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Sánchez C. HM, Smith DL, Marshall JM. MGSurvE: A framework to optimize trap placement for genetic surveillance of mosquito populations. PLoS Comput Biol 2024; 20:e1012046. [PMID: 38709820 PMCID: PMC11098508 DOI: 10.1371/journal.pcbi.1012046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 05/16/2024] [Accepted: 04/02/2024] [Indexed: 05/08/2024] Open
Abstract
Genetic surveillance of mosquito populations is becoming increasingly relevant as genetics-based mosquito control strategies advance from laboratory to field testing. Especially applicable are mosquito gene drive projects, the potential scale of which leads monitoring to be a significant cost driver. For these projects, monitoring will be required to detect unintended spread of gene drive mosquitoes beyond field sites, and the emergence of alternative alleles, such as drive-resistant alleles or non-functional effector genes, within intervention sites. This entails the need to distribute mosquito traps efficiently such that an allele of interest is detected as quickly as possible-ideally when remediation is still viable. Additionally, insecticide-based tools such as bednets are compromised by insecticide-resistance alleles for which there is also a need to detect as quickly as possible. To this end, we present MGSurvE (Mosquito Gene SurveillancE): a computational framework that optimizes trap placement for genetic surveillance of mosquito populations such that the time to detection of an allele of interest is minimized. A key strength of MGSurvE is that it allows important biological features of mosquitoes and the landscapes they inhabit to be accounted for, namely: i) resources required by mosquitoes (e.g., food sources and aquatic breeding sites) can be explicitly distributed through a landscape, ii) movement of mosquitoes may depend on their sex, the current state of their gonotrophic cycle (if female) and resource attractiveness, and iii) traps may differ in their attractiveness profile. Example MGSurvE analyses are presented to demonstrate optimal trap placement for: i) an Aedes aegypti population in a suburban landscape in Queensland, Australia, and ii) an Anopheles gambiae population on the island of São Tomé, São Tomé and Príncipe. Further documentation and use examples are provided in project's documentation. MGSurvE is intended as a resource for both field and computational researchers interested in mosquito gene surveillance.
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Affiliation(s)
- Héctor M. Sánchez C.
- Divisions of Epidemiology and Biostatistics, University of California Berkeley, Berkeley, California, United States of America
| | - David L. Smith
- Institute for Health Metrics and Evaluation, University of Washington, Seattle, Washington, United States of America
- Department of Health Metrics Sciences, School of Medicine, University of Washington, Seattle, Washington, United States of America
| | - John M. Marshall
- Divisions of Epidemiology and Biostatistics, University of California Berkeley, Berkeley, California, United States of America
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Abossie A, Demissew A, Getachew H, Tsegaye A, Degefa T, Habtamu K, Zhong D, Wang X, Lee MC, Zhou G, King CL, Kazura JW, Yan G, Yewhalaw D. Higher outdoor mosquito density and Plasmodium infection rates in and around malaria index case households in low transmission settings of Ethiopia: Implications for vector control. Parasit Vectors 2024; 17:53. [PMID: 38321572 PMCID: PMC10848356 DOI: 10.1186/s13071-023-06088-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Accepted: 12/07/2023] [Indexed: 02/08/2024] Open
Abstract
BACKGROUND Understanding the clustering of infections for persistent malaria transmission is critical to determining how and where to target specific interventions. This study aimed to determine the density, blood meal sources and malaria transmission risk of anopheline vectors by targeting malaria index cases, their neighboring households and control villages in Arjo-Didessa, southwestern Ethiopia. METHODS An entomological study was conducted concurrently with a reactive case detection (RCD) study from November 2019 to October 2021 in Arjo Didessa and the surrounding vicinity, southwestern Ethiopia. Anopheline mosquitoes were collected indoors and outdoors in index case households and their surrounding households (neighboring households), as well as in control households, using pyrethrum spray cache (PSC) and U.S. Centers for Disease Control and Prevention (CDC) light traps. Adult mosquitoes were morphologically identified, and speciation in the Anopheles gambiae complex was done by PCR. Mosquito Plasmodium infections and host blood meal sources were detected by circumsporozoite protein enzyme-linked immunosorbent assay (CSP-ELISA) and cytochrome b-based blood meal PCR, respectively. RESULTS Among the 770 anopheline mosquitoes collected, An. gambiae sensu lato (A. gambiae s.l.) was the predominant species, accounting for 87.1% (n = 671/770) of the catch, followed by the Anopheles coustani complex and Anopheles pharoensis, which accounted for 12.6% (n = 97/770) and 0.26% (n = 2/770) of the catch, respectively. From the sub-samples of An. gambiae s.l.analyzed with PCR, An. arabiensis and Anopheles amharicus were identified. The overall mean density of mosquitoes was 1.26 mosquitoes per trap per night using the CDC light traps. Outdoor mosquito density was significantly higher than indoor mosquito density in the index and neighboring households (P = 0.0001). The human blood index (HBI) and bovine blood index (BBI) of An. arabiensis were 20.8% (n = 34/168) and 24.0% (n = 41/168), respectively. The overall Plasmodium sporozoite infection rate of anophelines (An. arabiensis and An. coustani complex) was 4.4% (n = 34/770). Sporozoites were detected indoors and outdoors in captured anopheline mosquitoes. Of these CSP-positive species for Pv-210, Pv-247 and Pf, 41.1% (n = 14/34) were captured outdoors. A significantly higher proportion of sporozoite-infected mosquitoes were caught in index case households (5.6%, n = 8/141) compared to control households (1.1%, n = 2/181) (P = 0.02), and in neighboring households (5.3%, n = 24/448) compared to control households (P = 0.01). CONCLUSIONS The findings of this study indicated that malaria index cases and their neighboring households had higher outdoor mosquito densities and Plasmodium infection rates. The study also highlighted a relatively higher outdoor mosquito density, which could increase the potential risk of outdoor malaria transmission and may play a role in residual malaria transmission. Thus, it is important to strengthen the implementation of vector control interventions, such as targeted indoor residual spraying, long-lasting insecticidal nets and other supplementary vector control measures such as larval source management and community engagement approaches. Furthermore, in low transmission settings, such as the Arjo Didessa Sugarcane Plantation, providing health education to local communities, enhanced environmental management and entomological surveillance, along with case detection and management by targeting of malaria index cases and their immediate neighboring households, could be important measures to control residual malaria transmission and achieve the targeted elimination goals.
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Affiliation(s)
- Ashenafi Abossie
- Department of Medical Laboratory Sciences, College of Medicine and Health Sciences, Arba Minch University, Arba Minch, Ethiopia.
- School of Medical Laboratory Sciences, Faculty of Health Sciences, Jimma University, Jimma, Ethiopia.
- Tropical and Infectious Diseases Research Center (TIDRC), Jimma University, Jimma, Ethiopia.
| | - Assalif Demissew
- Department of Medical Laboratory Sciences, College of Medicine and Health Sciences, Ambo University, Ambo, Ethiopia
- Aklilu Lemma Institute of Pathobiology, Addis Ababa University, Addis Ababa, Ethiopia
- Tropical and Infectious Diseases Research Center (TIDRC), Jimma University, Jimma, Ethiopia
| | - Hallelujah Getachew
- School of Medical Laboratory Sciences, Faculty of Health Sciences, Jimma University, Jimma, Ethiopia
- Department of Medical Laboratory Technology, Arba Minch College of Health Sciences, Arba Minch, Ethiopia
- Tropical and Infectious Diseases Research Center (TIDRC), Jimma University, Jimma, Ethiopia
| | - Arega Tsegaye
- School of Medical Laboratory Sciences, Faculty of Health Sciences, Jimma University, Jimma, Ethiopia
- Department of Biology, College of Natural Science, Jimma University, Jimma, Ethiopia
- Tropical and Infectious Diseases Research Center (TIDRC), Jimma University, Jimma, Ethiopia
| | - Teshome Degefa
- School of Medical Laboratory Sciences, Faculty of Health Sciences, Jimma University, Jimma, Ethiopia
- Tropical and Infectious Diseases Research Center (TIDRC), Jimma University, Jimma, Ethiopia
| | - Kassahun Habtamu
- Menelik II College of Health Sciences, Addis Ababa, Ethiopia
- Department of Microbial, Cellular and Molecular Biology, College of Natural Sciences, Addis Ababa University, Addis Ababa, Ethiopia
| | - Daibin Zhong
- Program in Public Health, University of California at Irvine, Irvine, CA, 92697, USA
| | - Xiaoming Wang
- Program in Public Health, University of California at Irvine, Irvine, CA, 92697, USA
| | - Ming-Chieh Lee
- Program in Public Health, University of California at Irvine, Irvine, CA, 92697, USA
| | - Guofa Zhou
- Program in Public Health, University of California at Irvine, Irvine, CA, 92697, USA
| | - Christopher L King
- Center for Global Health & Diseases, School of Medicine, Case Western Reserve University, Cleveland, 44106 OH, USA
| | - James W Kazura
- Center for Global Health & Diseases, School of Medicine, Case Western Reserve University, Cleveland, 44106 OH, USA
| | - Guiyun Yan
- Program in Public Health, University of California at Irvine, Irvine, CA, 92697, USA
| | - Delenasaw Yewhalaw
- School of Medical Laboratory Sciences, Faculty of Health Sciences, Jimma University, Jimma, Ethiopia
- Tropical and Infectious Diseases Research Center (TIDRC), Jimma University, Jimma, Ethiopia
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Werling K, Itoe MA, Shaw WR, Hien RD, Bazié BJ, Aminata F, Adams KL, Ouattara BS, Sanou M, Peng D, Dabiré RK, Da DF, Yerbanga RS, Diabaté A, Lefèvre T, Catteruccia F. Development of circulating isolates of Plasmodium falciparum is accelerated in Anopheles vectors with reduced reproductive output. PLoS Negl Trop Dis 2024; 18:e0011890. [PMID: 38206958 PMCID: PMC10807765 DOI: 10.1371/journal.pntd.0011890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Revised: 01/24/2024] [Accepted: 12/28/2023] [Indexed: 01/13/2024] Open
Abstract
Anopheles gambiae and its sibling species Anopheles coluzzii are the most efficient vectors of the malaria parasite Plasmodium falciparum. When females of these species feed on an infected human host, oogenesis and parasite development proceed concurrently, but interactions between these processes are not fully understood. Using multiple natural P. falciparum isolates from Burkina Faso, we show that in both vectors, impairing steroid hormone signaling to disrupt oogenesis leads to accelerated oocyst growth and in a manner that appears to depend on both parasite and mosquito genotype. Consistently, we find that egg numbers are negatively linked to oocyst size, a metric for the rate of oocyst development. Oocyst growth rates are also strongly accelerated in females that are in a pre-gravid state, i.e. that fail to develop eggs after an initial blood meal. Overall, these findings advance our understanding of mosquito-parasite interactions that influence P. falciparum development in malaria-endemic regions.
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Affiliation(s)
- Kristine Werling
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America
| | - Maurice A. Itoe
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America
| | - W. Robert Shaw
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
| | | | - Bali Jean Bazié
- Institut de Recherche en Sciences de la Santé/Centre Muraz, Bobo-Dioulasso, Burkina Faso
| | - Fofana Aminata
- Institut de Recherche en Sciences de la Santé/Centre Muraz, Bobo-Dioulasso, Burkina Faso
| | - Kelsey L. Adams
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America
| | | | - Mathias Sanou
- Institut de Recherche en Sciences de la Santé/Centre Muraz, Bobo-Dioulasso, Burkina Faso
| | - Duo Peng
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America
| | - Roch K. Dabiré
- Institut de Recherche en Sciences de la Santé/Centre Muraz, Bobo-Dioulasso, Burkina Faso
| | - Dari F. Da
- Institut de Recherche en Sciences de la Santé/Centre Muraz, Bobo-Dioulasso, Burkina Faso
| | | | - Abdoulaye Diabaté
- Institut de Recherche en Sciences de la Santé/Centre Muraz, Bobo-Dioulasso, Burkina Faso
| | - Thierry Lefèvre
- Institut de Recherche en Sciences de la Santé/Centre Muraz, Bobo-Dioulasso, Burkina Faso
- MIVEGEC, IRD, CNRS, University of Montpellier, Montpellier, France
| | - Flaminia Catteruccia
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
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Carrillo-Bustamante P, Costa G, Lampe L, Levashina EA. Evolutionary modelling indicates that mosquito metabolism shapes the life-history strategies of Plasmodium parasites. Nat Commun 2023; 14:8139. [PMID: 38097582 PMCID: PMC10721866 DOI: 10.1038/s41467-023-43810-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Accepted: 11/20/2023] [Indexed: 12/17/2023] Open
Abstract
Within-host survival and between-host transmission are key life-history traits of single-celled malaria parasites. Understanding the evolutionary forces that shape these traits is crucial to predict malaria epidemiology, drug resistance, and virulence. However, very little is known about how Plasmodium parasites adapt to their mosquito vectors. Here, we examine the evolution of the time Plasmodium parasites require to develop within the vector (extrinsic incubation period) with an individual-based model of malaria transmission that includes mosquito metabolism. Specifically, we model the metabolic cascade of resource allocation induced by blood-feeding, as well as the influence of multiple blood meals on parasite development. Our model predicts that successful vector-to-human transmission events are rare, and are caused by long-lived mosquitoes. Importantly, our results show that the life-history strategies of malaria parasites depend on the mosquito's metabolic status. In our model, additional resources provided by multiple blood meals lead to selection for parasites with slow or intermediate developmental time. These results challenge the current assumption that evolution favors fast developing parasites to maximize their chances to complete their within-mosquito life cycle. We propose that the long sporogonic cycle observed for Plasmodium is not a constraint but rather an adaptation to increase transmission potential.
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Affiliation(s)
| | - Giulia Costa
- Vector Biology Unit, Max Planck Institute for Infection Biology, 10117, Berlin, Germany
| | - Lena Lampe
- Vector Biology Unit, Max Planck Institute for Infection Biology, 10117, Berlin, Germany
- Physiology and Metabolism Laboratory, The Francis Crick Institute, NW11AT, London, UK
| | - Elena A Levashina
- Vector Biology Unit, Max Planck Institute for Infection Biology, 10117, Berlin, Germany.
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Benjamin-Chung J, Li H, Nguyen A, Heitmann GB, Bennett A, Ntuku H, Prach LM, Tambo M, Wu L, Drakeley C, Gosling R, Mumbengegwi D, Kleinschmidt I, Smith JL, Hubbard A, van der Laan M, Hsiang MS. Targeted malaria elimination interventions reduce Plasmodium falciparum infections up to 3 kilometers away. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2023:2023.09.19.23295806. [PMID: 37790419 PMCID: PMC10543053 DOI: 10.1101/2023.09.19.23295806] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 10/05/2023]
Abstract
Malaria elimination interventions in low-transmission settings aim to extinguish hot spots and prevent transmission to nearby areas. In malaria elimination settings, the World Health Organization recommends reactive, focal interventions targeted to the area near malaria cases shortly after they are detected. A key question is whether these interventions reduce transmission to nearby uninfected or asymptomatic individuals who did not receive interventions. Here, we measured direct effects (among intervention recipients) and spillover effects (among non-recipients) of reactive, focal interventions delivered within 500m of confirmed malaria index cases in a cluster-randomized trial in Namibia. The trial delivered malaria chemoprevention (artemether lumefantrine) and vector control (indoor residual spraying with Actellic) separately and in combination using a factorial design. We compared incidence, infection prevalence, and seroprevalence between study arms among intervention recipients (direct effects) and non-recipients (spillover effects) up to 3 km away from index cases. We calculated incremental cost-effectiveness ratios accounting for spillover effects. The combined chemoprevention and vector control intervention produced direct effects and spillover effects. In the primary analysis among non-recipients within 1 km from index cases, the combined intervention reduced malaria incidence by 43% (95% CI 20%, 59%). In secondary analyses among non-recipients 500m-3 km from interventions, the combined intervention reduced infection by 79% (6%, 95%) and seroprevalence 34% (20%, 45%). Accounting for spillover effects increased the cost-effectiveness of the combined intervention by 37%. Our findings provide the first evidence that targeting hot spots with combined chemoprevention and vector control interventions can indirectly benefit non-recipients up to 3 km away.
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Affiliation(s)
- Jade Benjamin-Chung
- Department of Epidemiology and Population Health, Stanford University, Stanford, United States
- Chan Zuckerberg Biohub, San Francisco, United States
| | - Haodong Li
- Division of Biostatistics, University of California, Berkeley
| | - Anna Nguyen
- Department of Epidemiology and Population Health, Stanford University, Stanford, United States
| | | | - Adam Bennett
- Malaria Elimination Initiative, Global Health Group, University of California, San Francisco (UCSF) , San Francisco, United States
- PATH, Seattle, United States
| | - Henry Ntuku
- Malaria Elimination Initiative, Global Health Group, University of California, San Francisco (UCSF) , San Francisco, United States
| | - Lisa M. Prach
- Malaria Elimination Initiative, Global Health Group, University of California, San Francisco (UCSF) , San Francisco, United States
| | - Munyaradzi Tambo
- Multidisciplinary Research Centre, University of Namibia, Windhoek, Namibia
| | - Lindsey Wu
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, UK
| | - Chris Drakeley
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, UK
| | - Roly Gosling
- Malaria Elimination Initiative, Global Health Group, University of California, San Francisco (UCSF) , San Francisco, United States
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
| | | | - Immo Kleinschmidt
- MRC International Statistics and Epidemiology Group, Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, UK
- Wits Research Institute for Malaria, Wits/SAMRC Collaborating Centre for Multi-Disciplinary Research on Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- Southern African Development Community Malaria Elimination Eight Secretariat, Windhoek, Namibia
| | - Jennifer L. Smith
- Malaria Elimination Initiative, Global Health Group, University of California, San Francisco (UCSF) , San Francisco, United States
| | - Alan Hubbard
- Division of Biostatistics, University of California, Berkeley
| | | | - Michelle S. Hsiang
- Chan Zuckerberg Biohub, San Francisco, United States
- Malaria Elimination Initiative, Global Health Group, University of California, San Francisco (UCSF) , San Francisco, United States
- Department of Epidemiology and Biostatistics, UCSF, San Francisco, United States
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Mwima R, Hui TYJ, Nanteza A, Burt A, Kayondo JK. Potential persistence mechanisms of the major Anopheles gambiae species complex malaria vectors in sub-Saharan Africa: a narrative review. Malar J 2023; 22:336. [PMID: 37936194 PMCID: PMC10631165 DOI: 10.1186/s12936-023-04775-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Accepted: 10/30/2023] [Indexed: 11/09/2023] Open
Abstract
The source of malaria vector populations that re-establish at the beginning of the rainy season is still unclear yet knowledge of mosquito behaviour is required to effectively institute control measures. Alternative hypotheses like aestivation, local refugia, migration between neighbouring sites, and long-distance migration (LDM) are stipulated to support mosquito persistence. This work assessed the malaria vector persistence dynamics and examined various studies done on vector survival via these hypotheses; aestivation, local refugia, local or long-distance migration across sub-Saharan Africa, explored a range of methods used, ecological parameters and highlighted the knowledge trends and gaps. The results about a particular persistence mechanism that supports the re-establishment of Anopheles gambiae, Anopheles coluzzii or Anopheles arabiensis in sub-Saharan Africa were not conclusive given that each method used had its limitations. For example, the Mark-Release-Recapture (MRR) method whose challenge is a low recapture rate that affects its accuracy, and the use of time series analysis through field collections whose challenge is the uncertainty about whether not finding mosquitoes during the dry season is a weakness of the conventional sampling methods used or because of hidden shelters. This, therefore, calls for further investigations emphasizing the use of ecological experiments under controlled conditions in the laboratory or semi-field, and genetic approaches, as they are known to complement each other. This review, therefore, unveils and assesses the uncertainties that influence the different malaria vector persistence mechanisms and provides recommendations for future studies.
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Affiliation(s)
- Rita Mwima
- Department of Entomology, Uganda Virus Research Institute (UVRI), Entebbe, Uganda
- Department of Biotechnical and Diagnostic Sciences, College of Veterinary Medicine, Animal Resources and Biosecurity (COVAB), Makerere University, Kampala, Uganda
| | - Tin-Yu J Hui
- Silwood Park Campus, Department of Life Sciences, Imperial College London, Ascot, UK
| | - Ann Nanteza
- Department of Biotechnical and Diagnostic Sciences, College of Veterinary Medicine, Animal Resources and Biosecurity (COVAB), Makerere University, Kampala, Uganda
| | - Austin Burt
- Silwood Park Campus, Department of Life Sciences, Imperial College London, Ascot, UK
| | - Jonathan K Kayondo
- Department of Entomology, Uganda Virus Research Institute (UVRI), Entebbe, Uganda.
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Ntabaliba W, Vavassori L, Stica C, Makungwa N, Odufuwa OG, Swai JK, Lekundayo R, Moore S. Life expectancy of Anopheles funestus is double that of Anopheles arabiensis in southeast Tanzania based on mark-release-recapture method. Sci Rep 2023; 13:15775. [PMID: 37737323 PMCID: PMC10516982 DOI: 10.1038/s41598-023-42761-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Accepted: 09/14/2023] [Indexed: 09/23/2023] Open
Abstract
Anopheles arabiensis and Anopheles funestus sensu stricto mosquitoes are major East African malaria vectors. Understanding their dispersal and population structure is critical for developing effective malaria control tools. Three mark-release-recapture (MRR) experiments were conducted for 51 nights to assess daily survival and flight range of An. arabiensis and An. funestus mosquitoes in south-eastern, Tanzania. Mosquitoes were marked with a fluorescent dye as they emerged from breeding sites via a self-marking device. Mosquitoes were collected indoors and outdoors using human landing catches (HLC) and Centers for Disease Control and Prevention light traps (CDC-LT). In total, 4210 An. arabiensis and An. funestus were collected with 316 (7.5%) marked and recaptured (MR). Daily mean MR was 6.8, standard deviation (SD ± 7.6) for An. arabiensis and 8.9 (SD ± 8.3) for An. funestus. Probability of daily survival was 0.76 for An. arabiensis and 0.86 for An. funestus translating into average life expectancy of 3.6 days for An. arabiensis and 6.5 days for An. funestus. Dispersal distance was 654 m for An. arabiensis and 510 m for An. funestus. An. funestus life expectancy was substantially longer than that of An. arabiensis. The MRR method described here could be routinely utilized when evaluating the impact of new vector control tools on mosquito survival.
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Affiliation(s)
- Watson Ntabaliba
- Vector Control Product Testing Unit (VCPTU), Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania.
| | - Laura Vavassori
- Vector Biology Unit, Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Kreuzstrasse 2, 4123, Allschwil, Switzerland
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland
| | - Caleb Stica
- Queensland University of Technology, Brisbane, Australia
| | - Noel Makungwa
- Vector Control Product Testing Unit (VCPTU), Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Olukayode G Odufuwa
- Vector Control Product Testing Unit (VCPTU), Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
- Vector Biology Unit, Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Kreuzstrasse 2, 4123, Allschwil, Switzerland
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland
- MRC International Statistics and Epidemiology Group, Faculty of Epidemiology and Population Health London School of Hygiene and Tropical Medicine, London, UK
| | - Johnson Kyeba Swai
- Vector Control Product Testing Unit (VCPTU), Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
- Vector Biology Unit, Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Kreuzstrasse 2, 4123, Allschwil, Switzerland
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland
| | - Ruth Lekundayo
- Vector Control Product Testing Unit (VCPTU), Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Sarah Moore
- Vector Control Product Testing Unit (VCPTU), Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
- Vector Biology Unit, Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Kreuzstrasse 2, 4123, Allschwil, Switzerland
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland
- Nelson Mandela African Institute of Science and Technology, Tengeru, Arusha, Tanzania
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8
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Hollingsworth BD, Grubaugh ND, Lazzaro BP, Murdock CC. Leveraging insect-specific viruses to elucidate mosquito population structure and dynamics. PLoS Pathog 2023; 19:e1011588. [PMID: 37651317 PMCID: PMC10470969 DOI: 10.1371/journal.ppat.1011588] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/02/2023] Open
Abstract
Several aspects of mosquito ecology that are important for vectored disease transmission and control have been difficult to measure at epidemiologically important scales in the field. In particular, the ability to describe mosquito population structure and movement rates has been hindered by difficulty in quantifying fine-scale genetic variation among populations. The mosquito virome represents a possible avenue for quantifying population structure and movement rates across multiple spatial scales. Mosquito viromes contain a diversity of viruses, including several insect-specific viruses (ISVs) and "core" viruses that have high prevalence across populations. To date, virome studies have focused on viral discovery and have only recently begun examining viral ecology. While nonpathogenic ISVs may be of little public health relevance themselves, they provide a possible route for quantifying mosquito population structure and dynamics. For example, vertically transmitted viruses could behave as a rapidly evolving extension of the host's genome. It should be possible to apply established analytical methods to appropriate viral phylogenies and incidence data to generate novel approaches for estimating mosquito population structure and dispersal over epidemiologically relevant timescales. By studying the virome through the lens of spatial and genomic epidemiology, it may be possible to investigate otherwise cryptic aspects of mosquito ecology. A better understanding of mosquito population structure and dynamics are key for understanding mosquito-borne disease ecology and methods based on ISVs could provide a powerful tool for informing mosquito control programs.
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Affiliation(s)
- Brandon D Hollingsworth
- Department of Entomology, Cornell University, Ithaca, New York, United States of America
- Cornell Institute for Host Microbe Interaction and Disease, Cornell University, Ithaca, New York, United States of America
| | - Nathan D Grubaugh
- Yale School of Public Health, New Haven, Connecticut, United States of America
- Yale University, New Haven, Connecticut, United States of America
| | - Brian P Lazzaro
- Department of Entomology, Cornell University, Ithaca, New York, United States of America
- Cornell Institute for Host Microbe Interaction and Disease, Cornell University, Ithaca, New York, United States of America
| | - Courtney C Murdock
- Department of Entomology, Cornell University, Ithaca, New York, United States of America
- Cornell Institute for Host Microbe Interaction and Disease, Cornell University, Ithaca, New York, United States of America
- Northeast Regional Center for Excellence in Vector-borne Diseases, Cornell University, Ithaca, New York, United States of America
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Sánchez C. HM, Smith DL, Marshall JM. MGSurvE: A framework to optimize trap placement for genetic surveillance of mosquito population. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.26.546301. [PMID: 37425729 PMCID: PMC10327167 DOI: 10.1101/2023.06.26.546301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
Genetic surveillance of mosquito populations is becoming increasingly relevant as genetics-based mosquito control strategies advance from laboratory to field testing. Especially applicable are mosquito gene drive projects, the potential scale of which leads monitoring to be a significant cost driver. For these projects, monitoring will be required to detect unintended spread of gene drive mosquitoes beyond field sites, and the emergence of alternative alleles, such as drive-resistant alleles or non-functional effector genes, within intervention sites. This entails the need to distribute mosquito traps efficiently such that an allele of interest is detected as quickly as possible - ideally when remediation is still viable. Additionally, insecticide-based tools such as bednets are compromised by insecticide-resistance alleles for which there is also a need to detect as quickly as possible. To this end, we present MGSurvE (Mosquito Gene SurveillancE): a computational framework that optimizes trap placement for genetic surveillance of mosquito populations such that the time to detection of an allele of interest is minimized. A key strength of MGSurvE is that it allows important biological features of mosquitoes and the landscapes they inhabit to be accounted for, namely: i) resources required by mosquitoes (e.g., food sources and aquatic breeding sites) can be explicitly distributed through a landscape, ii) movement of mosquitoes may depend on their sex, the current state of their gonotrophic cycle (if female) and resource attractiveness, and iii) traps may differ in their attractiveness profile. Example MGSurvE analyses are presented to demonstrate optimal trap placement for: i) an Aedes aegypti population in a suburban landscape in Queensland, Australia, and ii) an Anopheles gambiae population on the island of São Tomé, São Tomé and Príncipe. Further documentation and use examples are provided in project's documentation. MGSurvE is freely available as an open-source Python package on pypi (https://pypi.org/project/MGSurvE/). It is intended as a resource for both field and computational researchers interested in mosquito gene surveillance.
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Affiliation(s)
- Héctor M. Sánchez C.
- Divisions of Epidemiology and Biostatistics, School of Public Health, University of California, Berkeley, California, United States of America
| | - David L. Smith
- Institute for Health Metrics and Evaluation, University of Washington, Seattle, WA, USA
- Department of Health Metrics Sciences, School of Medicine, University of Washington, Seattle, WA, USA
| | - John M. Marshall
- Divisions of Epidemiology and Biostatistics, School of Public Health, University of California, Berkeley, California, United States of America
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10
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Smith CCR, Tittes S, Ralph PL, Kern AD. Dispersal inference from population genetic variation using a convolutional neural network. Genetics 2023; 224:iyad068. [PMID: 37052957 PMCID: PMC10213498 DOI: 10.1093/genetics/iyad068] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 02/08/2023] [Accepted: 04/07/2023] [Indexed: 04/14/2023] Open
Abstract
The geographic nature of biological dispersal shapes patterns of genetic variation over landscapes, making it possible to infer properties of dispersal from genetic variation data. Here, we present an inference tool that uses geographically distributed genotype data in combination with a convolutional neural network to estimate a critical population parameter: the mean per-generation dispersal distance. Using extensive simulation, we show that our deep learning approach is competitive with or outperforms state-of-the-art methods, particularly at small sample sizes. In addition, we evaluate varying nuisance parameters during training-including population density, demographic history, habitat size, and sampling area-and show that this strategy is effective for estimating dispersal distance when other model parameters are unknown. Whereas competing methods depend on information about local population density or accurate inference of identity-by-descent tracts, our method uses only single-nucleotide-polymorphism data and the spatial scale of sampling as input. Strikingly, and unlike other methods, our method does not use the geographic coordinates of the genotyped individuals. These features make our method, which we call "disperseNN," a potentially valuable new tool for estimating dispersal distance in nonmodel systems with whole genome data or reduced representation data. We apply disperseNN to 12 different species with publicly available data, yielding reasonable estimates for most species. Importantly, our method estimated consistently larger dispersal distances than mark-recapture calculations in the same species, which may be due to the limited geographic sampling area covered by some mark-recapture studies. Thus genetic tools like ours complement direct methods for improving our understanding of dispersal.
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Affiliation(s)
- Chris C R Smith
- Institute of Ecology and Evolution, University of Oregon, Eugene, OR 97403, USA
| | - Silas Tittes
- Institute of Ecology and Evolution, University of Oregon, Eugene, OR 97403, USA
| | - Peter L Ralph
- Institute of Ecology and Evolution, University of Oregon, Eugene, OR 97403, USA
| | - Andrew D Kern
- Institute of Ecology and Evolution, University of Oregon, Eugene, OR 97403, USA
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11
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Tan MH, Shim H, Chan YB, Day KP. Unravelling var complexity: Relationship between DBLα types and var genes in Plasmodium falciparum. FRONTIERS IN PARASITOLOGY 2023; 1. [PMID: 36998722 PMCID: PMC10060044 DOI: 10.3389/fpara.2022.1006341] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The enormous diversity and complexity of var genes that diversify rapidly by recombination has led to the exclusion of assembly of these genes from major genome initiatives (e.g., Pf6). A scalable solution in epidemiological surveillance of var genes is to use a small ‘tag’ region encoding the immunogenic DBLα domain as a marker to estimate var diversity. As var genes diversify by recombination, it is not clear the extent to which the same tag can appear in multiple var genes. This relationship between marker and gene has not been investigated in natural populations. Analyses of in vitro recombination within and between var genes have suggested that this relationship would not be exclusive. Using a dataset of publicly-available assembled var sequences, we test this hypothesis by studying DBLα-var relationships for four study sites in four countries: Pursat (Cambodia) and Mae Sot (Thailand), representing low malaria transmission, and Navrongo (Ghana) and Chikwawa (Malawi), representing high malaria transmission. In all study sites, DBLα-var relationships were shown to be predominantly 1-to-1, followed by a second largest proportion of 1-to-2 DBLα-var relationships. This finding indicates that DBLα tags can be used to estimate not just DBLα diversity but var gene diversity when applied in a local endemic area. Epidemiological applications of this result are discussed.
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Affiliation(s)
- Mun Hua Tan
- Department of Microbiology and Immunology, The University of Melbourne, Bio21 Institute, Melbourne, VIC, Australia
| | - Heejung Shim
- School of Mathematics and Statistics/Melbourne Integrative Genomics, The University of Melbourne, Melbourne, VIC, Australia
| | - Yao-ban Chan
- School of Mathematics and Statistics/Melbourne Integrative Genomics, The University of Melbourne, Melbourne, VIC, Australia
| | - Karen P. Day
- Department of Microbiology and Immunology, The University of Melbourne, Bio21 Institute, Melbourne, VIC, Australia
- CORRESPONDENCE Karen P. Day,
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12
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Faiman R, Yaro AS, Dao A, Sanogo ZL, Diallo M, Samake D, Yossi O, Veru LM, Graber LC, Conte AR, Kouam C, Krajacich BJ, Lehmann T. Isotopic evidence that aestivation allows malaria mosquitoes to persist through the dry season in the Sahel. Nat Ecol Evol 2022; 6:1687-1699. [PMID: 36216903 DOI: 10.1038/s41559-022-01886-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 08/11/2022] [Indexed: 11/09/2022]
Abstract
Data suggest that the malaria vector mosquito Anopheles coluzzii persists during the dry season in the Sahel through a dormancy mechanism known as aestivation; however, the contribution of aestivation compared with alternative strategies such as migration is unknown. Here we marked larval Anopheles mosquitoes in two Sahelian villages in Mali using deuterium (2H) to assess the contribution of aestivation to persistence of mosquitoes through the seven-month dry season. After an initial enrichment period, 33% of An. coluzzii mosquitoes were strongly marked. Seven months following enrichment, multiple analysis methods supported the ongoing presence of marked mosquitoes, compatible with the prediction that the fraction of marked mosquitoes should remain stable throughout the dry season if local aestivation is occurring. The results suggest that aestivation is a major persistence mechanism of An. coluzzii in the Sahel, contributing at least 20% of the adults at the onset of rains. This persistence strategy could influence mosquito control and malaria elimination campaigns.
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Affiliation(s)
- Roy Faiman
- Laboratory of Malaria and Vector Research, NIAID, NIH, Rockville, MD, USA.
| | - Alpha S Yaro
- Malaria Research and Training Center (MRTC)/Faculty of Medicine, Pharmacy and Odonto-stomatology, University of Sciences, Techniques and Technologies of Bamako, Bamako, Mali
| | - Adama Dao
- Malaria Research and Training Center (MRTC)/Faculty of Medicine, Pharmacy and Odonto-stomatology, University of Sciences, Techniques and Technologies of Bamako, Bamako, Mali
| | - Zana L Sanogo
- Malaria Research and Training Center (MRTC)/Faculty of Medicine, Pharmacy and Odonto-stomatology, University of Sciences, Techniques and Technologies of Bamako, Bamako, Mali
| | - Moussa Diallo
- Malaria Research and Training Center (MRTC)/Faculty of Medicine, Pharmacy and Odonto-stomatology, University of Sciences, Techniques and Technologies of Bamako, Bamako, Mali
| | - Djibril Samake
- Malaria Research and Training Center (MRTC)/Faculty of Medicine, Pharmacy and Odonto-stomatology, University of Sciences, Techniques and Technologies of Bamako, Bamako, Mali
| | - Ousmane Yossi
- Malaria Research and Training Center (MRTC)/Faculty of Medicine, Pharmacy and Odonto-stomatology, University of Sciences, Techniques and Technologies of Bamako, Bamako, Mali
| | - Laura M Veru
- Laboratory of Malaria and Vector Research, NIAID, NIH, Rockville, MD, USA
| | - Leland C Graber
- Laboratory of Malaria and Vector Research, NIAID, NIH, Rockville, MD, USA
| | - Abigail R Conte
- Laboratory of Malaria and Vector Research, NIAID, NIH, Rockville, MD, USA
| | - Cedric Kouam
- Laboratory of Malaria and Vector Research, NIAID, NIH, Rockville, MD, USA
| | | | - Tovi Lehmann
- Laboratory of Malaria and Vector Research, NIAID, NIH, Rockville, MD, USA
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13
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Yaro AS, Linton YM, Dao A, Diallo M, Sanogo ZL, Samake D, Ousmane Y, Kouam C, Krajacich BJ, Faiman R, Bamou R, Woo J, Chapman JW, Reynolds DR, Lehmann T. Diversity, composition, altitude, and seasonality of high-altitude windborne migrating mosquitoes in the Sahel: Implications for disease transmission. FRONTIERS IN EPIDEMIOLOGY 2022; 2:1001782. [PMID: 38455321 PMCID: PMC10910920 DOI: 10.3389/fepid.2022.1001782] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/24/2022] [Accepted: 09/16/2022] [Indexed: 03/09/2024]
Abstract
Recent studies have reported Anopheles mosquitoes captured at high-altitude (40-290 m above ground) in the Sahel. Here, we describe this migration modality across genera and species of African Culicidae and examine its implications for disease transmission and control. As well as Anopheles, six other genera-Culex, Aedes, Mansonia, Mimomyia, Lutzia, and Eretmapodites comprised 90% of the 2,340 mosquitoes captured at altitude. Of the 50 molecularly confirmed species (N = 2,107), 33 species represented by multiple specimens were conservatively considered high-altitude windborne migrants, suggesting it is a common migration modality in mosquitoes (31-47% of the known species in Mali), and especially in Culex (45-59%). Overall species abundance varied between 2 and 710 specimens/species (in Ae. vittatus and Cx. perexiguus, respectively). At altitude, females outnumbered males 6:1, and 93% of the females have taken at least one blood meal on a vertebrate host prior to their departure. Most taxa were more common at higher sampling altitudes, indicating that total abundance and diversity are underestimated. High-altitude flight activity was concentrated between June and November coinciding with availability of surface waters and peak disease transmission by mosquitoes. These hallmarks of windborne mosquito migration bolster their role as carriers of mosquito-borne pathogens (MBPs). Screening 921 mosquitoes using pan-Plasmodium assays revealed that thoracic infection rate in these high-altitude migrants was 2.4%, providing a proof of concept that vertebrate pathogens are transported by windborne mosquitoes at altitude. Fourteen of the 33 windborne mosquito species had been reported as vectors to 25 MBPs in West Africa, which represent 32% of the MBPs known in that region and include those that inflict the heaviest burden on human and animal health, such as malaria, yellow fever, dengue, and Rift Valley fever. We highlight five arboviruses that are most likely affected by windborne mosquitoes in West Africa: Rift Valley fever, O'nyong'nyong, Ngari, Pangola, and Ndumu. We conclude that the study of windborne spread of diseases by migrating insects and the development of surveillance to map the sources, routes, and destinations of vectors and pathogens is key to understand, predict, and mitigate existing and new threats of public health.
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Affiliation(s)
- Alpha Seydou Yaro
- Malaria Research and Training Center (MRTC), Faculty of Medicine, Pharmacy and Odonto-Stomatology, Bamako, Mali
| | - Yvonne-Marie Linton
- Walter Reed Biosystematics Unit, Smithsonian Institution Museum Support Center, Suitland, MD, United States
- Department of Entomology, Smithsonian Institution, National Museum of Natural History, Washington, DC, United States
- One Health Branch, Walter Reed Army Institute of Research, Silver Spring, MD, United States
| | - Adama Dao
- Malaria Research and Training Center (MRTC), Faculty of Medicine, Pharmacy and Odonto-Stomatology, Bamako, Mali
| | - Moussa Diallo
- Malaria Research and Training Center (MRTC), Faculty of Medicine, Pharmacy and Odonto-Stomatology, Bamako, Mali
| | - Zana L. Sanogo
- Malaria Research and Training Center (MRTC), Faculty of Medicine, Pharmacy and Odonto-Stomatology, Bamako, Mali
| | - Djibril Samake
- Malaria Research and Training Center (MRTC), Faculty of Medicine, Pharmacy and Odonto-Stomatology, Bamako, Mali
| | - Yossi Ousmane
- Malaria Research and Training Center (MRTC), Faculty of Medicine, Pharmacy and Odonto-Stomatology, Bamako, Mali
| | - Cedric Kouam
- Laboratory of Malaria and Vector Research, NIAID, NIH, Rockville, MD, United States
| | | | - Roy Faiman
- Laboratory of Malaria and Vector Research, NIAID, NIH, Rockville, MD, United States
| | - Roland Bamou
- Laboratory of Malaria and Vector Research, NIAID, NIH, Rockville, MD, United States
| | - Joshua Woo
- Krieger School of Arts and Sciences, Johns Hopkins University, Baltimore, MD, United States
| | - Jason W. Chapman
- Centre for Ecology and Conservation, and Environment and Sustainability Institute, University of Exeter, Penryn, United Kingdom
- Department of Entomology, College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Don R. Reynolds
- Natural Resources Institute, University of Greenwich, Chatham, United Kingdom
- Rothamsted Research, Harpenden, United Kingdom
| | - Tovi Lehmann
- Laboratory of Malaria and Vector Research, NIAID, NIH, Rockville, MD, United States
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14
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Reply to Wagman et al.: Data-driven assessments should establish the landscape of what is "within reach" of malaria transmission control. Proc Natl Acad Sci U S A 2022; 119:e2211931119. [PMID: 36095179 PMCID: PMC9499576 DOI: 10.1073/pnas.2211931119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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15
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Zimmerman RH, Galardo AKR, Lounibos LP, Galardo C, Bahar AK, van Santen E. Vectorial capacities for malaria in eastern Amazonian Brazil depend on village, vector species, season, and parasite species. Malar J 2022; 21:237. [PMID: 35974410 PMCID: PMC9382821 DOI: 10.1186/s12936-022-04255-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 07/29/2022] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND The vector species in the Amazon River Basin are regionally and locally diverse, which makes it imperative to understand and compare their roles in malaria transmission to help select appropriate methods of intervention and evaluation. The major aim of this study was to measure the vectorial capacity of five Anopheles species in three neighbouring villages, for two Plasmodium parasite species affecting humans. METHODS From 32 consecutive months of sampling in three villages, 1.5-7.0 km apart, on the Matapi River, Amapá State, Brazil, vectorial capacities (C) were estimated as time series for An. darlingi, An. marajoara, An. nuneztovari, An. triannulatus, and An. intermedius. Monthly parity measurements for each vector species were used to estimate daily survivorship and compared to estimates of survivorship from mark-release-recapture experiments. Gonotrophic cycle lengths were estimated through a time-series analysis of parity data, and durations of sporogony at study site temperatures for the two malaria parasite species were estimated from previous literature. RESULTS The absolute abundances of five vector species were strongly tracked by the spatial variation in C among villages. Temporally, C varied between wet and dry seasons, with An. darlingi, An. marajoara and An. triannulatus exhibiting higher C in the dry season from August to December, and An. nuneztovari its highest C early in the rainy season in January and February. Anopheles intermedius exhibited higher C in the rainy season from April to June than in the dry season. Significant differences in overall survival for each independent variable, and a significant difference in C between wet and dry seasons, among villages, and among vector species for both Plasmodium falciparum and Plasmodium vivax. A generalized linear mixed model (GLMM) analysis by village showed significant effects of vector species on C in only one village, but significant effects of parasite species in all three. Although the GLMM analysis detected no significant parasite x vector species interaction effects on C, effects on C of spline regressions of C dynamics x vector species interactions were significant in all villages. CONCLUSIONS These detailed analyses of entomological and parasitological variables revealed hidden complexities of malaria epidemiology at local scales in neighbouring riverine villages of the Amazon Region.
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Affiliation(s)
- Robert H. Zimmerman
- Florida Medical Entomology Laboratory, University of Florida/IFAS, 200 9th Street SE, Vero Beach, FL 32962 USA
| | - Allan K. R. Galardo
- Laboratório de Entomologia Médica, Instituto de Pesquisas Científicas E Tecnológicas Do Estado de Amapá-IEPA, Campus do IEPA da Fazendinha-CEP, Macapá, 68912-250 Brazil
| | - L Philip Lounibos
- Florida Medical Entomology Laboratory, University of Florida/IFAS, 200 9th Street SE, Vero Beach, FL 32962 USA
| | - Clicia Galardo
- Laboratório de Entomologia Médica, Instituto de Pesquisas Científicas E Tecnológicas Do Estado de Amapá-IEPA, Campus do IEPA da Fazendinha-CEP, Macapá, 68912-250 Brazil
| | | | - Edzard van Santen
- Agronomy Department and Statistical Consulting Unit, University of Florida/IFAS, Gainesville, FL 32611 USA
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16
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Gamez S, Chaverra-Rodriguez D, Buchman A, Kandul NP, Mendez-Sanchez SC, Bennett JB, Sánchez C HM, Yang T, Antoshechkin I, Duque JE, Papathanos PA, Marshall JM, Akbari OS. Exploiting a Y chromosome-linked Cas9 for sex selection and gene drive. Nat Commun 2021; 12:7202. [PMID: 34893590 PMCID: PMC8664916 DOI: 10.1038/s41467-021-27333-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Accepted: 11/03/2021] [Indexed: 02/06/2023] Open
Abstract
CRISPR-based genetic engineering tools aimed to bias sex ratios, or drive effector genes into animal populations, often integrate the transgenes into autosomal chromosomes. However, in species with heterogametic sex chromsomes (e.g. XY, ZW), sex linkage of endonucleases could be beneficial to drive the expression in a sex-specific manner to produce genetic sexing systems, sex ratio distorters, or even sex-specific gene drives, for example. To explore this possibility, here we develop a transgenic line of Drosophila melanogaster expressing Cas9 from the Y chromosome. We functionally characterize the utility of this strain for both sex selection and gene drive finding it to be quite effective. To explore its utility for population control, we built mathematical models illustrating its dynamics as compared to other state-of-the-art systems designed for both population modification and suppression. Taken together, our results contribute to the development of current CRISPR genetic control tools and demonstrate the utility of using sex-linked Cas9 strains for genetic control of animals.
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Affiliation(s)
- Stephanie Gamez
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, 92093, USA
- Agragene Inc., San Diego, CA, 92121, USA
| | - Duverney Chaverra-Rodriguez
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Anna Buchman
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, 92093, USA
- Verily Life Sciences, South San Francisco, CA, 94080, USA
| | - Nikolay P Kandul
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Stelia C Mendez-Sanchez
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, 92093, USA
- Group for Research in Biochemistry and Microbiology (Grupo de Investigación en Bioquímica Y Microbiología-GIBIM), School of Chemistry, Universidad Industrial de Santander, Bucaramanga, Colombia
| | - Jared B Bennett
- Biophysics Graduate Group, University of California, Berkeley, CA, 94720, USA
- Divisions of Epidemiology & Biostatistics, School of Public Health, University of California, Berkeley, CA, 94720, USA
| | - Héctor M Sánchez C
- Divisions of Epidemiology & Biostatistics, School of Public Health, University of California, Berkeley, CA, 94720, USA
| | - Ting Yang
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Igor Antoshechkin
- Division of Biology and Biological Engineering (BBE), California Institute of Technology, Pasadena, CA, 91125, USA
| | - Jonny E Duque
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, 92093, USA
- Centro de Investigaciones en Enfermedades Tropicales - CINTROP, Facultad de Salud, Escuela de Medicina, Departamento de Ciencias Básicas, Universidad Industrial de Santander, Piedecuesta, Santander, Colombia
| | - Philippos A Papathanos
- Department of Entomology, Robert H. Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, 7610001, Israel
| | - John M Marshall
- Divisions of Epidemiology & Biostatistics, School of Public Health, University of California, Berkeley, CA, 94720, USA
- Innovative Genomics Institute, University of California, Berkeley, CA, 94720, USA
| | - Omar S Akbari
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, 92093, USA.
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17
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Evaluation of Mosquito Attractant Candidates Using a High-Throughput Screening System for Aedes aegypti (L.) , Culex quinquefasciatus Say. and Anopheles minimus Theobald (Diptera: Culicidae). INSECTS 2021; 12:insects12060528. [PMID: 34204117 PMCID: PMC8226803 DOI: 10.3390/insects12060528] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 05/13/2021] [Accepted: 06/04/2021] [Indexed: 11/17/2022]
Abstract
Several types of olfactometers have been used to evaluate mosquito responses to agents that mimic natural volatiles that repel or attract. The Y-tube olfactometer has been widely used to study repellents and attractants, while the high-throughput screening system assay has only been used to study repellents. Whether the high-throughput screening system assay is suitable for evaluating attractants is unknown. We evaluated the responses to four lactic-acid-based mixtures and two non-lactic-acid-based chemical lure candidates using the high-throughput screening system (HITSS) for three mosquito species (laboratory strains and field populations of both Aedes aegypti (L.) and Culex quinquefasciatus Say.; laboratory strain of Anopheles minimus Theobald) under laboratory-controlled conditions. HITSS assay results showed that KU-lure #1 elicited the greatest percent attraction for pyrethroid-resistant and -susceptible Ae. aegypti. KU-lure #6 elicited the strongest attractive response for pyrethroid-susceptible and -resistant Cx. quinquefasciatus and pyrethroid-susceptible An. minimus. The response to the lures from each species was independent of the pyrethroid susceptibility status (Ae. aegypti, p = 0.825; Cx. quinquefasciatus, p = 0.056). However, a significant difference in attraction to KU-lure #6 was observed between diurnal and nocturnal mosquitoes (Cx. quinquefasciatus vs. Ae. aegypti, p = 0.014; An. minimus vs. Ae. aegypti, p = 0.001). The laboratory-level HITSS assay effectively selects potential lure candidates. Because the host-seeking behavior differs between mosquito species, further studies are needed to develop species-specific attractants. Additional studies in semi-field screen houses using commercial traps are necessary to evaluate the accuracy of these laboratory assay results.
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18
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Faiman R, Krajacich BJ, Graber L, Dao A, Yaro AS, Yossi O, Sanogo ZL, Diallo M, Samaké D, Sylla D, Coulibaly M, Kone S, Goita S, Coulibaly MB, Muratova O, McCormack A, Gonçalves BP, Hume J, Duffy P, Lehmann T. A novel fluorescence and DNA combination for versatile, long-term marking of mosquitoes. Methods Ecol Evol 2021; 12:1008-1016. [PMID: 34249305 PMCID: PMC8252004 DOI: 10.1111/2041-210x.13592] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Accepted: 02/19/2021] [Indexed: 11/29/2022]
Abstract
Current mark-release-recapture methodologies are limited in their ability to address complex problems in vector biology, such as studying multiple groups overlapping in space and time. Additionally, limited mark retention, reduced post-marking survival and the large effort in marking, collection and recapture all complicate effective insect tracking.We have developed and evaluated a marking method using a fluorescent dye (SmartWater®) combined with synthetic DNA tags to informatively and efficiently mark adult mosquitoes using an airbrush pump and nebulizer. Using a handheld UV flashlight, the fluorescent marking enabled quick and simple initial detection of recaptures in a field-ready and non-destructive approach that when combined with an extraction-free PCR on individual mosquito legs provides potentially unlimited marking information.This marking, first tested in the laboratory with Anopheles gambiae s.l. mosquitoes, did not affect survival (median ages 24-28 days, p-adj > 0.25), oviposition (median eggs/female of 28.8, 32.5, 33.3 for water, green, red dyes, respectively, p-adj > 0.44) or Plasmodium competence (mean oocysts 5.56-10.6, p-adj > 0.95). DNA and fluorescence had 100% retention up to 3 weeks (longest time point tested) with high intensity, indicating marks would persist longer.We describe a novel, simple, no/low-impact and long-lasting marking method that allows separation of multiple insect subpopulations by combining unlimited length and sequence variation in the synthetic DNA tags. This method can be readily deployed in the field for marking multiple groups of mosquitoes or other insects.
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Affiliation(s)
- Roy Faiman
- Laboratory of Malaria and Vector ResearchNIAIDNIHRockvilleMDUSA
| | | | - Leland Graber
- Laboratory of Malaria and Vector ResearchNIAIDNIHRockvilleMDUSA
| | - Adama Dao
- Malaria Research and Training Center (MRTC)/Faculty of Medicine, Pharmacy and Odonto‐stomatologyUniversity of Sciences, Techniques and TechnologiesBamakoMali
| | - Alpha Seydou Yaro
- Malaria Research and Training Center (MRTC)/Faculty of Medicine, Pharmacy and Odonto‐stomatologyUniversity of Sciences, Techniques and TechnologiesBamakoMali
| | - Ousmane Yossi
- Malaria Research and Training Center (MRTC)/Faculty of Medicine, Pharmacy and Odonto‐stomatologyUniversity of Sciences, Techniques and TechnologiesBamakoMali
| | - Zana Lamissa Sanogo
- Malaria Research and Training Center (MRTC)/Faculty of Medicine, Pharmacy and Odonto‐stomatologyUniversity of Sciences, Techniques and TechnologiesBamakoMali
| | - Moussa Diallo
- Malaria Research and Training Center (MRTC)/Faculty of Medicine, Pharmacy and Odonto‐stomatologyUniversity of Sciences, Techniques and TechnologiesBamakoMali
| | - Djibril Samaké
- Malaria Research and Training Center (MRTC)/Faculty of Medicine, Pharmacy and Odonto‐stomatologyUniversity of Sciences, Techniques and TechnologiesBamakoMali
| | - Daman Sylla
- Malaria Research and Training Center (MRTC)/Faculty of Medicine, Pharmacy and Odonto‐stomatologyUniversity of Sciences, Techniques and TechnologiesBamakoMali
| | - Moribo Coulibaly
- Malaria Research and Training Center (MRTC)/Faculty of Medicine, Pharmacy and Odonto‐stomatologyUniversity of Sciences, Techniques and TechnologiesBamakoMali
| | - Salif Kone
- Malaria Research and Training Center (MRTC)/Faculty of Medicine, Pharmacy and Odonto‐stomatologyUniversity of Sciences, Techniques and TechnologiesBamakoMali
| | - Sekou Goita
- Malaria Research and Training Center (MRTC)/Faculty of Medicine, Pharmacy and Odonto‐stomatologyUniversity of Sciences, Techniques and TechnologiesBamakoMali
| | - Mamadou B. Coulibaly
- Malaria Research and Training Center (MRTC)/Faculty of Medicine, Pharmacy and Odonto‐stomatologyUniversity of Sciences, Techniques and TechnologiesBamakoMali
| | - Olga Muratova
- Laboratory of Malaria Immunology and VaccinologyNational Institute of Allergy and Infectious DiseasesNational Institutes of HealthBethesdaMDUSA
| | - Ashley McCormack
- Laboratory of Malaria Immunology and VaccinologyNational Institute of Allergy and Infectious DiseasesNational Institutes of HealthBethesdaMDUSA
| | - Bronner P. Gonçalves
- Laboratory of Malaria Immunology and VaccinologyNational Institute of Allergy and Infectious DiseasesNational Institutes of HealthBethesdaMDUSA
| | - Jennifer Hume
- Laboratory of Malaria Immunology and VaccinologyNational Institute of Allergy and Infectious DiseasesNational Institutes of HealthBethesdaMDUSA
| | - Patrick Duffy
- Laboratory of Malaria Immunology and VaccinologyNational Institute of Allergy and Infectious DiseasesNational Institutes of HealthBethesdaMDUSA
| | - Tovi Lehmann
- Laboratory of Malaria and Vector ResearchNIAIDNIHRockvilleMDUSA
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19
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Hast MA, Stevenson JC, Muleba M, Chaponda M, Kabuya JB, Mulenga M, Shields T, Moss WJ, Norris DE, For The Southern And Central Africa International Centers Of Excellence In Malaria Research. The Impact of Three Years of Targeted Indoor Residual Spraying with Pirimiphos-Methyl on Household Vector Abundance in a High Malaria Transmission Area of Northern Zambia. Am J Trop Med Hyg 2020; 104:683-694. [PMID: 33350376 PMCID: PMC7866301 DOI: 10.4269/ajtmh.20-0537] [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: 05/24/2020] [Accepted: 10/13/2020] [Indexed: 11/07/2022] Open
Abstract
The global malaria burden has decreased substantially, but gains have been uneven both within and between countries. In Zambia, the malaria burden remains high in northern and eastern regions of the country. To effectively reduce malaria transmission in these areas, evidence-based intervention strategies are needed. Zambia’s National Malaria Control Centre conducted targeted indoor residual spraying (IRS) in 40 high-burden districts from 2014 to 2016 using the novel organophosphate insecticide pirimiphos-methyl. The Southern and Central Africa International Centers of Excellence for Malaria Research conducted an evaluation of the impact of the IRS campaign on household vector abundance in Nchelenge District, Luapula Province. From April 2012 to July 2017, field teams conducted indoor overnight vector collections from 25 to 30 households per month using Centers for Disease Control light traps. Changes in indoor anopheline counts before versus after IRS were assessed by species using negative binomial regression models with robust standard errors, controlling for geographic and climatological covariates. Counts of Anopheles funestus declined by approximately 50% in the study area and within areas targeted for IRS, and counts of Anopheles gambiae declined by approximately 40%. Within targeted areas, An. funestus counts declined more in sprayed households than in unsprayed households; however, this relationship was not observed for An. gambiae. The moderate decrease in indoor vector abundance indicates that IRS with pirimiphos-methyl is an effective vector control measure, but a more comprehensive package of interventions is needed with sufficient coverage to effectively reduce the malaria burden in this setting.
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Affiliation(s)
- Marisa A Hast
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - Jennifer C Stevenson
- Macha Research Trust, Choma, Zambia.,W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - Mbanga Muleba
- The Tropical Diseases Research Centre, Ndola, Zambia
| | - Mike Chaponda
- The Tropical Diseases Research Centre, Ndola, Zambia
| | | | - Modest Mulenga
- Department of Public Health, Michael Chilufya Sata School of Medicine, The Copperbelt University, Kitwe, Zambia
| | - Timothy Shields
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - William J Moss
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.,Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - Douglas E Norris
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
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20
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Shaw WR, Holmdahl IE, Itoe MA, Werling K, Marquette M, Paton DG, Singh N, Buckee CO, Childs LM, Catteruccia F. Multiple blood feeding in mosquitoes shortens the Plasmodium falciparum incubation period and increases malaria transmission potential. PLoS Pathog 2020; 16:e1009131. [PMID: 33382824 PMCID: PMC7774842 DOI: 10.1371/journal.ppat.1009131] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Accepted: 11/08/2020] [Indexed: 12/15/2022] Open
Abstract
Many mosquito species, including the major malaria vector Anopheles gambiae, naturally undergo multiple reproductive cycles of blood feeding, egg development and egg laying in their lifespan. Such complex mosquito behavior is regularly overlooked when mosquitoes are experimentally infected with malaria parasites, limiting our ability to accurately describe potential effects on transmission. Here, we examine how Plasmodium falciparum development and transmission potential is impacted when infected mosquitoes feed an additional time. We measured P. falciparum oocyst size and performed sporozoite time course analyses to determine the parasite's extrinsic incubation period (EIP), i.e. the time required by parasites to reach infectious sporozoite stages, in An. gambiae females blood fed either once or twice. An additional blood feed at 3 days post infection drastically accelerates oocyst growth rates, causing earlier sporozoite accumulation in the salivary glands, thereby shortening the EIP (reduction of 2.3 ± 0.4 days). Moreover, parasite growth is further accelerated in transgenic mosquitoes with reduced reproductive capacity, which mimic genetic modifications currently proposed in population suppression gene drives. We incorporate our shortened EIP values into a measure of transmission potential, the basic reproduction number R0, and find the average R0 is higher (range: 10.1%-12.1% increase) across sub-Saharan Africa than when using traditional EIP measurements. These data suggest that malaria elimination may be substantially more challenging and that younger mosquitoes or those with reduced reproductive ability may provide a larger contribution to infection than currently believed. Our findings have profound implications for current and future mosquito control interventions.
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Affiliation(s)
- W. Robert Shaw
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America
| | - Inga E. Holmdahl
- Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America
- Center for Communicable Disease Dynamics, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America
| | - Maurice A. Itoe
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America
| | - Kristine Werling
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America
| | - Meghan Marquette
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America
| | - Douglas G. Paton
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America
| | - Naresh Singh
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America
| | - Caroline O. Buckee
- Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America
- Center for Communicable Disease Dynamics, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America
| | - Lauren M. Childs
- Department of Mathematics, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Flaminia Catteruccia
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America
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21
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Epopa PS, Millogo AA, Collins CM, North AR, Benedict MQ, Tripet F, OʼLoughlin S, Dabiré RK, Ouédraogo GA, Diabaté A. Anopheles gambiae (s.l.) is found where few are looking: assessing mosquito diversity and density outside inhabited areas using diverse sampling methods. Parasit Vectors 2020; 13:516. [PMID: 33059722 PMCID: PMC7558606 DOI: 10.1186/s13071-020-04403-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Accepted: 10/09/2020] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND One of the promising current approaches to curb malaria lies in genetic vector control, the implementation of which will require an improved understanding of the movement of genetic constructs among mosquito populations. To predict potential gene flow from one area to another, it is important to begin to understand mosquito dynamics outside of the commonly-sampled village areas, and thus how genes may move between villages. This study assessed the presence and relative abundance of mosquitoes in a 6-km corridor between two villages in western Burkina Faso. METHODS The area surrounding the villages was mapped and the road between them was used as the basis of a transect along which to sample. Five collection points were placed along this transect. To investigate both larval and adult mosquito presence, multiple sampling approaches were used surrounding each point: searching for larval sites in an area of 500 m radius, swarm sampling, human landing catches (HLC), CDC light traps and backpack aspiration catches of potential resting sites. Sampling took place twice: in September and October 2015. RESULTS Adult mosquitoes from six species of Anopheles and three other genera were found along the whole transect. Anopheles gambiae (s.l.) was the most abundant followed by Anopheles nili and Anopheles coustani. Larvae of Anopheles spp. were found in small pools of surface water along the whole transect, though their presence increased with human proximity. HLC and aspiration were the most efficient methods of collecting adult mosquitoes along the whole transect, indicating that there are both host-seeking and resting mosquitoes well away from core village areas. In contrast, swarms of male mosquitoes, thought to be the principle mating locations of Anopheles spp. mosquitoes in West Africa, were only found close to the core village areas. CONCLUSIONS This preliminary study indicates that Anopheles spp. mosquitoes are both present and breeding in low human-density areas along transit axes and provides both a relative evaluation of methods for use in these areas and evidence that gene flow between Sahelian population centres is likely. More robust and structured studies are nevertheless needed to come with stronger conclusions.
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Affiliation(s)
- Patric Stephane Epopa
- Institut de Recherche en Sciences de la Santé/Centre Muraz, Bobo-Dioulasso, Burkina Faso.
| | | | | | - Ace R North
- Department of Zoology, University of Oxford, Oxford, UK
| | | | - Frederic Tripet
- Centre for Applied Entomology and Parasitology, School of Life Sciences, Keele University, Staffordshire, UK
| | | | - Roch K Dabiré
- Institut de Recherche en Sciences de la Santé/Centre Muraz, Bobo-Dioulasso, Burkina Faso
| | - Georges Anicet Ouédraogo
- Laboratoire de Recherche et d'Enseignement en Santé et Biotechnologies Animales, Université Nazi Boni (UNB), Bobo-Dioulasso, Burkina Faso
| | - Abdoulaye Diabaté
- Institut de Recherche en Sciences de la Santé/Centre Muraz, Bobo-Dioulasso, Burkina Faso
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22
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Aguilar JB, Gutierrez JB. An Epidemiological Model of Malaria Accounting for Asymptomatic Carriers. Bull Math Biol 2020; 82:42. [PMID: 32172448 PMCID: PMC7072066 DOI: 10.1007/s11538-020-00717-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 02/28/2020] [Indexed: 11/28/2022]
Abstract
Asymptomatic individuals in the context of malarial disease are subjects who carry a parasite load, but do not show clinical symptoms. A correct understanding of the influence of asymptomatic individuals on transmission dynamics will provide a comprehensive description of the complex interplay between the definitive host (female Anopheles mosquito), intermediate host (human), and agent (Plasmodium parasite). The goal of this article is to conduct a rigorous mathematical analysis of a new compartmentalized malaria model accounting for asymptomatic human hosts for the purpose of calculating the basic reproductive number ([Formula: see text]) and determining the bifurcations that might occur at the onset of disease-free equilibrium. A point of departure of this model from others appearing in the literature is that the asymptomatic compartment is decomposed into two mutually disjoint sub-compartments by making use of the naturally acquired immunity of the population under consideration. After deriving the model, a qualitative analysis is carried out to classify the stability of the equilibria of the system. Our results show that the dynamical system is locally asymptotically stable provided that [Formula: see text]. However, this stability is not global, owning to the occurrence of a sub-critical bifurcation in which additional non-trivial sub-threshold equilibrium solutions appear in response to a specified parameter being perturbed. To ensure that the model does not undergo a backward bifurcation, we demand an auxiliary parameter denoted [Formula: see text] in addition to the threshold constraint [Formula: see text]. The authors hope that this qualitative analysis will fill in the gaps of what is currently known about asymptomatic malaria and aid in designing strategies that assist the further development of malaria control and eradication efforts.
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Affiliation(s)
- Jacob B Aguilar
- Department of Mathematics and Sciences, Saint Leo University, Saint Leo, FL, 33574, USA
| | - Juan B Gutierrez
- Department of Mathematics, University of Texas at San Antonio, San Antonio, TX, 78249, USA.
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23
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Frake AN, Namaona W, Walker ED, Messina JP. Estimating spatio-temporal distributions of mosquito breeding pools in irrigated agricultural schemes: a case study at the Bwanje Valley Irrigation Scheme. Malar J 2020; 19:38. [PMID: 31969158 PMCID: PMC6977325 DOI: 10.1186/s12936-020-3113-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Accepted: 01/09/2020] [Indexed: 11/10/2022] Open
Abstract
Background The association between irrigation and the proliferation of adult mosquitoes including malaria vectors is well known; however, irrigation schemes are treated as homogenous spatio-temporal units, with little consideration for how larval breeding varies across space and time. The objective of this study was to estimate the spatio-temporal distribution of pools of water facilitating breeding at the Bwanje Valley Irrigation Scheme (BVIS) in Malawi, Africa as a function of environmental and anthropogenic characteristics. Methods Irrigation structure and land cover were quantified during the dry and rainy seasons of 2016 and 2017, respectively. These data were combined with soil type, irrigation scheduling, drainage, and maintenance to model suitability for mosquito breeding across the landscape under three scenarios: rainy season, dry season with limited water resources, and a dry season with abundant water resources. Results Results demonstrate seasonal, asymmetrical breeding potential and areas of maximum breeding potential as a function of environmental characteristics and anthropogenic influence in each scenario. The highest percentage of suitable area for breeding occurs during the rainy season; however, findings show that it is not merely the amount of water in an irrigated landscape, but the management of water resources that determines the aggregation of water bodies. In each scenario, timing and direction of irrigation along with inefficient drainage render the westernmost portion of BVIS the area of highest breeding opportunity, which expands and contracts seasonally in response to water resource availability and management decisions. Conclusions Changes in the geography of breeding potential across irrigated spaces can have profound effects on the distribution of malaria risk for those living in close proximity to irrigated agricultural schemes. The methods presented are generalizable across geographies for estimating spatio-temporal distributions of breeding risk for mosquitoes in irrigated schemes, presenting an opportunity for greater geographically targeted strategies for management.
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Affiliation(s)
- April N Frake
- Department of Geography, The University of Alabama, Tuscaloosa, AL, 35487, USA.
| | - Willy Namaona
- Agricultural Engineering Department, Lilongwe University of Agriculture and Natural Resources, Bunda College, P.O. Box 219, Lilongwe, Malawi
| | - Edward D Walker
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, 48823, USA
| | - Joseph P Messina
- College of Arts and Sciences, The University of Alabama, Tuscaloosa, AL, 35487, USA
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24
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Saddler A, Kreppel KS, Chitnis N, Smith TA, Denz A, Moore JD, Tambwe MM, Moore SJ. The development and evaluation of a self-marking unit to estimate malaria vector survival and dispersal distance. Malar J 2019; 18:441. [PMID: 31870365 PMCID: PMC6929409 DOI: 10.1186/s12936-019-3077-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Accepted: 12/14/2019] [Indexed: 01/18/2023] Open
Abstract
BACKGROUND A clear understanding of mosquito biology is fundamental to the control efforts of mosquito-borne diseases such as malaria. Mosquito mark-release-recapture (MMRR) experiments are a popular method of measuring the survival and dispersal of disease vectors; however, examples with African malaria vectors are limited. Ethical and technical difficulties involved in carrying out MMRR studies may have held back research in this area and, therefore, a device that marks mosquitoes as they emerge from breeding sites was developed and evaluated to overcome the problems of MMRR. METHODS A modified self-marking unit that marks mosquitoes with fluorescent pigment as they emerge from their breeding site was developed based on a previous design for Culex mosquitoes. The self-marking unit was first evaluated under semi-field conditions with laboratory-reared Anopheles arabiensis to determine the marking success and impact on mosquito survival. Subsequently, a field evaluation of MMRR was conducted in Yombo village, Tanzania, to examine the feasibility of the system. RESULTS During the semi-field evaluation the self-marking units successfully marked 86% of emerging mosquitoes and there was no effect of fluorescent marker on mosquito survival. The unit successfully marked wild male and female Anopheles gambiae sensu lato (s.l.) in sufficiently large numbers to justify its use in MMRR studies. The estimated daily survival probability of An. gambiae s.l. was 0.87 (95% CI 0.69-1.10) and mean dispersal distance was 579 m (95% CI 521-636 m). CONCLUSIONS This study demonstrates the successful use of a self-marking device in an MMRR study with African malaria vectors. This method may be useful in investigating population structure and dispersal of mosquitoes for deployment and evaluation of future vector control tools, such as gene drive, and to better parameterize mathematical models.
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Affiliation(s)
- Adam Saddler
- Ifakara Health Institute, Environmental Health and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania.
- Swiss Tropical & Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland.
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland.
| | - Katharina S Kreppel
- Ifakara Health Institute, Environmental Health and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
- Nelson Mandela African Institution of Science and Technology, P.O. Box 447, Tengeru, Tanzania
| | - Nakul Chitnis
- Swiss Tropical & Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland
| | - Thomas A Smith
- Swiss Tropical & Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland
| | - Adrian Denz
- Swiss Tropical & Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland
| | - Jason D Moore
- Ifakara Health Institute, Environmental Health and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
- Swiss Tropical & Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland
| | - Mgeni M Tambwe
- Ifakara Health Institute, Environmental Health and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
- Swiss Tropical & Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland
| | - Sarah J Moore
- Ifakara Health Institute, Environmental Health and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
- Swiss Tropical & Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland
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25
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Wang BG, Qiang L, Wang ZC. An almost periodic Ross-Macdonald model with structured vector population in a patchy environment. J Math Biol 2019; 80:835-863. [PMID: 31655877 DOI: 10.1007/s00285-019-01443-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Revised: 08/12/2019] [Indexed: 11/24/2022]
Abstract
An almost periodic Ross-Macdonald model with age structure for the vector population in a patchy environment is considered. The basic reproduction ratio [Formula: see text] for this model is derived and a threshold-type result on its global dynamics in terms of [Formula: see text] is established. It is shown that the disease is uniformly persistent if [Formula: see text], while the disease will die out if [Formula: see text]. Numerical simulations show that the biting rate greatly affects the disease transmission, and human migration sometimes could reduce the transmission risk. We further obtain a condition numerically to determine whether a control strategy on migration is necessary. Moreover, numerical results indicate that prolonging the length of maturation period of vector is beneficial to the disease control, and the threshold length of the maturation period for disease outbreak can be computed. Finally, the comparison between the almost periodic and periodic models shows that the periodic model may overestimate or underestimate the disease transmission risk.
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Affiliation(s)
- Bin-Guo Wang
- School of Mathematics and Statistics, Lanzhou University, Lanzhou, 730000, Gansu, People's Republic of China.
| | - Lizhong Qiang
- School of Mathematics and Statistics, Lanzhou University, Lanzhou, 730000, Gansu, People's Republic of China
| | - Zhi-Cheng Wang
- School of Mathematics and Statistics, Lanzhou University, Lanzhou, 730000, Gansu, People's Republic of China
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26
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Huestis DL, Dao A, Diallo M, Sanogo ZL, Samake D, Yaro AS, Ousman Y, Linton YM, Krishna A, Veru L, Krajacich BJ, Faiman R, Florio J, Chapman JW, Reynolds DR, Weetman D, Mitchell R, Donnelly MJ, Talamas E, Chamorro L, Strobach E, Lehmann T. Windborne long-distance migration of malaria mosquitoes in the Sahel. Nature 2019; 574:404-408. [PMID: 31578527 PMCID: PMC11095661 DOI: 10.1038/s41586-019-1622-4] [Citation(s) in RCA: 98] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Accepted: 09/06/2019] [Indexed: 11/09/2022]
Abstract
Over the past two decades efforts to control malaria have halved the number of cases globally, yet burdens remain high in much of Africa and the elimination of malaria has not been achieved even in areas where extreme reductions have been sustained, such as South Africa1,2. Studies seeking to understand the paradoxical persistence of malaria in areas in which surface water is absent for 3-8 months of the year have suggested that some species of Anopheles mosquito use long-distance migration3. Here we confirm this hypothesis through aerial sampling of mosquitoes at 40-290 m above ground level and provide-to our knowledge-the first evidence of windborne migration of African malaria vectors, and consequently of the pathogens that they transmit. Ten species, including the primary malaria vector Anopheles coluzzii, were identified among 235 anopheline mosquitoes that were captured during 617 nocturnal aerial collections in the Sahel of Mali. Notably, females accounted for more than 80% of all of the mosquitoes that we collected. Of these, 90% had taken a blood meal before their migration, which implies that pathogens are probably transported over long distances by migrating females. The likelihood of capturing Anopheles species increased with altitude (the height of the sampling panel above ground level) and during the wet seasons, but variation between years and localities was minimal. Simulated trajectories of mosquito flights indicated that there would be mean nightly displacements of up to 300 km for 9-h flight durations. Annually, the estimated numbers of mosquitoes at altitude that cross a 100-km line perpendicular to the prevailing wind direction included 81,000 Anopheles gambiae sensu stricto, 6 million A. coluzzii and 44 million Anopheles squamosus. These results provide compelling evidence that millions of malaria vectors that have previously fed on blood frequently migrate over hundreds of kilometres, and thus almost certainly spread malaria over these distances. The successful elimination of malaria may therefore depend on whether the sources of migrant vectors can be identified and controlled.
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Affiliation(s)
- Diana L Huestis
- Laboratory of Malaria and Vector Research, NIAID, NIH, Rockville, MD, USA
| | - Adama Dao
- Malaria Research and Training Center (MRTC), Faculty of Medicine, Pharmacy and Odonto-stomatology, University of Bamako, Bamako, Mali
| | - Moussa Diallo
- Malaria Research and Training Center (MRTC), Faculty of Medicine, Pharmacy and Odonto-stomatology, University of Bamako, Bamako, Mali
| | - Zana L Sanogo
- Malaria Research and Training Center (MRTC), Faculty of Medicine, Pharmacy and Odonto-stomatology, University of Bamako, Bamako, Mali
| | - Djibril Samake
- Malaria Research and Training Center (MRTC), Faculty of Medicine, Pharmacy and Odonto-stomatology, University of Bamako, Bamako, Mali
| | - Alpha S Yaro
- Malaria Research and Training Center (MRTC), Faculty of Medicine, Pharmacy and Odonto-stomatology, University of Bamako, Bamako, Mali
- Faculte des Sciences et Techniques, Universite des Sciences des Techniques et des Technologies de Bamako (FSTUSTTB), Bamako, Mali
| | - Yossi Ousman
- Malaria Research and Training Center (MRTC), Faculty of Medicine, Pharmacy and Odonto-stomatology, University of Bamako, Bamako, Mali
| | - Yvonne-Marie Linton
- Walter Reed Biosystematics Unit, Smithsonian Institution Museum Support Center, Suitland, MD, USA
- Department of Entomology, Smithsonian Institution, National Museum of Natural History, Washington, DC, USA
| | - Asha Krishna
- Laboratory of Malaria and Vector Research, NIAID, NIH, Rockville, MD, USA
| | - Laura Veru
- Laboratory of Malaria and Vector Research, NIAID, NIH, Rockville, MD, USA
| | | | - Roy Faiman
- Laboratory of Malaria and Vector Research, NIAID, NIH, Rockville, MD, USA
| | - Jenna Florio
- Laboratory of Malaria and Vector Research, NIAID, NIH, Rockville, MD, USA
| | - Jason W Chapman
- Centre for Ecology and Conservation, University of Exeter, Penryn, UK
- College of Plant Protection, Nanjing Agricultural University, Nanjing, China
- Environment and Sustainability Institute, University of Exeter, Penryn, UK
| | - Don R Reynolds
- Natural Resources Institute, University of Greenwich, Chatham, UK
- Rothamsted Research, Harpenden, UK
| | - David Weetman
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Reed Mitchell
- Walter Reed Biosystematics Unit, Smithsonian Institution Museum Support Center, Suitland, MD, USA
| | - Martin J Donnelly
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Elijah Talamas
- Systematic Entomology Laboratory - ARS, USDA, Smithsonian Institution National Museum of Natural History, Washington, DC, USA
- Florida Department of Agriculture and Consumer Services, Department of Plant Industry, Gainesville, FL, USA
| | - Lourdes Chamorro
- Department of Entomology, Smithsonian Institution, National Museum of Natural History, Washington, DC, USA
- Systematic Entomology Laboratory - ARS, USDA, Smithsonian Institution National Museum of Natural History, Washington, DC, USA
| | - Ehud Strobach
- Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, USA
- Global Modeling and Assimilation Office, NASA GSFC, Greenbelt, MD, USA
| | - Tovi Lehmann
- Laboratory of Malaria and Vector Research, NIAID, NIH, Rockville, MD, USA.
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Malinga J, Maia M, Moore S, Ross A. Can trials of spatial repellents be used to estimate mosquito movement? Parasit Vectors 2019; 12:421. [PMID: 31477155 PMCID: PMC6720076 DOI: 10.1186/s13071-019-3662-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2019] [Accepted: 08/09/2019] [Indexed: 11/16/2022] Open
Abstract
Background Knowledge of mosquito movement would aid the design of effective intervention strategies against malaria. However, data on mosquito movement through mark-recapture or genetics studies are challenging to collect, and so are not available for many sites. An additional source of information may come from secondary analyses of data from trials of repellents where household mosquito densities are collected. Using the study design of published trials, we developed a statistical model which can be used to estimate the movement between houses for mosquitoes displaced by a spatial repellent. The method uses information on the different distributions of mosquitoes between houses when no households are using spatial repellents compared to when there is incomplete coverage. The parameters to be estimated are the proportion of mosquitoes repelled, the proportion of those repelled that go to another house and the mean distance of movement between houses. Estimation is by maximum likelihood. Results We evaluated the method using simulation and found that data on the seasonal pattern of mosquito densities were required, which could be additionally collected during a trial. The method was able to provide accurate estimates from simulated data, except when the setting has few mosquitoes overall, few repelled, or the coverage with spatial repellent is low. The trial that motivated our analysis was found to have too few mosquitoes caught and repelled for our method to provide accurate results. Conclusions We propose that the method could be used as a secondary analysis of trial data to gain estimates of mosquito movement in the presence of repellents for trials with sufficient numbers of mosquitoes caught and repelled and with coverage levels which allow sufficient numbers of houses with and without repellent. Estimates from this method may supplement those from mark-release-recapture studies, and be used in designing effective malaria intervention strategies, parameterizing mathematical models and in designing trials of vector control interventions.
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Affiliation(s)
- Josephine Malinga
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Marta Maia
- KEMRI Wellcome Trust Research Programme, Kilifi, Kenya.,Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK
| | - Sarah Moore
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland.,Ifakara Health Institute, Ifakara, Tanzania
| | - Amanda Ross
- Swiss Tropical and Public Health Institute, Basel, Switzerland. .,University of Basel, Basel, Switzerland.
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Faiman R, Dao A, YARO AS, Diallo M, Djibril S, Sanogo ZL, Ousmane Y, Sullivan M, Veru L, Krajacich BJ, Krishna A, Matthews J, France CAM, Hamer G, Hobson KA, Lehmann T. Marking mosquitoes in their natural larval sites using 2H-enriched water: a promising approach for tracking over extended temporal and spatial scales. Methods Ecol Evol 2019; 10:1274-1285. [PMID: 32855783 PMCID: PMC7449266 DOI: 10.1111/2041-210x.13210] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 04/15/2019] [Indexed: 11/27/2022]
Abstract
BACKGROUND 1.Tracking mosquitoes using current methods of mark-release-recapture are limited to small spatial and temporal scales exposing major gaps in understanding long-range movements and extended survival. Novel approaches to track mosquitoes may yield fresh insights into their biology which improves intervention activities to reduce disease transmission.Stable isotope enrichment of natural mosquito breeding sites allows large-scale marking of wild mosquitoes absent human handling. Mosquito larvae that develop in 2H-enriched water are expected to be detectable for over four months using tissue mass-fraction 2H measurements, providing opportunities for long-term mark-capture studies on a large scale. APPROACH 2.A laboratory study followed by a field experiment of mosquito larval habitat 2H-enrichment was conducted in Mali, to evaluate potential labeling of wild mosquitoes. Twelve natural larval sites were enriched using [2H]-Deuterium-oxide (D2O, 99%). Enrichment level was maintained by supplementation following dilution by rains. Availability of 2H to mosquito larvae was enhanced by locally collected and cultured microorganisms (i.e. protozoa, algae and bacteria) reared in deuterated water, and provided as larval diet. Putative natural predators were removed from the larval sites and first instar larvae Anopheles gambiae s.l. larvae were added every other day. Emergence traps enabled collection of eclosing adults. Adult mosquitoes were kept at laboratory conditions for analysis of label attrition with age. RESULTS 3.Deuterium enrichment of wild mosquitoes above background levels (maximum = 143.1 ppm) became apparent 5-6 days after initial exposure, after which 2H values increased steadily until ~24 days later (to a mean of approx. 220 ppm). Anopheles and Culex mosquitoes showed significantly different 2H values (211 and 194.2 ppm respectively). Both genera exhibited exponential label attrition (e (-x)) amounting to 21.6% by day 30 post emergence, after which attrition rate continuously decreased. Males of both taxa exhibited a higher mean 2H value compared to females. CONCLUSIONS 4.Deuterium-oxide proved useful in marking mosquitoes in their natural larval sites and although costly, may prove valuable for studies of mosquitoes and other aquatic insects. Based on our field study, we provide a protocol for marking mosquito larval sites using deuterium-oxide.
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Affiliation(s)
- Roy Faiman
- Laboratory of Malaria and Vector Research, National Institute of Allergies and Infectious Diseases, the National Institutes of Health. Rockville, MD, USA
| | - Adama Dao
- Malaria Research and Training Center, Faculty of Medicine, Pharmacy and Odonto-stomatology. Bamako, Mali
| | - Alpha Seydou YARO
- Malaria Research and Training Center, Faculty of Medicine, Pharmacy and Odonto-stomatology. Bamako, Mali
| | - Moussa Diallo
- Malaria Research and Training Center, Faculty of Medicine, Pharmacy and Odonto-stomatology. Bamako, Mali
| | - Samake Djibril
- Malaria Research and Training Center, Faculty of Medicine, Pharmacy and Odonto-stomatology. Bamako, Mali
| | - Zana Lamissa Sanogo
- Malaria Research and Training Center, Faculty of Medicine, Pharmacy and Odonto-stomatology. Bamako, Mali
| | - Yossi Ousmane
- Malaria Research and Training Center, Faculty of Medicine, Pharmacy and Odonto-stomatology. Bamako, Mali
| | - Margery Sullivan
- Laboratory of Malaria and Vector Research, National Institute of Allergies and Infectious Diseases, the National Institutes of Health. Rockville, MD, USA
| | - Laura Veru
- Laboratory of Malaria and Vector Research, National Institute of Allergies and Infectious Diseases, the National Institutes of Health. Rockville, MD, USA
| | - Benjamin J. Krajacich
- Laboratory of Malaria and Vector Research, National Institute of Allergies and Infectious Diseases, the National Institutes of Health. Rockville, MD, USA
| | - Asha Krishna
- Laboratory of Malaria and Vector Research, National Institute of Allergies and Infectious Diseases, the National Institutes of Health. Rockville, MD, USA
| | - Joy Matthews
- Department of Plant Sciences, University of California Stable Isotope Facility. Davis, CA, USA
| | | | - Gabriel Hamer
- Department of Entomology, Texas A&M University. College Station, TX, USA
| | - Keith A. Hobson
- Department of Biology and Environment and Climate Change Canada, University of Western Ontario. London, Ontario, Canada
| | - Tovi Lehmann
- Laboratory of Malaria and Vector Research, National Institute of Allergies and Infectious Diseases, the National Institutes of Health. Rockville, MD, USA
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McCormack CP, Ghani AC, Ferguson NM. Fine-scale modelling finds that breeding site fragmentation can reduce mosquito population persistence. Commun Biol 2019; 2:273. [PMID: 31372512 PMCID: PMC6658551 DOI: 10.1038/s42003-019-0525-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Accepted: 06/27/2019] [Indexed: 02/03/2023] Open
Abstract
Fine-scale geographic variation in the transmission intensity of mosquito-borne diseases is primarily caused by variation in the density of female adult mosquitoes. Therefore, an understanding of fine-scale mosquito population dynamics is critical to understanding spatial heterogeneity in disease transmission and persistence at those scales. However, mathematical models of dengue and malaria transmission, which consider the dynamics of mosquito larvae, generally do not account for the fragmented structure of larval breeding sites. Here, we develop a stochastic metapopulation model of mosquito population dynamics and explore the impact of accounting for breeding site fragmentation when modelling fine-scale mosquito population dynamics. We find that, when mosquito population densities are low, fragmentation can lead to a reduction in population size, with population persistence dependent on mosquito dispersal and features of the underlying landscape. We conclude that using non-spatial models to represent fine-scale mosquito population dynamics may substantially underestimate the stochastic volatility of those populations.
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Affiliation(s)
- Clare P. McCormack
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, W2 1PG UK
| | - Azra C. Ghani
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, W2 1PG UK
| | - Neil M. Ferguson
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, W2 1PG UK
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North AR, Burt A, Godfray HCJ. Modelling the potential of genetic control of malaria mosquitoes at national scale. BMC Biol 2019; 17:26. [PMID: 30922310 PMCID: PMC6440076 DOI: 10.1186/s12915-019-0645-5] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 03/06/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The persistence of malaria in large parts of sub-Saharan Africa has motivated the development of novel tools to complement existing control programmes, including gene-drive technologies to modify mosquito vector populations. Here, we use a stochastic simulation model to explore the potential of using a driving-Y chromosome to suppress vector populations in a 106 km2 area of West Africa including all of Burkina Faso. RESULTS The consequence of driving-Y introductions is predicted to vary across the landscape, causing elimination of the target species in some regions and suppression in others. We explore how this variation is determined by environmental conditions, mosquito behaviour, and the properties of the gene-drive. Seasonality is particularly important, and we find population elimination is more likely in regions with mild dry seasons whereas suppression is more likely in regions with strong seasonality. CONCLUSIONS Despite the spatial heterogeneity, we suggest that repeated introductions of modified mosquitoes over a few years into a small fraction of human settlements may be sufficient to substantially reduce the overall number of mosquitoes across the entire geographic area.
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Affiliation(s)
- Ace R North
- Department of Zoology, University of Oxford, Oxford, UK.
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31
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Werling K, Shaw WR, Itoe MA, Westervelt KA, Marcenac P, Paton DG, Peng D, Singh N, Smidler AL, South A, Deik AA, Mancio-Silva L, Demas AR, March S, Calvo E, Bhatia SN, Clish CB, Catteruccia F. Steroid Hormone Function Controls Non-competitive Plasmodium Development in Anopheles. Cell 2019; 177:315-325.e14. [PMID: 30929905 DOI: 10.1016/j.cell.2019.02.036] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 12/14/2018] [Accepted: 02/20/2019] [Indexed: 12/26/2022]
Abstract
Transmission of malaria parasites occurs when a female Anopheles mosquito feeds on an infected host to acquire nutrients for egg development. How parasites are affected by oogenetic processes, principally orchestrated by the steroid hormone 20-hydroxyecdysone (20E), remains largely unknown. Here we show that Plasmodium falciparum development is intimately but not competitively linked to processes shaping Anopheles gambiae reproduction. We unveil a 20E-mediated positive correlation between egg and oocyst numbers; impairing oogenesis by multiple 20E manipulations decreases parasite intensities. These manipulations, however, accelerate Plasmodium growth rates, allowing sporozoites to become infectious sooner. Parasites exploit mosquito lipids for faster growth, but they do so without further affecting egg development. These results suggest that P. falciparum has adopted a non-competitive evolutionary strategy of resource exploitation to optimize transmission while minimizing fitness costs to its mosquito vector. Our findings have profound implications for currently proposed control strategies aimed at suppressing mosquito populations.
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Affiliation(s)
- Kristine Werling
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA
| | - W Robert Shaw
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA
| | - Maurice A Itoe
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA
| | - Kathleen A Westervelt
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA
| | - Perrine Marcenac
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA
| | - Douglas G Paton
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA
| | - Duo Peng
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA
| | - Naresh Singh
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA
| | - Andrea L Smidler
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA; Wyss Institute for Biologically Inspired Engineering, Boston, MA 02115, USA
| | - Adam South
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA
| | - Amy A Deik
- Broad Institute, Cambridge, MA 02142, USA
| | - Liliana Mancio-Silva
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02142, USA
| | - Allison R Demas
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02142, USA
| | - Sandra March
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02142, USA
| | - Eric Calvo
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, NIH, Rockville, MD 20852, USA
| | - Sangeeta N Bhatia
- Broad Institute, Cambridge, MA 02142, USA; Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA; Koch Institute for Integrative Cancer Research, Cambridge, MA 02142, USA; Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA
| | | | - Flaminia Catteruccia
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA.
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32
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Orsborne J, Furuya-Kanamori L, Jeffries CL, Kristan M, Mohammed AR, Afrane YA, O'Reilly K, Massad E, Drakeley C, Walker T, Yakob L. Investigating the blood-host plasticity and dispersal of Anopheles coluzzii using a novel field-based methodology. Parasit Vectors 2019; 12:143. [PMID: 30909960 PMCID: PMC6434891 DOI: 10.1186/s13071-019-3401-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Accepted: 03/15/2019] [Indexed: 11/10/2022] Open
Abstract
Background The biting behaviour and dispersal of insect vectors in the field underlies the transmission of many diseases. Here, a novel collection methodology coupled with the molecular analysis of blood-meal sources and digestion rates is introduced with the aim of aiding the understanding of two critical and relatively understudied mosquito behaviours: plasticity in blood-host choice and vector dispersal. Results A collection strategy utilising a transect of mosquito traps placed at 50 m intervals allowed the collection of blood-fed Anopheles coluzzii from a malaria-endemic village of southern Ghana where human host availability ranged from zero (a cattle pen), increasing until humans were the dominant host choice (the middle of the village). Blood-meal analysis using PCR showed statistically significant variation in blood-meal origins for mosquitoes collected across the 250 m transect: with decreasing trend in Bovine Blood Index (OR = 0.60 95% CI: 0.49–0.73, P < 0.01) and correspondingly, an increasing trend in Human Blood Index (OR = 1.50 95% CI: 1.05–2.16, P = 0.028) as the transect approached the village. Using qPCR, the host DNA remaining in the blood meal was quantified for field-caught mosquitoes and calibrated according to timed blood digestion in colony mosquitoes. Time since blood meal was consumed and the corresponding distance the vector was caught from its blood-host allowed the estimation of An. coluzzii dispersal rates. Within 7 hours of feeding, mosquitoes typically remained within 50 m of their blood-host but at 60 hours they had dispersed up to 250 m. Conclusions Using this methodology the remarkably small spatial scale at which An. coluzzii blood-host choice can change was demonstrated. In addition, conducting qPCR on host blood from field-caught mosquitoes and calibrating with timed experiments with colonised mosquitoes presents a novel methodology for investigating the dispersal behaviour of vectors. Future adaptations to this novel method to make it broadly applicable to other types of setting are also discussed.
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Affiliation(s)
- James Orsborne
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK
| | - Luis Furuya-Kanamori
- Department of Population Medicine, College of Medicine, Qatar University, Doha, Qatar.,Research School of Population Health, College of Health and Medicine, Australian National University, Canberra, Australia
| | - Claire L Jeffries
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK
| | - Mojca Kristan
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK
| | - Abdul Rahim Mohammed
- Department of Medical Microbiology, College of Health Sciences, University of Ghana, Korle Bu, Accra, Ghana
| | - Yaw A Afrane
- Department of Medical Microbiology, College of Health Sciences, University of Ghana, Korle Bu, Accra, Ghana
| | - Kathleen O'Reilly
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK
| | - Eduardo Massad
- School of Applied Mathematics, Fundacao Getulio Vargas, Rio de Janeiro, Brazil
| | - Chris Drakeley
- Department of Immunology & Infection, London School of Hygiene & Tropical Medicine, London, UK
| | - Thomas Walker
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK
| | - Laith Yakob
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK.
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Hamer GL, Bejcek JR, Valdez EA, Curtis-Robles R, Hamer SA. A Pilot Radio Telemetry Field Study of Triatomine Vectors (Hemiptera: Reduviidae) of the Chagas Disease Parasite. JOURNAL OF MEDICAL ENTOMOLOGY 2018; 55:1380-1385. [PMID: 29986045 PMCID: PMC6201830 DOI: 10.1093/jme/tjy094] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Indexed: 06/08/2023]
Abstract
We conducted the first pilot radio telemetry study of hematophagous arthropods by placing transmitters on wild-caught triatomine insects ('kissing bugs'), vectors of the Chagas disease parasite. In Texas-a recognized hotspot for triatomine diversity and locally-acquired human and animal Chagas disease-we tagged five female and four male Triatoma gerstaeckeri (Stål) (Hemiptera: Reduviidae), as well as one female and one male Triatoma sanguisuga (Leconte) (Hemiptera: Reduviidae) in three counties from 2015 to 2017. In comparative trials, placement of the transmitter on the dorsal side of the abdomen underneath the hemelytra wings, with the transmitter antenna shortened to 3 cm, yielded the best results. We tracked the movements of the 11 tagged bugs over an average of 4.8 d (range of 1 to 12 d) and detected 18 movement events with an average distance of 3.8 m (range of 1 to 20 m). This pilot study demonstrates the potential utility for using telemetry as a tool for studying fine-scale non-flight movement of triatomines and the discovery of cryptic resting habitats. Future studies using this or similar technologies to study movement and behavior of triatomines could test for site-fidelity of resting habitats and provide novel insight into aspects of vector biology that could be targeted in disease risk reduction efforts.
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Affiliation(s)
- Gabriel L Hamer
- Department of Entomology, Texas A&M University, College Station, TX
| | - Justin R Bejcek
- Department of Entomology, Texas A&M University, College Station, TX
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX
| | - Edwin A Valdez
- Department of Entomology, Texas A&M University, College Station, TX
| | - Rachel Curtis-Robles
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX
| | - Sarah A Hamer
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX
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Dambach P, Schleicher M, Korir P, Ouedraogo S, Dambach J, Sié A, Dambach M, Becker N. Nightly Biting Cycles of Anopheles Species in Rural Northwestern Burkina Faso. JOURNAL OF MEDICAL ENTOMOLOGY 2018; 55:1027-1034. [PMID: 29635478 PMCID: PMC6025195 DOI: 10.1093/jme/tjy043] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/01/2017] [Indexed: 06/08/2023]
Abstract
The biting behavior of anophelines is an important determinant of malaria transmission. Understanding the local vector host-seeking behavior, its outdoor/ indoor biting preference, and nocturnal biting periods is essential for effectively applying and improving vector control methods, such as Long Lasting Insecticidal Nets (LLINs) and personal protective measures. To better understand the biting and host-seeking patterns of Anopheles mosquitoes in Northwestern Burkina Faso, we performed biweekly Human Landing Catches (HLC) in six villages during the period of highest mosquito abundance and malaria transmission. We applied a negative binomial regression framework to statistically analyze the host-seeking activities of Anopheles species and test for differences across hours, months, and villages, as well as for differences between indoor and outdoor capture points. Anopheles gambiae s.l. was identified as the main malaria vector in this region, representing about 90% of the total anopheline population. Biting activity was significantly different across hours and showed a peaked plateau between 2000 and 0200 hours. Differences in the pattern of biting cycles were observed between the early and late rainy season. This study shows that anopheline biting activity in Northwest Burkina Faso is high throughout the night, at indoor and outdoor posts alike. Consequently, bed nets alone may not provide sufficient protection against early biting anophelines and should be complemented with additional strategies such as indoor residual spraying (IRS) and larval source management (LSM) to meet the WHO's ambitious goals that are reflected in the global technical malaria strategy for 2030.
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Affiliation(s)
- Peter Dambach
- Institute of Public Health, University of Heidelberg, Im Neuenheimer Feld Heidelberg, Germany
| | - Michael Schleicher
- Institute of Public Health, University of Heidelberg, Im Neuenheimer Feld Heidelberg, Germany
| | - Patricia Korir
- Institute of Medical Microbiology, Immunology and Parasitology, University Hospital Bonn, Bonn, Germany
| | | | | | - Ali Sié
- Zoological Research Museum Alexander Koenig, Bonn, Germany
| | - Martin Dambach
- Institute for Zoology, Department of Biology, University of Cologne, Cologne, Germany
| | - Norbert Becker
- German Mosquito Control Association (KABS), Speyer, Germany
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35
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North AR, Godfray HCJ. Modelling the persistence of mosquito vectors of malaria in Burkina Faso. Malar J 2018; 17:140. [PMID: 29609598 PMCID: PMC5879775 DOI: 10.1186/s12936-018-2288-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2017] [Accepted: 03/21/2018] [Indexed: 11/26/2022] Open
Abstract
Background Populations of the Anopheles gambiae complex are found during the rainy season throughout West Africa, even in arid areas with long dry seasons during which mosquitoes appear to be absent. Several hypotheses have been proposed to explain this apparent paradox, including aestivation, dispersal between neighbouring settlements, and long distance migration using high-altitude wind currents. Methods An individual-based, spatially explicit model of mosquito populations was developed for a region of West Africa centred on, and including all of, Burkina Faso. Populations associated with human settlements were linked by dispersal and the model incorporated geospatial data on the distribution of settlements, water bodies and rainfall. Results Local dispersal (at rates consistent with experimental data) was necessary to explain observed patterns of rainy season populations across all of the simulation area, but by itself failed to account for the presence of populations in the arid North (the Sahel). The presence of rare dry-season larval sites could explain these northern populations, but seems inconsistent with field surveys. Aestivation by female mosquitoes explained rainy-season populations in all but the very sparsest and driest areas of human habitation, while long-distance migration based on annual wind patterns could account for all observed populations. Conclusions Modelling studies such as this can help assess the potential validity of different hypotheses and suggest priority areas for experimental study. In particular, the results highlight a shortage of empirical research on mosquito dispersal between neighbouring settlements, which may be critically important to the continued presence of many mosquito populations in West Africa. Further research that establishes the extent to which mosquitoes aestivate, and migrate using high altitude winds, is also much needed to understand Sahelian mosquito populations. Electronic supplementary material The online version of this article (10.1186/s12936-018-2288-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Ace R North
- Department of Zoology, University of Oxford, Woodstock Road, Oxford, OX2 6GG, UK.
| | - H Charles J Godfray
- Department of Zoology, University of Oxford, Woodstock Road, Oxford, OX2 6GG, UK
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36
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Huestis DL, Artis ML, Armbruster PA, Lehmann T. Photoperiodic responses of Sahelian malaria mosquitoes Anopheles coluzzii and An. arabiensis. Parasit Vectors 2017; 10:621. [PMID: 29282150 PMCID: PMC5745990 DOI: 10.1186/s13071-017-2556-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 11/26/2017] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Throughout large parts of sub-Saharan Africa, seasonal malaria transmission follows mosquito density, approaching zero during the dry season and peaking during the wet season. The mechanisms by which malaria mosquitoes survive the long dry season, when no larval sites are available remain largely unknown, despite being long recognized as a critical target for vector control. Previous work in the West African Sahel has led to the hypothesis that Anopheles coluzzii (formerly M-form Anopheles gambiae) undergoes aestivation (dry-season diapause), while Anopheles gambiae (s.s.) (formerly S-form An. gambiae) and Anopheles arabiensis repopulate each wet season via long-distance migration. The environmental cues used by these species to signal the oncoming dry season have not been determined; however, studies, mostly addressing mosquitoes from temperate zones, have highlighted photoperiod and temperature as the most common token stimuli for diapause initiation. We subjected newly established colonies of An. coluzzii and An. arabiensis from the Sahel to changes in photoperiod to assess and compare their responses in terms of longevity and other relevant phenotypes. RESULTS Our results showed that short photoperiod alone and to a lesser extent, lower nightly temperature (representing the early dry season), significantly increased longevity of An. coluzzii (by ~30%, P < 0.001) but not of An. arabiensis. Further, dry season conditions increased body size but not relative lipid content of An. coluzzii, whereas body size of An. arabiensis decreased under these conditions. CONCLUSIONS These species-specific responses underscore the capacity of tropical anophelines to detect mild changes (~1 h) in photoperiod and thus support the role of photoperiod as a token stimulus for An. coluzzii in induction of aestivation, although, these responses fall short of a complete recapitulation of aestivation under laboratory conditions.
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Affiliation(s)
- Diana L. Huestis
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD USA
| | - Monica L. Artis
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD USA
| | | | - Tovi Lehmann
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD USA
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Temporal variation in confirmed diagnosis of fever-related malarial cases among children under-5 years by community health workers and in health facilities between years 2013 and 2015 in Siaya County, Kenya. Malar J 2017; 16:454. [PMID: 29121954 PMCID: PMC5679183 DOI: 10.1186/s12936-017-2100-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 10/31/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Malaria case management continues to experience dynamic changes. Building community capacity is instrumental in both prevention and treatment of malaria. The World Health Organization (WHO) recommends utilization of well-trained and supervised community health workers (CHWs) to reduce the burden of malaria deaths among children under-5 years of age in Africa. Longitudinally-tracked information on utilization of CHWs by communities in terms of trends in diagnosis of malaria in children under-5 years of age is essential in influencing national and local malaria control policies and strategies. METHODS A desktop review was carried out of a database consisting of confirmed uncomplicated malaria cases in 10 villages using CHWs and out-patient departments of 10 health facilities in children under-five for the period of 3 years between January 2013 and December 2015. Analyses of association between the diagnosed cases and satellite-based rainfall, village and time (months and years) were carried out using a Poisson regression model. RESULTS Analysis of malaria diagnoses made by CHWs showed the following trends: (i) the incidence of reported documented malaria-positive fever cases increased with time (2013-2015) and the difference over the years was statistically significant (P < 0.001), (ii) specific village was significantly associated (P < 0.001) with reporting malaria-positive fever cases, (iii) the long-term monthly sequence starting from highest to lowest incidence of reported malaria-positive fever cases was July, May and June, March, August, April, September, November, and February, October and, finally, January, and the difference in reported malaria-positives between the months was statistically significant (P = 0.001) and (iv) none of the tested rainfall regimes (current, lagged or cumulative) was associated with reported malaria-positive fever cases during the 3-year period (P > 0.1). Looking at the number of diagnoses made at the health facilities, (i) The number of reported malaria-positive fever cases decreased with time (2013-2015) and the difference among the years was not statistically significant (P = 0.399), (ii) The long-term monthly sequence starting from highest to lowest number of reported malaria-positive fever cases was July, June, May, April, January, August, March, February, September, November, October and December, and the difference between the months was statistically significant (P < 0.001). CONCLUSIONS CHWs have the potential to play a major role in diagnosing and treating malaria, thereby decreasing under-five children mortality. Temporally, the risk of diagnosing malaria seems predictable and this may present opportunities for policy-targeted malaria preparedness and control. The findings are expected to support policy actions that may scale-up community health services in remote rural settings.
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Epopa PS, Millogo AA, Collins CM, North A, Tripet F, Benedict MQ, Diabate A. The use of sequential mark-release-recapture experiments to estimate population size, survival and dispersal of male mosquitoes of the Anopheles gambiae complex in Bana, a west African humid savannah village. Parasit Vectors 2017; 10:376. [PMID: 28784147 PMCID: PMC5547516 DOI: 10.1186/s13071-017-2310-6] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Accepted: 07/26/2017] [Indexed: 12/14/2022] Open
Abstract
Background Vector control is a major component of the malaria control strategy. The increasing spread of insecticide resistance has encouraged the development of new tools such as genetic control which use releases of modified male mosquitoes. The use of male mosquitoes as part of a control strategy requires an improved understanding of male mosquito biology, including the factors influencing their survival and dispersal, as well as the ability to accurately estimate the size of a target mosquito population. This study was designed to determine the seasonal variation in population size via repeated mark-release-recapture experiments and to estimate the survival and dispersal of male mosquitoes of the Anopheles gambiae complex in a small west African village. Methods Mark-release-recapture experiments were carried out in Bana Village over two consecutive years, during the wet and the dry seasons. For each experiment, around 5000 (3407–5273) adult male Anopheles coluzzii mosquitoes were marked using three different colour dye powders (red, blue and green) and released in three different locations in the village (centre, edge and outside). Mosquitoes were recaptured at sites spread over the village for seven consecutive days following the releases. Three different capture methods were used: clay pots, pyrethroid spray catches and swarm sampling. Results Swarm sampling was the most productive method for recapturing male mosquitoes in the field. Population size and survival were estimated by Bayesian analyses of the Fisher-Ford model, revealing an about 10-fold increase in population size estimates between the end of dry season (10,000–50,000) to the wet season (100,000–500,000). There were no detectable seasonal effects on mosquito survival, suggesting that factors other than weather may play an important role. Mosquito dispersal ranged from 40 to 549 m over the seven days of each study and was not influenced by the season, but mainly by the release location, which explained more than 44% of the variance in net dispersal distance. Conclusion This study clearly shows that male-based MRR experiments can be used to estimate some parameters of wild male populations such as population size, survival, and dispersal and to estimate the spatial patterns of movement in a given locality.
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Affiliation(s)
- Patric Stephane Epopa
- Institut de Recherche en Sciences de la Santé / Centre Muraz, Bobo-Dioulasso, Burkina Faso.
| | | | | | - Ace North
- Department of Zoology, University of Oxford, Oxford, UK
| | - Frederic Tripet
- Centre for Applied Entomology and Parasitology, School of Life Sciences, Keele University, Keele, Staffordshire, UK
| | | | - Abdoulaye Diabate
- Institut de Recherche en Sciences de la Santé / Centre Muraz, Bobo-Dioulasso, Burkina Faso
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Villela DAM, Garcia GDA, Maciel-de-Freitas R. Novel inference models for estimation of abundance, survivorship and recruitment in mosquito populations using mark-release-recapture data. PLoS Negl Trop Dis 2017. [PMID: 28650962 PMCID: PMC5501687 DOI: 10.1371/journal.pntd.0005682] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Background Experiments involving mosquito mark-release-recapture (MRR) design are helpful to determine abundance, survival and even recruitment of mosquito populations in the field. Obstacles in mosquito MRR protocols include marking limitations due to small individual size, short lifespan, low efficiency in capturing devices such as traps, and individual removal upon capture. These limitations usually make MRR analysis restricted to only abundance estimation or a combination of abundance and survivorship, and often generate a great degree of uncertainty about the estimations. Methodology/Principal findings We present a set of Bayesian biodemographic models designed to fit data from most common mosquito recapture experiments. Using both field data and simulations, we consider model features such as capture efficiency, survival rates, removal of individuals due to capturing, and collection of pupae. These models permit estimation of abundance, survivorship of both marked and unmarked mosquitoes, if different, and recruitment rate. We analyze the accuracy of estimates by varying the number of released individuals, abundance, survivorship, and capture efficiency in multiple simulations. These methods can stand capture efficiencies as low as usually reported but their accuracy depends on the number of released mosquitoes, abundance and survivorship. We also show that gathering pupal counts allows estimating differences in survivorship between released mosquitoes and the unmarked population. Conclusion/Significance These models are important both to reduce uncertainty in evaluating MMR experiments and also to help planning future MRR studies. Mosquito-borne diseases such as dengue and malaria impose a global burden with recurrent outbreaks. Recently, emergence of arboviral diseases caused by Zika and chikungunya viruses has also become a global concern. Knowledge about the ecology of mosquito populations under natural conditions may provide significant aid to help designing more effective vector control strategies. Quantitative metrics such as the abundance of mosquito populations are difficult to be measured in the field without resorting to experiments with markers. There are, however, limitations to these kinds of experiments such as short mosquito lifespan, marking limitations due to small body size, low efficiency in capturing devices such as traps, and once-only individual capture. Due to these limitations most methods estimate either only abundance or a combination of abundance and survivorship. In this work, we present statistical methods designed to estimate abundance, survivorship and recruitment using inference models and information such as counts of pupae. Results indicate that having low capture efficiencies as often observed in field assays still permits good estimation. Also, low number of released mosquitoes compromise density and survival estimations. We expect these methods to be helpful to people collecting mosquito field data and for health analysts to evaluate possible outcomes of control interventions.
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Affiliation(s)
| | - Gabriela de Azambuja Garcia
- Laboratório de Transmissão de Hematozoários, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro, Brazil
| | - Rafael Maciel-de-Freitas
- Laboratório de Transmissão de Hematozoários, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro, Brazil
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Ayala D, Acevedo P, Pombi M, Dia I, Boccolini D, Costantini C, Simard F, Fontenille D. Chromosome inversions and ecological plasticity in the main African malaria mosquitoes. Evolution 2017; 71:686-701. [PMID: 28071788 DOI: 10.1111/evo.13176] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 12/22/2016] [Indexed: 01/30/2023]
Abstract
Chromosome inversions have fascinated the scientific community, mainly because of their role in the rapid adaption of different taxa to changing environments. However, the ecological traits linked to chromosome inversions have been poorly studied. Here, we investigated the roles played by 23 chromosome inversions in the adaptation of the four major African malaria mosquitoes to local environments in Africa. We studied their distribution patterns by using spatially explicit modeling and characterized the ecogeographical determinants of each inversion range. We then performed hierarchical clustering and constrained ordination analyses to assess the spatial and ecological similarities among inversions. Our results show that most inversions are environmentally structured, suggesting that they are actively involved in processes of local adaptation. Some inversions exhibited similar geographical patterns and ecological requirements among the four mosquito species, providing evidence for parallel evolution. Conversely, common inversion polymorphisms between sibling species displayed divergent ecological patterns, suggesting that they might have a different adaptive role in each species. These results are in agreement with the finding that chromosomal inversions play a role in Anopheles ecotypic adaptation. This study establishes a strong ecological basis for future genome-based analyses to elucidate the genetic mechanisms of local adaptation in these four mosquitoes.
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Affiliation(s)
- Diego Ayala
- UMR 224 MIVEGEC/ESV, IRD, Montpellier, 34394, France.,CIRMF, BP 769, Franceville, Gabon
| | - Pelayo Acevedo
- SaBio, Instituto de Investigación en Recursos Cinegéticos (IREC), CSIC-UCLM-JCCM, Ciudad Real, 13005, Spain
| | - Marco Pombi
- Sezione di Parassitologia, Dipartimento di Scienze di Sanità Pubblica, Università di Roma "La Sapienza,", Rome, 00185, Italy
| | - Ibrahima Dia
- Medical Entomology Unit, Institut Pasteur de Dakar, BP 220, Dakar, Senegal
| | - Daniela Boccolini
- Department MIPI, Unit Vector-Borne Diseases and International Health, Istituto Superiore di Sanità, Rome, 00161, Italy
| | | | | | - Didier Fontenille
- UMR 224 MIVEGEC/ESV, IRD, Montpellier, 34394, France.,Current Address: Institut Pasteur du Cambodge, BP 983, Phnom Penh, Cambodia
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Mulenge FM, Hunja CW, Magiri E, Culleton R, Kaneko A, Aman RA. Genetic Diversity and Population Structure of Plasmodium falciparum in Lake Victoria Islands, A Region of Intense Transmission. Am J Trop Med Hyg 2016; 95:1077-1085. [PMID: 27601522 PMCID: PMC5094220 DOI: 10.4269/ajtmh.16-0383] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 07/17/2016] [Indexed: 11/07/2022] Open
Abstract
Understanding the genetic structure and transmission dynamics of Plasmodium falciparum parasites in malaria-endemic regions is crucial before the implementation of interventions. Located in a high-transmission region of western Kenya where P. falciparum is the predominant species, the Lake Victoria islands are ideal for feasibility of malaria elimination studies. We analyzed genetic variation in eight microsatellite loci to examine parasite population structure and gene flow patterns across five sites. High levels of genetic diversity were measured throughout the region (mean heterozygosity index = 0.84). The overall fixation index value between the sites was 0.044, indicating that approximately 5% of the overall allelic variation is due to differences between the populations. Based on these results, we concluded that parasite population structure in the studied islands is shaped by human migration patterns that maintain extensive parasite gene flow between the sites. Consequently, any malaria elimination and interventions strategies in the study area will have to be carried out broadly on all four islands and adjoining mainland region.
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Affiliation(s)
- Felix M Mulenge
- Department of Biochemistry, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya.
| | | | - Esther Magiri
- Department of Biochemistry, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya
| | - Richard Culleton
- Malaria Unit, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
| | - Akira Kaneko
- Island Malaria Group, Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
- Department of Parasitology, Graduate School of Medicine, Osaka City University, Osaka, Japan
| | - Rashid A Aman
- Center for Research in Therapeutic Sciences, Strathmore University, Nairobi, Kenya
- African Center for Clinical Trials, Nairobi, Kenya
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Shaw WR, Marcenac P, Childs LM, Buckee CO, Baldini F, Sawadogo SP, Dabiré RK, Diabaté A, Catteruccia F. Wolbachia infections in natural Anopheles populations affect egg laying and negatively correlate with Plasmodium development. Nat Commun 2016; 7:11772. [PMID: 27243367 PMCID: PMC4895022 DOI: 10.1038/ncomms11772] [Citation(s) in RCA: 91] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Accepted: 04/27/2016] [Indexed: 11/21/2022] Open
Abstract
The maternally inherited alpha-proteobacterium Wolbachia has been proposed as a tool to block transmission of devastating mosquito-borne infectious diseases like dengue and malaria. Here we study the reproductive manipulations induced by a recently identified Wolbachia strain that stably infects natural mosquito populations of a major malaria vector, Anopheles coluzzii, in Burkina Faso. We determine that these infections significantly accelerate egg laying but do not induce cytoplasmic incompatibility or sex-ratio distortion, two parasitic reproductive phenotypes that facilitate the spread of other Wolbachia strains within insect hosts. Analysis of 221 blood-fed A. coluzzii females collected from houses shows a negative correlation between the presence of Plasmodium parasites and Wolbachia infection. A mathematical model incorporating these results predicts that infection with these endosymbionts may reduce malaria prevalence in human populations. These data suggest that Wolbachia may be an important player in malaria transmission dynamics in Sub-Saharan Africa. Wolbachia bacteria infect insects and could potentially be used to control populations of malaria-transmitting mosquitoes. Here, the authors provide evidence that natural Wolbachia infections affect the rate of egg laying and are associated with reduced presence of malaria parasites in Anopheles mosquitoes.
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Affiliation(s)
- W Robert Shaw
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts 02115, USA
| | - Perrine Marcenac
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts 02115, USA
| | - Lauren M Childs
- Center for Communicable Disease Dynamics, Harvard T.H. Chan School of Public Health, Boston, Massachusetts 02115, USA.,Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, Massachusetts 02115, USA
| | - Caroline O Buckee
- Center for Communicable Disease Dynamics, Harvard T.H. Chan School of Public Health, Boston, Massachusetts 02115, USA.,Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, Massachusetts 02115, USA
| | - Francesco Baldini
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow G12 8QQ, UK
| | - Simon P Sawadogo
- Institut de Recherche en Sciences de la Santé/Centre Muraz, O1 BP 390 Bobo-Dioulasso 01, Burkina Faso
| | - Roch K Dabiré
- Institut de Recherche en Sciences de la Santé/Centre Muraz, O1 BP 390 Bobo-Dioulasso 01, Burkina Faso
| | - Abdoulaye Diabaté
- Institut de Recherche en Sciences de la Santé/Centre Muraz, O1 BP 390 Bobo-Dioulasso 01, Burkina Faso
| | - Flaminia Catteruccia
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts 02115, USA
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43
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Buck M, Nilsson LKJ, Brunius C, Dabiré RK, Hopkins R, Terenius O. Bacterial associations reveal spatial population dynamics in Anopheles gambiae mosquitoes. Sci Rep 2016; 6:22806. [PMID: 26960555 PMCID: PMC4785398 DOI: 10.1038/srep22806] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Accepted: 02/19/2016] [Indexed: 02/04/2023] Open
Abstract
The intolerable burden of malaria has for too long plagued humanity and the prospect of eradicating malaria is an optimistic, but reachable, target in the 21(st) century. However, extensive knowledge is needed about the spatial structure of mosquito populations in order to develop effective interventions against malaria transmission. We hypothesized that the microbiota associated with a mosquito reflects acquisition of bacteria in different environments. By analyzing the whole-body bacterial flora of An. gambiae mosquitoes from Burkina Faso by 16 S amplicon sequencing, we found that the different environments gave each mosquito a specific bacterial profile. In addition, the bacterial profiles provided precise and predicting information on the spatial dynamics of the mosquito population as a whole and showed that the mosquitoes formed clear local populations within a meta-population network. We believe that using microbiotas as proxies for population structures will greatly aid improving the performance of vector interventions around the world.
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Affiliation(s)
- Moritz Buck
- Evolutionary Biology Center and Bioinformatics Infrastructure for Life Sciences, Uppsala University, Norbyvägen 18D, 752 36 Uppsala Sweden
| | - Louise K J Nilsson
- Department of Ecology, Swedish University of Agricultural Sciences (SLU), 750 07 Uppsala, Sweden
| | - Carl Brunius
- Department of Food Science, Swedish University of Agricultural Sciences (SLU), 750 07 Uppsala, Sweden
| | - Roch K Dabiré
- Institut de Recherche en Sciences de la Santé/Centre Muraz, O1 BP 390 Bobo-Dioulasso 01, Burkina Faso
| | - Richard Hopkins
- Department of Ecology, Swedish University of Agricultural Sciences (SLU), 750 07 Uppsala, Sweden.,Natural Resources Institute, University of Greenwich, Central Avenue, Chatham Maritime, Kent, ME4 4TB, United Kingdom
| | - Olle Terenius
- Department of Ecology, Swedish University of Agricultural Sciences (SLU), 750 07 Uppsala, Sweden
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44
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Ryan SJ, Ben-Horin T, Johnson LR. Malaria control and senescence: the importance of accounting for the pace and shape of aging in wild mosquitoes. Ecosphere 2015. [DOI: 10.1890/es15-00094.1] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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45
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Villela DAM, Codeço CT, Figueiredo F, Garcia GA, Maciel-de-Freitas R, Struchiner CJ. A Bayesian Hierarchical Model for Estimation of Abundance and Spatial Density of Aedes aegypti. PLoS One 2015; 10:e0123794. [PMID: 25906323 PMCID: PMC4408040 DOI: 10.1371/journal.pone.0123794] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2014] [Accepted: 03/06/2015] [Indexed: 11/22/2022] Open
Abstract
Strategies to minimize dengue transmission commonly rely on vector control, which aims to maintain Ae. aegypti density below a theoretical threshold. Mosquito abundance is traditionally estimated from mark-release-recapture (MRR) experiments, which lack proper analysis regarding accurate vector spatial distribution and population density. Recently proposed strategies to control vector-borne diseases involve replacing the susceptible wild population by genetically modified individuals' refractory to the infection by the pathogen. Accurate measurements of mosquito abundance in time and space are required to optimize the success of such interventions. In this paper, we present a hierarchical probabilistic model for the estimation of population abundance and spatial distribution from typical mosquito MRR experiments, with direct application to the planning of these new control strategies. We perform a Bayesian analysis using the model and data from two MRR experiments performed in a neighborhood of Rio de Janeiro, Brazil, during both low- and high-dengue transmission seasons. The hierarchical model indicates that mosquito spatial distribution is clustered during the winter (0.99 mosquitoes/premise 95% CI: 0.80-1.23) and more homogeneous during the high abundance period (5.2 mosquitoes/premise 95% CI: 4.3-5.9). The hierarchical model also performed better than the commonly used Fisher-Ford's method, when using simulated data. The proposed model provides a formal treatment of the sources of uncertainty associated with the estimation of mosquito abundance imposed by the sampling design. Our approach is useful in strategies such as population suppression or the displacement of wild vector populations by refractory Wolbachia-infected mosquitoes, since the invasion dynamics have been shown to follow threshold conditions dictated by mosquito abundance. The presence of spatially distributed abundance hotspots is also formally addressed under this modeling framework and its knowledge deemed crucial to predict the fate of transmission control strategies based on the replacement of vector populations.
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Affiliation(s)
| | - Claudia T. Codeço
- Fundação Oswaldo Cruz, Programa de Computação Científica—Rio de Janeiro, Brazil
| | - Felipe Figueiredo
- Fundação Oswaldo Cruz, Programa de Computação Científica—Rio de Janeiro, Brazil
| | - Gabriela A. Garcia
- Fundação Oswaldo Cruz, Departamento de Entomologia, Laboratório de Transmissores de Hematozoários—Rio de Janeiro, Brazil
| | - Rafael Maciel-de-Freitas
- Fundação Oswaldo Cruz, Departamento de Entomologia, Laboratório de Transmissores de Hematozoários—Rio de Janeiro, Brazil
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Tene Fossog B, Ayala D, Acevedo P, Kengne P, Ngomo Abeso Mebuy I, Makanga B, Magnus J, Awono-Ambene P, Njiokou F, Pombi M, Antonio-Nkondjio C, Paupy C, Besansky NJ, Costantini C. Habitat segregation and ecological character displacement in cryptic African malaria mosquitoes. Evol Appl 2015; 8:326-45. [PMID: 25926878 PMCID: PMC4408144 DOI: 10.1111/eva.12242] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Accepted: 12/08/2014] [Indexed: 01/09/2023] Open
Abstract
Understanding how divergent selection generates adaptive phenotypic and population diversification provides a mechanistic explanation of speciation in recently separated species pairs. Towards this goal, we sought ecological gradients of divergence between the cryptic malaria vectors Anopheles coluzzii and An. gambiae and then looked for a physiological trait that may underlie such divergence. Using a large set of occurrence records and eco-geographic information, we built a distribution model to predict the predominance of the two species across their range of sympatry. Our model predicts two novel gradients along which the species segregate: distance from the coastline and altitude. Anopheles coluzzii showed a ‘bimodal’ distribution, predominating in xeric West African savannas and along the western coastal fringe of Africa. To test whether differences in salinity tolerance underlie this habitat segregation, we assessed the acute dose–mortality response to salinity of thirty-two larval populations from Central Africa. In agreement with its coastal predominance, Anopheles coluzzii was overall more tolerant than An. gambiae. Salinity tolerance of both species, however, converged in urban localities, presumably reflecting an adaptive response to osmotic stress from anthropogenic pollutants. When comparing degree of tolerance in conjunction with levels of syntopy, we found evidence of character displacement in this trait.
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Affiliation(s)
- Billy Tene Fossog
- Institut de Recherche pour le Développement (IRD), UMR MIVEGEC (UM1, UM2, CNRS 5290, IRD 224) Montpellier, France ; Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC) Yaoundé, Cameroon ; Department of Animal Biology, Faculty of Sciences, University of Yaoundé I Yaoundé, Cameroon
| | - Diego Ayala
- Institut de Recherche pour le Développement (IRD), UMR MIVEGEC (UM1, UM2, CNRS 5290, IRD 224) Montpellier, France ; Eck Institute for Global Health & Department of Biological Sciences, University of Notre Dame Notre Dame, IN, USA ; Centre International de Recherches Médicales de Franceville (CIRMF) Franceville, Gabon
| | - Pelayo Acevedo
- SaBio, Instituto de Investigación en Recursos Cinegéticos (IREC), CSIC-UCLM-JCCM Ciudad Real, Spain
| | - Pierre Kengne
- Institut de Recherche pour le Développement (IRD), UMR MIVEGEC (UM1, UM2, CNRS 5290, IRD 224) Montpellier, France ; Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC) Yaoundé, Cameroon
| | | | - Boris Makanga
- Institut de Recherche pour le Développement (IRD), UMR MIVEGEC (UM1, UM2, CNRS 5290, IRD 224) Montpellier, France ; Centre International de Recherches Médicales de Franceville (CIRMF) Franceville, Gabon ; Institut de Recherche en Ecologie Tropicale (IRET) Libreville, Gabon
| | - Julie Magnus
- Centre International de Recherches Médicales de Franceville (CIRMF) Franceville, Gabon
| | - Parfait Awono-Ambene
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC) Yaoundé, Cameroon
| | - Flobert Njiokou
- Department of Animal Biology, Faculty of Sciences, University of Yaoundé I Yaoundé, Cameroon
| | - Marco Pombi
- Sezione di Parassitologia, Dipartimento di Sanità Pubblica e Malattie Infettive, Università di Roma 'La Sapienza' Rome, Italy
| | - Christophe Antonio-Nkondjio
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC) Yaoundé, Cameroon
| | - Christophe Paupy
- Institut de Recherche pour le Développement (IRD), UMR MIVEGEC (UM1, UM2, CNRS 5290, IRD 224) Montpellier, France ; Centre International de Recherches Médicales de Franceville (CIRMF) Franceville, Gabon
| | - Nora J Besansky
- Eck Institute for Global Health & Department of Biological Sciences, University of Notre Dame Notre Dame, IN, USA
| | - Carlo Costantini
- Institut de Recherche pour le Développement (IRD), UMR MIVEGEC (UM1, UM2, CNRS 5290, IRD 224) Montpellier, France ; Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC) Yaoundé, Cameroon
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Gouagna LC, Dehecq JS, Fontenille D, Dumont Y, Boyer S. Seasonal variation in size estimates of Aedes albopictus population based on standard mark-release-recapture experiments in an urban area on Reunion Island. Acta Trop 2015; 143:89-96. [PMID: 25592432 DOI: 10.1016/j.actatropica.2014.12.011] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Revised: 12/22/2014] [Accepted: 12/26/2014] [Indexed: 11/27/2022]
Abstract
The implementation of the sterile insect technique for area-wide vector control requires that natural population density be accurately estimated to determine both the appropriate time to treat and the adequate number of sterile males for release. Herein, we used mark-release-recapture (MRR) to derive seasonal abundance estimates of Aedes albopictus population sizes within a delimited geographical area in Reunion Island. Population size of Ae. albopictus was estimated through four mark-release-recapture experiments carried out separately in different seasons. Marked males and females were released each time, and recaptured using BG sentinel traps for six consecutive days. Data were used to estimate the population size using a conceptual model that incorporates the variation in daily mortality rates. The likely influence of environmental factors on the magnitude of catches and on population fluctuation was analyzed. A total of 2827 mosquitoes (1914 males and 913 females) were marked and released on four occasions during dry and wet seasons. After release, 138 males (7.21%) and 86 females (9.41%) of the marked specimens were recaptured in subsequent samplings. The effectiveness of the daily captures of wild and released mosquitoes was significantly influenced by meteorological conditions such as temperature, rainfall, wind speed and light intensity. The estimates of Ae. albopictus population size obtained with our model estimator ranged from 298 to 1238 males and 604 to 2208 females per ha, with seasonal variability - higher population size in the humid season. The presented results will be essential in designing more effective sterile male release strategies for long-term suppression of wild Ae. albopictus populations.
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Hardy A, Mageni Z, Dongus S, Killeen G, Macklin MG, Majambare S, Ali A, Msellem M, Al-Mafazy AW, Smith M, Thomas C. Mapping hotspots of malaria transmission from pre-existing hydrology, geology and geomorphology data in the pre-elimination context of Zanzibar, United Republic of Tanzania. Parasit Vectors 2015; 8:41. [PMID: 25608875 PMCID: PMC4307680 DOI: 10.1186/s13071-015-0652-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Accepted: 01/11/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Larval source management strategies can play an important role in malaria elimination programmes, especially for tackling outdoor biting species and for eliminating parasite and vector populations when they are most vulnerable during the dry season. Effective larval source management requires tools for identifying geographic foci of vector proliferation and malaria transmission where these efforts may be concentrated. Previous studies have relied on surface topographic wetness to indicate hydrological potential for vector breeding sites, but this is unsuitable for karst (limestone) landscapes such as Zanzibar where water flow, especially in the dry season, is subterranean and not controlled by surface topography. METHODS We examine the relationship between dry and wet season spatial patterns of diagnostic positivity rates of malaria infection amongst patients reporting to health facilities on Unguja, Zanzibar, with the physical geography of the island, including land cover, elevation, slope angle, hydrology, geology and geomorphology in order to identify transmission hot spots using Boosted Regression Trees (BRT) analysis. RESULTS The distribution of both wet and dry season malaria infection rates can be predicted using freely available static data, such as elevation and geology. Specifically, high infection rates in the central and southeast regions of the island coincide with outcrops of hard dense limestone which cause locally elevated water tables and the location of dolines (shallow depressions plugged with fine-grained material promoting the persistence of shallow water bodies). CONCLUSIONS This analysis provides a tractable tool for the identification of malaria hotspots which incorporates subterranean hydrology, which can be used to target larval source management strategies.
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Affiliation(s)
- Andrew Hardy
- Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, UK.
| | - Zawadi Mageni
- Environmental Health and Ecological Sciences, Ifakara Health Institute, Ifakara, United Republic of Tanzania.
| | - Stefan Dongus
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland.
| | - Gerry Killeen
- Environmental Health and Ecological Sciences, Ifakara Health Institute, Ifakara, United Republic of Tanzania.
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, UK.
| | - Mark G Macklin
- Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, UK.
| | - Silas Majambare
- Environmental Health and Ecological Sciences, Ifakara Health Institute, Ifakara, United Republic of Tanzania.
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, UK.
| | - Abdullah Ali
- Zanzibar Malaria Elimination Program, Zanzibar, United Republic of Tanzania.
| | - Mwinyi Msellem
- Zanzibar Malaria Elimination Program, Zanzibar, United Republic of Tanzania.
| | | | - Mark Smith
- School of Geography, University of Leeds, Leeds, UK.
| | - Chris Thomas
- Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Aberystwyth, UK.
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Ageep TB, Damiens D, Alsharif B, Ahmed A, Salih EHO, Ahmed FTA, Diabaté A, Lees RS, Gilles JRL, El Sayed BB. Participation of irradiated Anopheles arabiensis males in swarms following field release in Sudan. Malar J 2014; 13:484. [PMID: 25495146 PMCID: PMC4295471 DOI: 10.1186/1475-2875-13-484] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Accepted: 11/20/2014] [Indexed: 11/30/2022] Open
Abstract
Background The success of the sterile insect technique (SIT) depends the release of large numbers of sterile males, which are able to compete for mates with the wild male population within the target area. Unfortunately, the processes of colonisation, mass production and irradiation may reduce the competitiveness of sterile males through genetic selection, loss of natural traits and somatic damage. In this context, the capacity of released sterile Anopheles arabiensis males to survive, disperse and participate in swarms at occurring at varying distances from the release site was studied using mark-release-recapture (MRR) techniques. Methods In order to assess their participation in swarms, irradiated and marked laboratory-reared male mosquitoes were released 50, 100 or 200 m from the known site of a large swarm on three consecutive nights. Males were collected from this large swarm on subsequent nights. Over the three days a total of 8,100 males were released. Mean distance travelled (MDT), daily probability of survival and estimated population size were calculated from the recapture data. An effect of male age at the time of release on these parameters was observed. Results Five per cent of the males released over three days were recaptured. In two-, three- and four-day-old males, MDT was 118, 178 and 170 m, and the daily survival probability 0.95, 0.90 and 0.75, respectively. From the recapture data on the first day following each release, the Lincoln index gives an estimation of 32,546 males in the natural population. Discussion Sterile An. arabiensis males released into the field were able to find and participate in existing swarms, and possibly even initiate swarms. The survival probability decreased with the age of male on release but the swarm participation and the distance travelled by older males seemed higher than for younger males. The inclusion of a pre-release period may thus be beneficial to male competitiveness and increase the attractiveness of adult sexing techniques, such as blood spiking.
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Affiliation(s)
| | - David Damiens
- Insect Pest Control Laboratory, Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture, International Atomic Energy Agency, Wagramerstraße 5, PO Box 100A-1400 Vienna, Austria.
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Gao D, Lou Y, Ruan S. A PERIODIC ROSS-MACDONALD MODEL IN A PATCHY ENVIRONMENT. DISCRETE AND CONTINUOUS DYNAMICAL SYSTEMS. SERIES B 2014; 19:3133-3145. [PMID: 25473381 PMCID: PMC4244283 DOI: 10.3934/dcdsb.2014.19.3133] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Based on the classical Ross-Macdonald model, in this paper we propose a periodic malaria model to incorporate the effects of temporal and spatial heterogeneity on disease transmission. The temporal heterogeneity is described by assuming that some model coefficients are time-periodic, while the spatial heterogeneity is modeled by using a multi-patch structure and assuming that individuals travel among patches. We calculate the basic reproduction number [Formula: see text] and show that either the disease-free periodic solution is globally asymptotically stable if [Formula: see text] or the positive periodic solution is globally asymptotically stable if [Formula: see text]. Numerical simulations are conducted to confirm the analytical results and explore the effect of travel control on the disease prevalence.
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Affiliation(s)
- Daozhou Gao
- Francis I. Proctor Foundation for Research in Ophthalmology University of California, San Francisco San Francisco, CA 94143, USA
| | - Yijun Lou
- Department of Applied Mathematics The Hong Kong Polytechnic University Hung Hom, Kowloon, Hong Kong, China
| | - Shigui Ruan
- Department of Mathematics University of Miami Coral Gables, FL 33124, USA
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