971 PMCID: PMC8575637 DOI: 10.1155/2021/3220244] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 10/07/2021] [Indexed: 11/17/2022]
Abstract
Land-use practices such as agriculture can impact mosquito vector breeding ecology, resulting in changes in disease transmission. The typical breeding habitats of Africa's second most important malaria vector Anopheles funestus are large, semipermanent water bodies, which make them potential candidates for targeted larval source management. This is a technical workflow for the integration of drone surveys and mosquito larval sampling, designed for a case study aiming to characterise An. funestus breeding sites near two villages in an agricultural setting in Côte d'Ivoire. Using satellite remote sensing data, we developed an environmentally and spatially representative sampling frame and conducted paired mosquito larvae and drone mapping surveys from June to August 2021. To categorise the drone imagery, we also developed a land cover classification scheme with classes relative to An. funestus breeding ecology. We sampled 189 potential breeding habitats, of which 119 (63%) were positive for the Anopheles genus and nine (4.8%) were positive for An. funestus. We mapped 30.42 km2 of the region of interest including all water bodies which were sampled for larvae. These data can be used to inform targeted vector control efforts, although its generalisability over a large region is limited by the fine-scale nature of this study area. This paper develops protocols for integrating drone surveys and statistically rigorous entomological sampling, which can be adjusted to collect data on vector breeding habitats in other ecological contexts. Further research using data collected in this study can enable the development of deep-learning algorithms for identifying An. funestus breeding habitats across rural agricultural landscapes in Côte d'Ivoire and the analysis of risk factors for these sites.
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Affiliation(s)
- Isabel Byrne
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK
| | - Kallista Chan
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK
- Centre on Climate Change and Planetary Health, London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK
| | - Edgar Manrique
- Health Innovation Laboratory, Institute of Tropical Medicine “Alexander von Humboldt”, Universidad Peruana Cayetano Heredia, Lima, Peru
- Laboratorio ICEMR-Amazonia, Laboratorios de Investigación y Desarrollo, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Jo Lines
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK
- Centre on Climate Change and Planetary Health, London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK
| | - Rosine Z. Wolie
- Institut Pierre Richet, Bouaké, Côte d'Ivoire
- Laboratoire de génétique, Unité de Formation et de Recherche en Biosciences, Université Félix Houphouët Boigny, Abidjan, Côte d'Ivoire
| | | | | | | | | | - Eleanore Sternberg
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Jackie Cook
- Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK
| | - Raphael N'Guessan
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK
- Institut Pierre Richet, Bouaké, Côte d'Ivoire
| | | | | | | | - Louisa A. Messenger
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK
| | - Mojca Kristan
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK
| | - Gabriel Carrasco-Escobar
- Health Innovation Laboratory, Institute of Tropical Medicine “Alexander von Humboldt”, Universidad Peruana Cayetano Heredia, Lima, Peru
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA
| | - Kimberly Fornace
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK
- Centre on Climate Change and Planetary Health, London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK
- Institute of Biodiversity, Animal Health & Comparative Medicine, University of Glasgow, Glasgow, UK
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4
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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] [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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5
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Yaro JB, Tiono AB, Sanou A, Toe HK, Bradley J, Ouedraogo A, Ouedraogo ZA, Guelbeogo MW, Agboraw E, Worrall E, Sagnon N'F, Lindsay SW, Wilson AL. Risk factors associated with house entry of malaria vectors in an area of Burkina Faso with high, persistent malaria transmission and high insecticide resistance. Malar J 2021; 20:397. [PMID: 34629053 PMCID: PMC8504047 DOI: 10.1186/s12936-021-03926-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 09/26/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In rural Burkina Faso, the primary malaria vector Anopheles gambiae sensu lato (s.l.) primarily feeds indoors at night. Identification of factors which influence mosquito house entry could lead to development of novel malaria vector control interventions. A study was therefore carried out to identify risk factors associated with house entry of An. gambiae s.l. in south-west Burkina Faso, an area of high insecticide resistance. METHODS Mosquitoes were sampled monthly during the malaria transmission season using CDC light traps in 252 houses from 10 villages, each house sleeping at least one child aged five to 15 years old. Potential risk factors for house entry of An. gambiae s.l. were measured, including socio-economic status, caregiver's education and occupation, number of people sleeping in the same part of the house as the child, use of anti-mosquito measures, house construction and fittings, proximity of anopheline aquatic habitats and presence of animals near the house. Mosquito counts were compared using a generalized linear mixed-effect model with negative binomial and log link function, adjusting for repeated collections. RESULTS 20,929 mosquitoes were caught, of which 16,270 (77.7%) were An. gambiae s.l. Of the 6691 An. gambiae s.l. identified to species, 4101 (61.3%) were An. gambiae sensu stricto and 2590 (38.7%) Anopheles coluzzii. Having a metal-roof on the child's sleeping space (IRR = 0.55, 95% CI 0.32-0.95, p = 0.03) was associated with fewer malaria vectors inside the home. CONCLUSION This study demonstrated that the rate of An. gambiae s.l. was 45% lower in sleeping spaces with a metal roof, compared to those with thatch roofs. Improvements in house construction, including installation of metal roofs, should be considered in endemic areas of Africa to reduce the burden of malaria.
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Affiliation(s)
- Jean Baptiste Yaro
- Centre National de Recherche Et de Formation Sur Le Paludisme, Ouagadougou, Burkina Faso.,Department of Biosciences, Durham University, Durham, UK
| | - Alfred B Tiono
- Centre National de Recherche Et de Formation Sur Le Paludisme, Ouagadougou, Burkina Faso
| | - Antoine Sanou
- Centre National de Recherche Et de Formation Sur Le Paludisme, Ouagadougou, Burkina Faso
| | - Hyacinthe K Toe
- Centre National de Recherche Et de Formation Sur Le Paludisme, Ouagadougou, Burkina Faso
| | - John Bradley
- MRC International Statistics and Epidemiology Group, London School of Hygiene and Tropical Medicine, London, UK
| | - Alphonse Ouedraogo
- Centre National de Recherche Et de Formation Sur Le Paludisme, Ouagadougou, Burkina Faso
| | - Z Amidou Ouedraogo
- Centre National de Recherche Et de Formation Sur Le Paludisme, Ouagadougou, Burkina Faso
| | - Moussa W Guelbeogo
- Centre National de Recherche Et de Formation Sur Le Paludisme, Ouagadougou, Burkina Faso
| | - Efundem Agboraw
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Eve Worrall
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - N 'Fale Sagnon
- Centre National de Recherche Et de Formation Sur Le Paludisme, Ouagadougou, Burkina Faso
| | | | - Anne L Wilson
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK.
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6
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Eba K, Habtewold T, Yewhalaw D, Christophides GK, Duchateau L. Anopheles arabiensis hotspots along intermittent rivers drive malaria dynamics in semi-arid areas of Central Ethiopia. Malar J 2021; 20:154. [PMID: 33731115 PMCID: PMC7971958 DOI: 10.1186/s12936-021-03697-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 03/11/2021] [Indexed: 11/30/2022] Open
Abstract
Background Understanding malaria vector’s population dynamics and their spatial distribution is important to define when and where the largest infection risks occur and implement appropriate control strategies. In this study, the seasonal spatio-temporal dynamics of the malaria vector population and transmission intensity along intermittent rivers in a semi-arid area of central Ethiopia were investigated. Methods Mosquitoes were collected monthly from five clusters, 2 close to a river and 3 away from a river, using pyrethrum spray catches from November 2014 to July 2016. Mosquito abundance was analysed by the mixed Poisson regression model. The human blood index and sporozoite rate was compared between seasons by a logistic regression model. Results A total of 2784 adult female Anopheles gambiae sensu lato (s.l.) were collected during the data collection period. All tested mosquitoes (n = 696) were identified as Anopheles arabiensis by polymerase chain reaction. The average daily household count was significantly higher (P = 0.037) in the clusters close to the river at 5.35 (95% CI 2.41–11.85) compared to the clusters away from the river at 0.033 (95% CI 0.02–0.05). Comparing the effect of vicinity of the river by season, a significant effect of closeness to the river was found during the dry season (P = 0.027) and transition from dry to wet season (P = 0.032). Overall, An. arabiensis had higher bovine blood index (62.8%) as compared to human blood index (23.8%), ovine blood index (9.2%) and canine blood index (0.1%). The overall sporozoite rate was 3.9% and 0% for clusters close to and away from the river, respectively. The overall Plasmodium falciparum and Plasmodium vivax entomologic inoculation rates for An. arabiensis in clusters close to the river were 0.8 and 2.2 infective bites per person/year, respectively. Conclusion Mosquito abundance and malaria transmission intensity in clusters close to the river were higher which could be attributed to the riverine breeding sites. Thus, vector control interventions including targeted larval source management should be implemented to reduce the risk of malaria infection in the area. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-021-03697-z.
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Affiliation(s)
- Kasahun Eba
- Biometrics Research Centre, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.,Department of Environmental Health Science and Technology, Jimma University, P.O. Box 378, Jimma, Ethiopia
| | - Tibebu Habtewold
- Department of Life Sciences, Imperial College London, London, UK
| | - Delenasaw Yewhalaw
- School of Medical Laboratory Sciences, Jimma University, P.O.Box 378, Jimma, Ethiopia.,Tropical and Infectious Diseases Research Center, Jimma University, P.O.Box 378, Jimma, Ethiopia
| | | | - Luc Duchateau
- Biometrics Research Centre, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
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7
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Genotyping cognate Plasmodium falciparum in humans and mosquitoes to estimate onward transmission of asymptomatic infections. Nat Commun 2021; 12:909. [PMID: 33568678 PMCID: PMC7875998 DOI: 10.1038/s41467-021-21269-2] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 01/15/2021] [Indexed: 01/30/2023] Open
Abstract
Malaria control may be enhanced by targeting reservoirs of Plasmodium falciparum transmission. One putative reservoir is asymptomatic malaria infections and the scale of their contribution to transmission in natural settings is not known. We assess the contribution of asymptomatic malaria to onward transmission using a 14-month longitudinal cohort of 239 participants in a high transmission site in Western Kenya. We identify P. falciparum in asymptomatically- and symptomatically-infected participants and naturally-fed mosquitoes from their households, genotype all parasites using deep sequencing of the parasite genes pfama1 and pfcsp, and use haplotypes to infer participant-to-mosquito transmission through a probabilistic model. In 1,242 infections (1,039 in people and 203 in mosquitoes), we observe 229 (pfcsp) and 348 (pfama1) unique parasite haplotypes. Using these to link human and mosquito infections, compared with symptomatic infections, asymptomatic infections more than double the odds of transmission to a mosquito among people with both infection types (Odds Ratio: 2.56; 95% Confidence Interval (CI): 1.36-4.81) and among all participants (OR 2.66; 95% CI: 2.05-3.47). Overall, 94.6% (95% CI: 93.1-95.8%) of mosquito infections likely resulted from asymptomatic infections. In high transmission areas, asymptomatic infections are the major contributor to mosquito infections and may be targeted as a component of transmission reduction.
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8
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Keven JB, Katusele M, Vinit R, Koimbu G, Vincent N, Thomsen EK, Karl S, Reimer LJ, Walker ED. Species abundance, composition, and nocturnal activity of female Anopheles (Diptera: Culicidae) in malaria-endemic villages of Papua New Guinea: assessment with barrier screen sampling. Malar J 2019; 18:96. [PMID: 30909928 PMCID: PMC6434780 DOI: 10.1186/s12936-019-2742-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Accepted: 03/21/2019] [Indexed: 11/18/2022] Open
Abstract
Background Community composition of Anopheles mosquitoes, and their host-seeking and peridomestic behaviour, are important factors affecting malaria transmission. In this study, barrier screen sampling was used to investigate species composition, abundance, and nocturnal activity of Anopheles populations in villages of Papua New Guinea. Methods Mosquitoes were sampled from 6 pm to 6 am in five villages from 2012 to 2016. The barrier screens were positioned between the village houses and the perimeter of villages where cultivated and wild vegetation (“the bush”) grew thickly. Female Anopheles that rested on either village or bush side of the barrier screens, as they commuted into and out of the villages, were captured. Similarity in species composition among villages was assessed. Mosquitoes captured on village and bush sides of the barrier screens were sorted by feeding status and by hour of collection, and their numbers were compared using negative binomial generalized linear models. Results Females of seven Anopheles species were present in the sample. Species richness ranged from four to six species per village, but relative abundance was highly uneven within and between villages, and community composition was similar for two pairs of villages and highly dissimilar in a fifth. For most Anopheles populations, more unfed than blood-fed mosquitoes were collected from the barrier screens. More blood-fed mosquitoes were found on the side of the barrier screens facing the village and relatively more unfed ones on the bush side, suggesting commuting behaviour of unfed host-seeking females into the villages from nearby bush and commuting of blood-fed females away from villages towards the bush. For most populations, the majority of host-seeking mosquitoes arrived in the village before midnight when people were active and unprotected from the mosquitoes by bed nets. Conclusion The uneven distribution of Anopheles species among villages, with each site dominated by different species, even among nearby villages, emphasizes the importance of vector heterogeneity in local malaria transmission and control. Yet, for most species, nocturnal activity patterns of village entry and host seeking predominantly occurred before midnight indicating common behaviours across species and populations relative to human risk of exposure to Anopheles bites. Electronic supplementary material The online version of this article (10.1186/s12936-019-2742-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- John B Keven
- Vector Borne Diseases Unit, Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea. .,Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA.
| | - Michelle Katusele
- Vector Borne Diseases Unit, Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Rebecca Vinit
- Vector Borne Diseases Unit, Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Gussy Koimbu
- Vector Borne Diseases Unit, Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Naomi Vincent
- Vector Borne Diseases Unit, Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | | | - Stephan Karl
- Vector Borne Diseases Unit, Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea.,Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia.,Department of Medical Biology, Melbourne University, Parkville, VIC, Australia
| | - Lisa J Reimer
- Liverpool School of Tropical Medicine, Liverpool, UK
| | - Edward D Walker
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA
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Charlwood JD, Kessy E, Yohannes K, Protopopoff N, Rowland M, LeClair C. Studies on the resting behaviour and host choice of Anopheles gambiae and An. arabiensis from Muleba, Tanzania. MEDICAL AND VETERINARY ENTOMOLOGY 2018; 32:263-270. [PMID: 29479733 DOI: 10.1111/mve.12299] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Revised: 11/09/2017] [Accepted: 12/15/2017] [Indexed: 06/08/2023]
Abstract
The relative efficacy of a mechanical (Prokopack) collection method vs. manual aspiration in the collection of resting mosquitoes was evaluated in northern Tanzania before and after an intervention using indoor residual spraying and longlasting insecticide-treated nets. In smoke-free houses mosquitoes were collected from the roof and walls, but in smoky houses mosquitoes were found predominantly on the walls. Anopheles gambiae (Diptera: Culicidae) constituted 97.7% of the 312 An. gambiae complex specimens identified before but only 19.3% of the 183 identified after the intervention. A single sampling with the Prokopack collected a third of the available insects. Anopheles gambiae completed its gonotrophic development indoors, whereas Anopheles arabiensis did so outdoors. In both species gonotrophic development took 2 days. Most unfed resting An. arabiensis collected outdoors were virgins, whereas the majority of engorged insects were parous (with well-contracted sacs). Daily survival was estimated to be 80.0%. Only 9.4% of the engorged An. arabiensis collected outdoors and 47.1% of those collected indoors had fed on humans. Using the Prokopack sampler is more efficient than manual methods for the collection of resting mosquitoes. Malaria transmission may have been affected by a change in vector composition resulting from a change in feeding, rather than reduced survival. Monitoring the proportions of members of the An. gambiae complex may provide signals of an impending breakdown in control.
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Affiliation(s)
- J D Charlwood
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, U.K
| | - E Kessy
- Kilimanjaro Christian Medical University College, Moshi, Tanzania
| | - K Yohannes
- Pan African Malaria Vector Research Consortium, Muleba, Tanzania
| | - N Protopopoff
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, U.K
| | - M Rowland
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, U.K
| | - C LeClair
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, U.K
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10
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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] [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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Dear NF, Kadangwe C, Mzilahowa T, Bauleni A, Mathanga DP, Duster C, Walker ED, Wilson ML. Household-level and surrounding peri-domestic environmental characteristics associated with malaria vectors Anopheles arabiensis and Anopheles funestus along an urban-rural continuum in Blantyre, Malawi. Malar J 2018; 17:229. [PMID: 29884176 PMCID: PMC5994107 DOI: 10.1186/s12936-018-2375-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2018] [Accepted: 06/05/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Malaria is increasing in some recently urbanized areas that historically were considered lower risk. Understanding what drives urban transmission is hampered by inconsistencies in how "urban" contexts are defined. A dichotomized "urban-rural" approach, based on political boundaries may misclassify environments or fail to capture local drivers of risk. Small-scale agriculture in urban or peri-urban settings has been shown to be a major risk determinant. METHODS Household-level Anopheles abundance patterns in and around Malawi's commercial capital of Blantyre (~ 1.9 M pop.) were analysed. Clusters (N = 64) of five houses each located at 2.5 km intervals along eight transects radiating out from Blantyre city centre were sampled during rainy and dry seasons of 2015 and 2016. Mosquito densities were measured inside houses using aspirators to sample resting mosquitoes, and un-baited CDC light traps to sample host seeking mosquitoes. RESULTS Of 38,895 mosquitoes captured, 91% were female and 87% were Culex spp. Anopheles females (N = 5058) were primarily captured in light traps (97%). Anopheles abundance was greater during rainy seasons. Anopheles funestus was more abundant than Anopheles arabiensis, but both were found on all transects, and had similar associations with environmental risk factors. Anopheles funestus and An. arabiensis females significantly increased with distance from the urban centre, but this trend was not consistent across all transects. Presence of small-scale agriculture was predictive of greater Anopheles spp. abundance, even after controlling for urbanicity, number of nets per person, number of under-5-year olds, years of education, and season. CONCLUSIONS This study revealed how small-scale agriculture along a rural-to-urban transition was associated with An. arabiensis and An. funestus indoor abundances, and that indoor Anopheles density can be high within Blantyre city limits, particularly where agriculture is present. Typical rural areas with lower house density and greater distance from urban centres reflected landscapes more suitable for Anopheles reproduction and house invasion. However, similar characteristics and elevated Anopheles abundances were also found around some houses within the city limits. Thus, dichotomous designations of "urban" or "rural" can obscure important heterogeneity in the landscape of Plasmodium transmission, suggesting the need for more nuanced assessment of urban malaria risk and prevention efforts.
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Affiliation(s)
- Nicole F Dear
- Department of Epidemiology, School of Public Health, University of Michigan, Ann Arbor, MI, USA.
| | - Chifundo Kadangwe
- Malaria Alert Centre, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Themba Mzilahowa
- Malaria Alert Centre, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Andy Bauleni
- Malaria Alert Centre, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Don P Mathanga
- Malaria Alert Centre, College of Medicine, University of Malawi, Blantyre, Malawi.,College of Medicine, University of Malawi, Blantyre, Malawi
| | - Chifundo Duster
- Malawi International Center of Excellence for Malaria Research (ICEMR) Molecular Core Laboratory, University of Malawi College of Medicine, Blantyre, Malawi
| | - Edward D Walker
- Department of Microbiology & Molecular Genetics, Michigan State University, East Lansing, MI, USA
| | - Mark L Wilson
- Department of Epidemiology, School of Public Health, University of Michigan, Ann Arbor, MI, USA
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