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Owino EA. Kenya must wake up to the threat of cryptic Anopheles species and their impact on residual malaria transmission. J Vector Borne Dis 2024; 61:1-4. [PMID: 38648401 DOI: 10.4103/0972-9062.392264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Accepted: 08/17/2023] [Indexed: 04/25/2024] Open
Abstract
Malaria remains a major health problem in Kenya despite the huge efforts put in place to control it. The non-relenting malaria threat has partly been attributed to residual malaria transmission driven by vectors that cannot effectively be controlled by the two popularly applied control methods: long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS). Reports indicate that residual transmission is widely spread in areas where malaria is endemic. This could mean that the World Health Organization's vision of a world free of malaria remains a mirage as elimination and prevention of re-establishment of malaria are rendered unachievable. Amongst the major contributors to residual malaria transmission are cryptic rare species, species of mosquitoes that are morphologically indistinguishable, but isolated genetically, that have not been the focus of malaria control programs. Recent studies have reported extensive new Anopheles cryptic species believed to be involved in malaria transmission in Kenya. This underscores the need to understand these malaria vector species, their distribution and bionomics and their impact on malaria transmission. This article discusses reports of these cryptic species, their importance to malaria transmission, especially in the arid and semi-arid areas, and what can be done to mitigate the situation.
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2
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Suh PF, Elanga-Ndille E, Tchouakui M, Sandeu MM, Tagne D, Wondji C, Ndo C. Impact of insecticide resistance on malaria vector competence: a literature review. Malar J 2023; 22:19. [PMID: 36650503 PMCID: PMC9847052 DOI: 10.1186/s12936-023-04444-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Accepted: 01/04/2023] [Indexed: 01/18/2023] Open
Abstract
Since its first report in Anopheles mosquitoes in 1950s, insecticide resistance has spread very fast to most sub-Saharan African malaria-endemic countries, where it is predicted to seriously jeopardize the success of vector control efforts, leading to rebound of disease cases. Supported mainly by four mechanisms (metabolic resistance, target site resistance, cuticular resistance, and behavioural resistance), this phenomenon is associated with intrinsic changes in the resistant insect vectors that could influence development of invading Plasmodium parasites. A literature review was undertaken using Pubmed database to collect articles evaluating directly or indiretly the impact of insecticide resistance and the associated mechanisms on key determinants of malaria vector competence including sialome composition, anti-Plasmodium immunity, intestinal commensal microbiota, and mosquito longevity. Globally, the evidence gathered is contradictory even though the insecticide resistant vectors seem to be more permissive to Plasmodium infections. The actual body of knowledge on key factors to vectorial competence, such as the immunity and microbiota communities of the insecticide resistant vector is still very insufficient to definitively infer on the epidemiological importance of these vectors against the susceptible counterparts. More studies are needed to fill important knowledge gaps that could help predicting malaria epidemiology in a context where the selection and spread of insecticide resistant vectors is ongoing.
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Affiliation(s)
- Pierre Fongho Suh
- Department of Parasitology and Microbiology, Centre for Research in Infectious Diseases, P.O. Box 13591, Yaoundé, Cameroon
- Faculty of Sciences, University of Yaoundé I, P.O. Box 837, Yaoundé, Cameroon
| | - Emmanuel Elanga-Ndille
- Department of Medical Entomology, Centre for Research in Infectious Diseases, P.O. Box 13591, Yaoundé, Cameroon
| | - Magellan Tchouakui
- Department of Medical Entomology, Centre for Research in Infectious Diseases, P.O. Box 13591, Yaoundé, Cameroon
| | - Maurice Marcel Sandeu
- Department of Medical Entomology, Centre for Research in Infectious Diseases, P.O. Box 13591, Yaoundé, Cameroon
- Department of Microbiology and Infectious Diseases, School of Veterinary Medicine and Sciences, University of Ngaoundéré, P.O. Box 454, Ngaoundéré, Cameroon
| | - Darus Tagne
- Department of Parasitology and Microbiology, Centre for Research in Infectious Diseases, P.O. Box 13591, Yaoundé, Cameroon
- Faculty of Sciences, University of Douala, P.O. Box 24157, Douala, Cameroon
| | - Charles Wondji
- Department of Parasitology and Microbiology, Centre for Research in Infectious Diseases, P.O. Box 13591, Yaoundé, Cameroon
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Cyrille Ndo
- Department of Parasitology and Microbiology, Centre for Research in Infectious Diseases, P.O. Box 13591, Yaoundé, Cameroon.
- Department of Biological Sciences, Faculty of Medicine and Pharmaceutical Sciences, University of Douala, P.O. Box 24157, Douala, Cameroon.
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3
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Bohounton RB, Djogbénou LS, Djihinto OY, Dedome OSL, Sovegnon PM, Barea B, Adomou A, Villeneuve P, Tchobo FP. Chemical composition and the insecticidal activity of Aeollanthus pubescens leaf essential oil against Anopheles gambiae sensu stricto. Parasit Vectors 2021; 14:518. [PMID: 34620224 PMCID: PMC8499547 DOI: 10.1186/s13071-021-05012-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2021] [Accepted: 09/12/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The excessive use of synthetic insecticides is responsible for many cases of resistance in insects. Therefore, the use of natural molecules of ecological interest with insecticidal properties is an alternative approach to the use of synthetic insecticides. The aim of this study is to investigating the larvicidal and adulticidal activity and the chemical composition of the essential oil of Aeollanthus pubescens on the major malaria vector, Anopheles gambiae. METHODS Three reference strains of Anopheles gambiae sensu stricto (Kisumu, Kiskdr and Acerkis) were used in this study. The leaves of A. pubescens were collected in southern Benin. The standard World Health Organisation (WHO) guidelines for larvicide evaluation were used, and the chemical composition of the essential oil was analysed by gas chromatography coupled to mass spectrometry. Adult mosquitoes of each strain were exposed to pieces of net coated with the essential oil for 3 min using the WHO cone bioassay method. Probit regression analysis was used to determine the concentrations that would kill 50 and 95% of each test population (LC50, LC95) and the knockdown time for 50 and 95% of each test population (KDT50, and KDT95). The difference between the mortality-dose regressions for the different strains was analysed using the likelihood ratio test (LRT). The log-rank test was performed to evaluate the difference in survival between the strains. RESULTS A total of 14 components were identified, accounting for 98.3% of total oil content. The major components were carvacrol (51.1%), thymyle acetate (14.0%) and ɣ-terpinene (10.6%). The essential oil showed larvicidal properties on the Kisumu, Acerkis and Kiskdr strains, with LC50 of 29.6, 22.9 and 28.4 ppm, respectively. With pieces of netting treated at 165 µg/cm2, the KDT50 of both Acerkis (1.71 s; Z = 3.34, P < 0.001) and Kiskdr (2.67 s; Z = 3.49, P < 0.001) individuals were significantly lower than that of Kisumu (3.8 s). The lifespan of the three mosquito strains decreased to 1 day for Kisumu (χ2 = 99, df = 1, P < 0.001), 2 days for Acerkis (χ2 = 117, df = 1, P < 0.001) and 3 days for Kiskdr (χ2 = 96.9, df = 1, P < 0.001). CONCLUSION Our findings show that A. pubescens essential oil has larvicide and adulticide properties against the malaria vector An. gambiae sensu stricto, suggesting that this essential oil may be a potential candidate for the control of the resistant malaria-transmitting vectors.
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Affiliation(s)
- Roméo Barnabé Bohounton
- Laboratory of Study and Research of Applied Chemistry, Polytechnic School of Abomey-Calavi, Cotonou, Benin
- Tropical Infectious Diseases Research Centre (TIDRC), University of Abomey Calavi, Abomey-Calavi, Benin
| | - Luc Salako Djogbénou
- Tropical Infectious Diseases Research Centre (TIDRC), University of Abomey Calavi, Abomey-Calavi, Benin
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK
| | | | | | - Pierre Marie Sovegnon
- Tropical Infectious Diseases Research Centre (TIDRC), University of Abomey Calavi, Abomey-Calavi, Benin
| | | | - Aristide Adomou
- Laboratoire de Botanique Et Écologie Végétale (LaBEV), Faculté Des Sciences Et Techniques (FAST), University of Abomey-Calavi, Cotonou, Benin
| | | | - Fidèle Paul Tchobo
- Laboratory of Study and Research of Applied Chemistry, Polytechnic School of Abomey-Calavi, Cotonou, Benin
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4
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Couper LI, Farner JE, Caldwell JM, Childs ML, Harris MJ, Kirk DG, Nova N, Shocket M, Skinner EB, Uricchio LH, Exposito-Alonso M, Mordecai EA. How will mosquitoes adapt to climate warming? eLife 2021; 10:69630. [PMID: 34402424 PMCID: PMC8370766 DOI: 10.7554/elife.69630] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Accepted: 07/13/2021] [Indexed: 12/14/2022] Open
Abstract
The potential for adaptive evolution to enable species persistence under a changing climate is one of the most important questions for understanding impacts of future climate change. Climate adaptation may be particularly likely for short-lived ectotherms, including many pest, pathogen, and vector species. For these taxa, estimating climate adaptive potential is critical for accurate predictive modeling and public health preparedness. Here, we demonstrate how a simple theoretical framework used in conservation biology-evolutionary rescue models-can be used to investigate the potential for climate adaptation in these taxa, using mosquito thermal adaptation as a focal case. Synthesizing current evidence, we find that short mosquito generation times, high population growth rates, and strong temperature-imposed selection favor thermal adaptation. However, knowledge gaps about the extent of phenotypic and genotypic variation in thermal tolerance within mosquito populations, the environmental sensitivity of selection, and the role of phenotypic plasticity constrain our ability to make more precise estimates. We describe how common garden and selection experiments can be used to fill these data gaps. Lastly, we investigate the consequences of mosquito climate adaptation on disease transmission using Aedes aegypti-transmitted dengue virus in Northern Brazil as a case study. The approach outlined here can be applied to any disease vector or pest species and type of environmental change.
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Affiliation(s)
- Lisa I Couper
- Department of Biology, Stanford University, Stanford, United States
| | | | - Jamie M Caldwell
- Department of Biology, Stanford University, Stanford, United States.,Department of Biology, University of Hawaii at Manoa, Honolulu, United States
| | - Marissa L Childs
- Emmett Interdisciplinary Program in Environment and Resources, Stanford University, Stanford, United States
| | - Mallory J Harris
- Department of Biology, Stanford University, Stanford, United States
| | - Devin G Kirk
- Department of Biology, Stanford University, Stanford, United States.,Department of Zoology, University of Toronto, Toronto, Canada
| | - Nicole Nova
- Department of Biology, Stanford University, Stanford, United States
| | - Marta Shocket
- Department of Biology, Stanford University, Stanford, United States.,Department of Ecology and Evolutionary Biology, University of California Los Angeles, Los Angeles, United States
| | - Eloise B Skinner
- Department of Biology, Stanford University, Stanford, United States.,Environmental Futures Research Institute, Griffith University, Brisbane, Australia
| | - Lawrence H Uricchio
- Department of Integrative Biology, University of California, Berkeley, Berkeley, United States
| | - Moises Exposito-Alonso
- Department of Biology, Stanford University, Stanford, United States.,Department of Plant Biology, Carnegie Institution for Science, Stanford, United States
| | - Erin A Mordecai
- Department of Biology, Stanford University, Stanford, United States
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5
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Nkahe DL, Kopya E, Djiappi-Tchamen B, Toussile W, Sonhafouo-Chiana N, Kekeunou S, Mimpfoundi R, Awono-Ambene P, Wondji CS, Antonio-Nkondjio C. Fitness cost of insecticide resistance on the life-traits of a Anopheles coluzzii population from the city of Yaoundé, Cameroon. Wellcome Open Res 2020; 5:171. [PMID: 33029560 PMCID: PMC7525343 DOI: 10.12688/wellcomeopenres.16039.2] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/04/2020] [Indexed: 12/21/2022] Open
Abstract
Background: Pyrethroid resistance is rapidly expanding in An. gambiae s.l. populations across Sub-Saharan Africa. Yet there is still not enough information on the fitness cost of insecticide resistance . In the present study, the fitness cost of insecticide resistance on Anopheles coluzzii population from the city of Yaoundé was investigated. Methods: A resistant An. coluzzii colony was established from field collected mosquitoes resistant to both DDT and pyrethroid and selected for 12 generations with deltamethrin 0.05%. The Ngousso laboratory susceptible strain was used as control. A total of 100 females of each strain were blood fed and allowed for individual eggs laying, and then different life traits parameters such as fecundity, fertility, larval development time, emergence rate and longevity were measured. The TaqMan assay was used to screen for the presence of the L1014F and L1014S kdr mutations. Results: Field collected mosquitoes from the F0 generation had a mortality rate of 2.05% for DDT, 34.16% for permethrin and 50.23% for deltamethrin. The mortality rate of the F12 generation was 30.48% for deltamethrin, 1.25% for permethrin and 0% for DDT. The number of eggs laid per female was lower in the resistant colony compared to the susceptible (p <0.0001). Insecticide resistant larvae were found with a significantly long larval development time (10.61±0.33 days) compare to susceptible (7.57±0.35 days). The number of emerging females was significantly high in the susceptible group compared to the resistant . The adults lifespan was also significantly high for susceptible (21.73±1.19 days) compared to resistant (14.63±0.68 days). Only the L1014F- kdr allele was detected in resistant population.. Conclusion: The study suggests that pyrethroid resistance is likely associated with a high fitness cost on An.coluzzii populations. The addition of new tools targeting specifically larval stages could improve malaria vectors control and insecticide resistance management.
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Affiliation(s)
- Diane Leslie Nkahe
- Malaria Research Laboratory, OCEAC, Yaoundé, Centre, PO Box 288, Cameroon
- Department of Animal Biology, University of Yaoundé 1, Yaoundé, Cameroon
| | - Edmond Kopya
- Malaria Research Laboratory, OCEAC, Yaoundé, Centre, PO Box 288, Cameroon
- Department of Animal Biology, University of Yaoundé 1, Yaoundé, Cameroon
| | - Borel Djiappi-Tchamen
- Malaria Research Laboratory, OCEAC, Yaoundé, Centre, PO Box 288, Cameroon
- Department of Animal Biology, University of Dschang, Dschang, Cameroon
| | | | - Nadege Sonhafouo-Chiana
- Malaria Research Laboratory, OCEAC, Yaoundé, Centre, PO Box 288, Cameroon
- Faculty of Sciences, University of Buea, Buea, Cameroon
| | - Sevilor Kekeunou
- Department of Animal Biology, University of Yaoundé 1, Yaoundé, Cameroon
| | - Remy Mimpfoundi
- Department of Animal Biology, University of Yaoundé 1, Yaoundé, Cameroon
| | | | | | - Christophe Antonio-Nkondjio
- Malaria Research Laboratory, OCEAC, Yaoundé, Centre, PO Box 288, Cameroon
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
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6
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Nkahe DL, Kopya E, Djiappi-Tchamen B, Toussile W, Sonhafouo-Chiana N, Kekeunou S, Mimpfoundi R, Awono-Ambene P, Wondji CS, Antonio-Nkondjio C. Fitness cost of insecticide resistance on the life-traits of a Anopheles coluzzii population from the city of Yaoundé, Cameroon. Wellcome Open Res 2020; 5:171. [PMID: 33029560 PMCID: PMC7525343 DOI: 10.12688/wellcomeopenres.16039.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/10/2020] [Indexed: 08/03/2024] Open
Abstract
Background: Pyrethroid resistance is rapidly expanding in An. gambiae s.l. populations across Sub-Saharan Africa. Yet there is still not enough information on the fitness cost of insecticide resistance . In the present study, the fitness cost of insecticide resistance on Anopheles coluzzii population from the city of Yaoundé was investigated. Methods: A resistant An. coluzzii colony was established from field collected mosquitoes resistant to both DDT and pyrethroid and selected for 12 generations with deltamethrin 0.05%. The Ngousso laboratory susceptible strain was used as control. A total of 100 females of each strain were blood fed and allowed for individual eggs laying, and then different life traits parameters such as fecundity, fertility, larval development time, emergence rate and longevity were measured. The TaqMan assay was used to screen for the presence of the L1014F and L1014S kdr mutations. Results: Field collected mosquitoes from the F0 generation had a mortality rate of 2.05% for DDT, 34.16% for permethrin and 50.23% for deltamethrin. The mortality rate of the F12 generation was 30.48% for deltamethrin, 1.25% for permethrin and 0% for DDT. The number of eggs laid per female was lower in the resistant colony compared to the susceptible (p <0.0001). Insecticide resistant larvae were found with a significantly long larval development time (10.61±0.33 days) compare to susceptible (7.57±0.35 days). The number of emerging females was significantly high in the susceptible group compared to the resistant . The adults lifespan was also significantly high for susceptible (21.73±1.19 days) compared to resistant (14.63±0.68 days). Only the L1014F- kdr allele was detected in resistant population.. Conclusion: The study suggests that pyrethroid resistance is likely associated with a high fitness cost on An.coluzzii populations. The addition of new tools targeting specifically larval stages could improve malaria vectors control and insecticide resistance management.
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Affiliation(s)
- Diane Leslie Nkahe
- Malaria Research Laboratory, OCEAC, Yaoundé, Centre, PO Box 288, Cameroon
- Department of Animal Biology, University of Yaoundé 1, Yaoundé, Cameroon
| | - Edmond Kopya
- Malaria Research Laboratory, OCEAC, Yaoundé, Centre, PO Box 288, Cameroon
- Department of Animal Biology, University of Yaoundé 1, Yaoundé, Cameroon
| | - Borel Djiappi-Tchamen
- Malaria Research Laboratory, OCEAC, Yaoundé, Centre, PO Box 288, Cameroon
- Department of Animal Biology, University of Dschang, Dschang, Cameroon
| | | | - Nadege Sonhafouo-Chiana
- Malaria Research Laboratory, OCEAC, Yaoundé, Centre, PO Box 288, Cameroon
- Faculty of Sciences, University of Buea, Buea, Cameroon
| | - Sevilor Kekeunou
- Department of Animal Biology, University of Yaoundé 1, Yaoundé, Cameroon
| | - Remy Mimpfoundi
- Department of Animal Biology, University of Yaoundé 1, Yaoundé, Cameroon
| | | | | | - Christophe Antonio-Nkondjio
- Malaria Research Laboratory, OCEAC, Yaoundé, Centre, PO Box 288, Cameroon
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
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7
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Kerteszia cruzii and extra-Amazonian malaria in Brazil: Challenges due to climate change in the Atlantic Forest. INFECTION GENETICS AND EVOLUTION 2020; 85:104456. [PMID: 32668366 DOI: 10.1016/j.meegid.2020.104456] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2020] [Revised: 07/03/2020] [Accepted: 07/05/2020] [Indexed: 01/09/2023]
Abstract
Kerteszia cruzii is a sylvatic mosquito and the primary vector of Plasmodium spp., which can cause malaria in humans in areas outside the Amazon River basin in Brazil. Anthropic changes in the natural environments are the major drivers of massive deforestation and local climate change, with serious impacts on the dynamics of mosquito communities and on the risk of acquiring malaria. Considering the lack of information on the dynamics of malaria transmission in areas across the Atlantic Forest biome, where Ke. cruzii is the dominant vector, and the impact of climate drivers of malaria, the present study aimed to: (i) investigate the occurrence and survival rate of Ke. cruzii based on the distinct vegetation profiles found in areas across the coastal region of the Brazilian Atlantic Forest biome; (ii) estimate the extrinsic incubation period (EIP) and survival rates of P. vivax and P. falciparum parasites in Ke. cruzii under current and future scenarios. The potential distribution of Plasmodium spp. was estimated using simulation analyses under distinct scenarios of average temperature increases from 1 °C to 3.7 °C. Our results showed that two conditions are necessary to explain the occurrence and survival of Ke. cruzii: warm temperature and presence of the Atlantic Forest biome. Moreover, both Plasmodium species showed a tendency to decrease their EIP and increase their estimated survival rates in a scenario of higher temperature. Our findings support that the high-risk malaria areas may include the southern region of the distribution range of the Atlantic Forest biome in the coming years. Despite its limitations and assumptions, the present study provides robust evidence of areas with potential to be impacted by malaria incidence in a future scenario. These areas should be monitored in the next decades regarding the occurrence of the mosquito vector and the potential for malaria persistence and increased occurrence.
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8
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Suh E, Grossman MK, Waite JL, Dennington NL, Sherrard-Smith E, Churcher TS, Thomas MB. The influence of feeding behaviour and temperature on the capacity of mosquitoes to transmit malaria. Nat Ecol Evol 2020; 4:940-951. [PMID: 32367033 PMCID: PMC7334094 DOI: 10.1038/s41559-020-1182-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Accepted: 03/20/2020] [Indexed: 12/23/2022]
Abstract
Insecticide-treated bed nets reduce malaria transmission by limiting contact between mosquito vectors and human hosts when mosquitoes feed during the night. However, malaria vectors can also feed in the early evening and in the morning when people are not protected. Here, we explored how the timing of blood feeding interacts with environmental temperature to influence the capacity of Anopheles mosquitoes to transmit the human malaria parasite Plasmodium falciparum. In laboratory experiments, we found no effect of biting time itself on the proportion of mosquitoes that became infectious (vector competence) at constant temperature. However, when mosquitoes were maintained under more realistic fluctuating temperatures, there was a significant increase in competence for mosquitoes feeding in the evening (18:00), and a significant reduction in competence for those feeding in the morning (06:00), relative to those feeding at midnight (00:00). These effects appear to be due to thermal sensitivity of malaria parasites during the initial stages of parasite development within the mosquito, and the fact that mosquitoes feeding in the evening experience cooling temperatures during the night, whereas mosquitoes feeding in the morning quickly experience warming temperatures that are inhibitory to parasite establishment. A transmission dynamics model illustrates that such differences in competence could have important implications for malaria prevalence, the extent of transmission that persists in the presence of bed nets, and the epidemiological impact of behavioural resistance. These results indicate that the interaction of temperature and feeding behaviour could be a major ecological determinant of the vectorial capacity of malaria mosquitoes.
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Affiliation(s)
- Eunho Suh
- Center for Infectious Disease Dynamics, Department of Entomology, Penn State University, University Park, PA, USA.
| | - Marissa K Grossman
- Center for Infectious Disease Dynamics, Department of Entomology, Penn State University, University Park, PA, USA
| | - Jessica L Waite
- Center for Infectious Disease Dynamics, Department of Entomology, Penn State University, University Park, PA, USA.,Green Mountain Antibodies, Burlington, VT, USA
| | - Nina L Dennington
- Center for Infectious Disease Dynamics, Department of Entomology, Penn State University, University Park, PA, USA
| | - Ellie Sherrard-Smith
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, UK
| | - Thomas S Churcher
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, UK
| | - Matthew B Thomas
- Center for Infectious Disease Dynamics, Department of Entomology, Penn State University, University Park, PA, USA
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9
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Tchakounte A, Tchouakui M, Mu-Chun C, Tchapga W, Kopia E, Soh PT, Njiokou F, Riveron JM, Wondji CS. Exposure to the insecticide-treated bednet PermaNet 2.0 reduces the longevity of the wild African malaria vector Anopheles funestus but GSTe2-resistant mosquitoes live longer. PLoS One 2019; 14:e0213949. [PMID: 30870507 PMCID: PMC6417719 DOI: 10.1371/journal.pone.0213949] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 03/04/2019] [Indexed: 01/25/2023] Open
Abstract
BACKGROUND Despite the increased report of insecticide resistance in malaria vectors, its impact on mosquito's life-traits after exposure to insecticide-treated nets remains under investigated. Here, we assessed the effects of exposure to PermaNet 2.0 on several life traits of An. gambiae s.l. and An. funestus s.l. field mosquitoes in Cameroon. METHODOLOGY Female Anopheles mosquitoes were collected indoor using electric aspirators in southern Cameroon (Obout) in 2016. After assessing the resistance status of F1 from the field collected-mosquitoes, progeny of the first generation (An. funestus s.l.) and seventh generation (An. gambiae s.l.) were used to assess the long-term effect of exposure to PermaNet 2.0 on several life-traits of these vectors (longevity, blood feeding ability, fecundity and fertility) in comparison to untreated net. In addition, the L119F-GSTe2 mutation associated with DDT/pyrethroids resistance in An. funestus was genotyped to assess its association with increased life-span post-exposure. PRINCIPAL FINDINGS Both An. funestus and An. gambiae were resistant to pyrethroids and DDT with a greater level in the latter. Pyrethroid-only nets PermaNet 2.0 (17.5% mortality) and Olyset (0% mortality) exhibited a significantly reduced efficacy against An. funestus in contrast to a greater efficacy for PBO-based Nets Olyset Plus (65% mortality), PermaNet 3.0 top (100% mortality). In both species, mosquitoes that survived exposure to PermaNet 2.0 exhibited a significantly reduced longevity than those non-exposed (6.95 days vs 12.46 for An. funestus P<0.001; 8.87 vs 11.25 days for An. gambiae; P<0.001). However, no significant difference was observed for blood feeding and fecundity in both species. In addition, molecular analysis of the L119F-GSTe2 mutation revealed that this mutation is associated with an increase in the chance of surviving after exposure to this net in An. funestus. CONCLUSIONS These results show that although the PermaNet 2.0 presents a reduced efficacy against resistant populations, it remains efficient after exposure by reducing the life expectancy of the vectors which could contribute in the reduction of malaria incidence.
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Affiliation(s)
- Ange Tchakounte
- Centre for Research in Infectious Diseases (CRID), Yaoundé, Cameroon
- Research Unit LSTM/OCEAC, Yaoundé, Cameroon
- Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé, Yaoundé, Cameroon
| | - Magellan Tchouakui
- Centre for Research in Infectious Diseases (CRID), Yaoundé, Cameroon
- Research Unit LSTM/OCEAC, Yaoundé, Cameroon
- Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé, Yaoundé, Cameroon
| | - Chiang Mu-Chun
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - Williams Tchapga
- Centre for Research in Infectious Diseases (CRID), Yaoundé, Cameroon
- Research Unit LSTM/OCEAC, Yaoundé, Cameroon
| | - Edmond Kopia
- Research Unit LSTM/OCEAC, Yaoundé, Cameroon
- Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé, Yaoundé, Cameroon
| | - Patrice Takam Soh
- Department of Mathematics, Faculty of Science, University of Yaoundé, Yaoundé, Cameroon
| | - Flobert Njiokou
- Centre for Research in Infectious Diseases (CRID), Yaoundé, Cameroon
- Research Unit LSTM/OCEAC, Yaoundé, Cameroon
| | - Jacob Miranda Riveron
- Centre for Research in Infectious Diseases (CRID), Yaoundé, Cameroon
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - Charles S. Wondji
- Centre for Research in Infectious Diseases (CRID), Yaoundé, Cameroon
- Research Unit LSTM/OCEAC, Yaoundé, Cameroon
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
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10
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Huijben S, Paaijmans KP. Putting evolution in elimination: Winning our ongoing battle with evolving malaria mosquitoes and parasites. Evol Appl 2018; 11:415-430. [PMID: 29636796 PMCID: PMC5891050 DOI: 10.1111/eva.12530] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 08/01/2017] [Indexed: 12/17/2022] Open
Abstract
Since 2000, the world has made significant progress in reducing malaria morbidity and mortality, and several countries in Africa, South America and South-East Asia are working hard to eliminate the disease. These elimination efforts continue to rely heavily on antimalarial drugs and insecticide-based interventions, which remain the cornerstones of malaria treatment and prevention. However, resistance has emerged against nearly every antimalarial drug and insecticide that is available. In this review we discuss the evolutionary consequences of the way we currently implement antimalarial interventions, which is leading to resistance and may ultimately lead to control failure, but also how evolutionary principles can be applied to extend the lifespan of current and novel interventions. A greater understanding of the general evolutionary principles that are at the core of emerging resistance is urgently needed if we are to develop improved resistance management strategies with the ultimate goal to achieve a malaria-free world.
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Affiliation(s)
- Silvie Huijben
- ISGlobalBarcelona Ctr. Int. Health Res. (CRESIB)Hospital Clínic ‐ Universitat de BarcelonaBarcelonaSpain
| | - Krijn P. Paaijmans
- ISGlobalBarcelona Ctr. Int. Health Res. (CRESIB)Hospital Clínic ‐ Universitat de BarcelonaBarcelonaSpain
- Centro de Investigação em Saúde de ManhiçaMaputoMozambique
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11
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Smith TA, Chitnis N, Penny M, Tanner M. Malaria Modeling in the Era of Eradication. Cold Spring Harb Perspect Med 2017; 7:cshperspect.a025460. [PMID: 28003280 DOI: 10.1101/cshperspect.a025460] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Mathematical models provide the essential basis of rational research and development strategies in malaria, informing the choice of which technologies to target, which deployment strategies to consider, and which populations to focus on. The Internet and remote sensing technologies also enable assembly of ever more relevant field data. Together with supercomputing technology, this has made available timely descriptions of the geography of malaria transmission and disease across the world and made it possible for policy and planning to be informed by detailed simulations of the potential impact of intervention programs. These information technology advances do not replace the basic understanding of the dynamics of malaria transmission that should be embedded in the thinking of anyone planning malaria interventions. The appropriate use of modeling may determine whether we are living in an era of hubris or indeed in an age of eradication.
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Affiliation(s)
- Thomas A Smith
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel CH 4002, Switzerland; and University of Basel, Basel CH 4001, Switzerland
| | - Nakul Chitnis
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel CH 4002, Switzerland; and University of Basel, Basel CH 4001, Switzerland
| | - Melissa Penny
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel CH 4002, Switzerland; and University of Basel, Basel CH 4001, Switzerland
| | - Marcel Tanner
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel CH 4002, Switzerland; and University of Basel, Basel CH 4001, Switzerland
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12
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Kibuthu TW, Njenga SM, Mbugua AK, Muturi EJ. Agricultural chemicals: life changer for mosquito vectors in agricultural landscapes? Parasit Vectors 2016; 9:500. [PMID: 27624456 PMCID: PMC5022241 DOI: 10.1186/s13071-016-1788-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Accepted: 09/02/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Although many mosquito species develop within agricultural landscapes where they are potentially exposed to agricultural chemicals (fertilizers and pesticides), the effects of these chemicals on mosquito biology remain poorly understood. This study investigated the effects of sublethal concentrations of four agricultural chemicals on the life history traits of Anopheles arabiensis and Culex quinquefasciatus mosquitoes. METHODS Field and laboratory experiments were conducted to examine how sublethal concentrations of four agricultural chemicals: an insecticide (cypermethrin), a herbicide (glyphosate), and two nitrogenous fertilizers (ammonium sulfate and diammonium phosphate) alter oviposition site selection, emergence rates, development time, adult body size, and longevity of An. arabiensis and Cx. quinquefasciatus. RESULTS Both mosquito species had preference to oviposit in fertilizer treatments relative to pesticide treatments. Emergence rates for An. arabiensis were significantly higher in the control and ammonium sulfate treatments compared to cypermethrin treatment, while emergence rates for Cx. quinquefasciatus were significantly higher in the diammonium phosphate treatment compared to glyphosate and cypermethrin treatments. For both mosquito species, individuals from the ammonium sulfate and diammonium phosphate treatments took significantly longer time to develop compared to those from cypermethrin and glyphosate treatments. Although not always significant, males and females of both mosquito species tended to be smaller in the ammonium sulfate and diammonium phosphate treatments compared to cypermethrin and glyphosate treatments. There was no significant effect of the agrochemical treatments on the longevity of either mosquito species. CONCLUSIONS These results demonstrate that the widespread use of agricultural chemicals to enhance crop production can have unexpected effects on the spatial distribution and abundance of mosquito vectors of malaria and lymphatic filariasis.
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Affiliation(s)
- Tabitha W. Kibuthu
- Institute of Tropical Medicine, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya
| | - Sammy M. Njenga
- Eastern and Southern Africa Centre of International Parasite Control, Kenya Medical Research Institute, Nairobi, Kenya
| | - Amos K. Mbugua
- College of Health Sciences, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya
| | - Ephantus J. Muturi
- Illinois Natural History Survey, Prairie Research Institute, University of Illinois, Champaign, USA
- Present Address: U.S.D.A., Agricultural Research Service, National Center for Agricultural Utilization Research, Crop Bioprotection Research Unit, 1815 N. University St., Peoria, IL 61604 USA
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13
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Delayed mortality effects cut the malaria transmission potential of insecticide-resistant mosquitoes. Proc Natl Acad Sci U S A 2016; 113:8975-80. [PMID: 27402740 DOI: 10.1073/pnas.1603431113] [Citation(s) in RCA: 81] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Malaria transmission has been substantially reduced across Africa through the distribution of long-lasting insecticidal nets (LLINs). However, the emergence of insecticide resistance within mosquito vectors risks jeopardizing the future efficacy of this control strategy. The severity of this threat is uncertain because the consequences of resistance for mosquito fitness are poorly understood: while resistant mosquitoes are no longer immediately killed upon contact with LLINs, their transmission potential may be curtailed because of longer-term fitness costs that persist beyond the first 24 h after exposure. Here, we used a Bayesian state-space model to quantify the immediate (within 24 h of exposure) and delayed (>24 h after exposure) impact of insecticides on daily survival and malaria transmission potential of moderately and highly resistant laboratory populations of the major African malaria vector Anopheles gambiae Contact with LLINs reduced the immediate survival of moderately and highly resistant An. gambiae strains by 60-100% and 3-61%, respectively, and delayed mortality impacts occurring beyond the first 24 h after exposure further reduced their overall life spans by nearly one-half. In total, insecticide exposure was predicted to reduce the lifetime malaria transmission potential of insecticide-resistant vectors by two-thirds, with delayed effects accounting for at least one-half of this reduction. The existence of substantial, previously unreported, delayed mortality effects within highly resistant malaria vectors following exposure to insecticides does not diminish the threat of growing resistance, but posits an explanation for the apparent paradox of continued LLIN effectiveness in the presence of high insecticide resistance.
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14
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Russell TL, Beebe NW, Bugoro H, Apairamo A, Collins FH, Cooper RD, Lobo NF, Burkot TR. Anopheles farauti is a homogeneous population that blood feeds early and outdoors in the Solomon Islands. Malar J 2016; 15:151. [PMID: 26960327 PMCID: PMC4784415 DOI: 10.1186/s12936-016-1194-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 02/26/2016] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND In the 1970s, Anopheles farauti in the Solomon Island responded to indoor residual spraying with DDT by increasingly feeding more outdoors and earlier in the evening. Although long-lasting insecticidal nets (LLINs) are now the primary malaria vector control intervention in the Solomon Islands, only a small proportion of An. farauti still seek blood meals indoors and late at night where they are vulnerable to being killed by contract with the insecticides in LLINs. The effectiveness of LLINs and indoor residual spraying (IRS) in controlling malaria transmission where the vectors are exophagic and early biting will depend on whether the predominant outdoor or early biting phenotypes are associated with a subpopulation of the vectors present. METHODS Mark-release-recapture experiments were conducted in the Solomon Islands to determine if individual An. farauti repeat the same behaviours over successive feeding cycles. The two behavioural phenotypes examined were those on which the WHO recommended malaria vector control strategies, LLINs and IRS, depend: indoor and late night biting. RESULTS Evidence was found for An. farauti being a single population regarding time (early evening or late night) and location (indoor or outdoor) of blood feeding. Individual An. farauti did not consistently repeat behavioural phenotypes expressed for blood feeding (e.g., while most mosquitoes that fed early and outdoors, and would repeat those behaviours, some fed late at night or indoors in the next feeding cycle). CONCLUSIONS The finding that An. farauti is a homogeneous population is significant, because during the multiple feeding cycles required to complete the extrinsic incubation period, many individual female anophelines will enter houses late at night and be exposed to the insecticides used in LLINs or IRS. This explains, in part, the control that LLINs and IRS have exerted against a predominantly outdoor feeding vector, such as An. farauti. These findings may be relevant to many of the outdoor feeding vectors that dominate transmission in much of the malaria endemic world and justifies continued use of LLINs. However, the population-level tendency of mosquitoes to feed outdoors and early in the evening does require complementary interventions to accelerate malaria control towards elimination.
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Affiliation(s)
- Tanya L Russell
- Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, QLD, 4870, Australia.
| | - Nigel W Beebe
- School of Biological Sciences, University of Queensland, St. Lucia, QLD, 4068, Australia.
- CSIRO, Dutton Park, Brisbane, QLD, 4102, Australia.
| | - Hugo Bugoro
- National Vector Borne Disease Control Programme, Ministry of Health, Honiara, Solomon Islands.
| | - Allan Apairamo
- National Vector Borne Disease Control Programme, Ministry of Health, Honiara, Solomon Islands.
| | - Frank H Collins
- Department of Biological Sciences, Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, 46556, USA.
| | - Robert D Cooper
- Australian Army Malaria Institute, Gallipoli Barracks, Enoggera, 4052, Australia.
| | - Neil F Lobo
- Department of Biological Sciences, Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, 46556, USA.
| | - Thomas R Burkot
- Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, QLD, 4870, Australia.
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15
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Stone C, Chitnis N, Gross K. Environmental influences on mosquito foraging and integrated vector management can delay the evolution of behavioral resistance. Evol Appl 2016; 9:502-17. [PMID: 26989441 PMCID: PMC4778105 DOI: 10.1111/eva.12354] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 12/21/2015] [Indexed: 11/29/2022] Open
Abstract
Along with the scaled‐up distribution of long‐lasting insecticidal nets for malaria control has become concern about insecticide resistance. A related concern regards the evolution of host‐seeking periodicity from the nocturnal to the crepuscular periods of the day. Why we observe such shifts in some areas but not others and which methods could prove useful in managing such behavioral resistance remain open questions. We developed a foraging model to explore whether environmental conditions affect the evolution of behavioral resistance. We looked at the role of the abundance of blood hosts and nectar sources and investigated the potential of attractive toxic sugar baits for integrated control. Higher encounter rates with hosts and nectar sources allowed behaviorally resistant populations to persist at higher levels of bed net coverage. Whereas higher encounter rates with nectar increased the threshold where resistance emerged, higher encounter rates of hosts lowered this threshold. Adding sugar baits lowered the coverage level of bed nets required to eliminate the vector population. In certain environments, using lower bed net coverage levels together with toxic sugar baits may delay or prevent the evolution of behavioral resistance. Designing sustainable control strategies will depend on an understanding of vector behavior expressed in local environmental conditions.
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Affiliation(s)
- Chris Stone
- Department of Statistics North Carolina State University Raleigh NC USA
| | - Nakul Chitnis
- Swiss Tropical and Public Health Institute Basel Switzerland; University of Basel Basel Switzerland
| | - Kevin Gross
- Department of Statistics North Carolina State University Raleigh NC USA
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16
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Killeen GF. Characterizing, controlling and eliminating residual malaria transmission. Malar J 2014; 13:330. [PMID: 25149656 PMCID: PMC4159526 DOI: 10.1186/1475-2875-13-330] [Citation(s) in RCA: 303] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 08/16/2014] [Indexed: 12/02/2022] Open
Abstract
Long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) interventions can reduce malaria transmission by targeting mosquitoes when they feed upon sleeping humans and/or rest inside houses, livestock shelters or other man-made structures. However, many malaria vector species can maintain robust transmission, despite high coverage of LLINs/IRS containing insecticides to which they are physiologically fully susceptible, because they exhibit one or more behaviours that define the biological limits of achievable impact with these interventions: (1) Natural or insecticide-induced avoidance of contact with treated surfaces within houses and early exit from them, thus minimizing exposure hazard of vectors which feed indoors upon humans; (2) Feeding upon humans when they are active and unprotected outdoors, thereby attenuating personal protection and any consequent community-wide suppression of transmission; (3) Feeding upon animals, thus minimizing contact with insecticides targeted at humans or houses; (4) Resting outdoors, away from insecticide-treated surfaces of nets, walls and roofs. Residual malaria transmission is, therefore, defined as all forms of transmission that can persist after achieving full universal coverage with effective LLINs and/or IRS containing active ingredients to which local vector populations are fully susceptible. Residual transmission is sufficiently intense across most of the tropics to render malaria elimination infeasible without new or improved vector control methods. Many novel or improved vector control strategies to address residual transmission are emerging that either: (1) Enhance control of adult vectors that enter houses to feed and/or rest by killing, repelling or excluding them; (2) Kill or repel adult mosquitoes when they attack people outdoors; (3) Kill adult mosquitoes when they attack livestock; (4) Kill adult mosquitoes when they feed upon sugar or; (5) Kill immature mosquitoes in aquatic habitats. To date, none of these options has sufficient supporting evidence to justify full-scale programmatic implementation. Concerted investment in their rigorous selection, development and evaluation is required over the coming decade to enable control and, ultimately, elimination of residual malaria transmission. In the meantime, national programmes may assess options for addressing residual transmission under programmatic conditions through pilot studies with strong monitoring, evaluation and operational research components, similar to the Onchocerciasis Control Programme.
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Affiliation(s)
- Gerry F Killeen
- Ifakara Health Institute, Environmental Health and Ecological Sciences Thematic Group, Ifakara, Morogoro, United Republic of Tanzania.
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17
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Guerra CA, Reiner RC, Perkins TA, Lindsay SW, Midega JT, Brady OJ, Barker CM, Reisen WK, Harrington LC, Takken W, Kitron U, Lloyd AL, Hay SI, Scott TW, Smith DL. A global assembly of adult female mosquito mark-release-recapture data to inform the control of mosquito-borne pathogens. Parasit Vectors 2014; 7:276. [PMID: 24946878 PMCID: PMC4067626 DOI: 10.1186/1756-3305-7-276] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Accepted: 06/11/2014] [Indexed: 11/26/2022] Open
Abstract
Background Pathogen transmission by mosquitos is known to be highly sensitive to mosquito bionomic parameters. Mosquito mark-release-recapture (MMRR) experiments are a standard method for estimating such parameters including dispersal, population size and density, survival, blood feeding frequency and blood meal host preferences. Methods We assembled a comprehensive database describing adult female MMRR experiments. Bibliographic searches were used to build a digital library of MMRR studies and selected data describing the reported outcomes were extracted. Results The resulting database contained 774 unique adult female MMRR experiments involving 58 vector mosquito species from the three main genera of importance to human health: Aedes, Anopheles and Culex. Crude examination of these data revealed patterns associated with geography as well as mosquito genus, consistent with bionomics varying by species-specific life history and ecological context. Recapture success varied considerably and was significantly different amongst genera, with 8, 4 and 1% of adult females recaptured for Aedes, Anopheles and Culex species, respectively. A large proportion of experiments (59%) investigated dispersal and survival and many allowed disaggregation of the release and recapture data. Geographic coverage was limited to just 143 localities around the world. Conclusions This MMRR database is a substantial contribution to the compilation of global data that can be used to better inform basic research and public health interventions, to identify and fill knowledge gaps and to enrich theory and evidence-based ecological and epidemiological studies of mosquito vectors, pathogen transmission and disease prevention. The database revealed limited geographic coverage and a relative scarcity of information for vector species of substantial public health relevance. It represents, however, a wealth of entomological information not previously compiled and of particular interest for mosquito-borne pathogen transmission models.
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Affiliation(s)
- Carlos A Guerra
- Fogarty International Center, National Institutes of Health, Bethesda, MD, USA.
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18
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Eckhoff P. Mathematical models of within-host and transmission dynamics to determine effects of malaria interventions in a variety of transmission settings. Am J Trop Med Hyg 2013; 88:817-827. [PMID: 23589530 PMCID: PMC3752743 DOI: 10.4269/ajtmh.12-0007] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
A model for Anopheles population dynamics and malaria transmission is combined with a within-host dynamics microsolver to study baseline transmission, the effects of seasonality, and the impact of interventions. The Garki Project is recreated in simulation of the pre-intervention baseline and the different combinations of interventions deployed. Modifications are introduced, and longer project duration, extension of dry-season spraying, and transmission-blocking vaccines together achieve local elimination in some conditions. A variety of interventions are simulated in transmission settings that vary in transmission intensity and underlying seasonality. Adding vaccines to existing vector control efforts extends the ability to achieve elimination to higher baseline transmission and less favorable vector behavior. If one species of the Anopheles gambiae species complex feeds disproportionately outdoors for a given complex average behavior, vector control impacts are less than for a single species. Non-zero dry-season transmission limits seasonal oscillation in parasite dynamics and impact of wet-season interventions.
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Affiliation(s)
- Philip Eckhoff
- *Address correspondence to Philip Eckhoff, Intellectual Ventures Laboratory, 1575 132nd Avenue NE, Bellevue, WA 98004. E-mail:
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19
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Gatton ML, Chitnis N, Churcher T, Donnelly MJ, Ghani AC, Godfray HCJ, Gould F, Hastings I, Marshall J, Ranson H, Rowland M, Shaman J, Lindsay SW. The importance of mosquito behavioural adaptations to malaria control in Africa. Evolution 2013; 67:1218-30. [PMID: 23550770 PMCID: PMC3655544 DOI: 10.1111/evo.12063] [Citation(s) in RCA: 199] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Accepted: 01/12/2013] [Indexed: 01/25/2023]
Abstract
Over the past decade the use of long-lasting insecticidal nets (LLINs), in combination with improved drug therapies, indoor residual spraying (IRS), and better health infrastructure, has helped reduce malaria in many African countries for the first time in a generation. However, insecticide resistance in the vector is an evolving threat to these gains. We review emerging and historical data on behavioral resistance in response to LLINs and IRS. Overall the current literature suggests behavioral and species changes may be emerging, but the data are sparse and, at times unconvincing. However, preliminary modeling has demonstrated that behavioral resistance could have significant impacts on the effectiveness of malaria control. We propose seven recommendations to improve understanding of resistance in malaria vectors. Determining the public health impact of physiological and behavioral insecticide resistance is an urgent priority if we are to maintain the significant gains made in reducing malaria morbidity and mortality.
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Affiliation(s)
- Michelle L Gatton
- Fogarty International Center, National Institutes of Health, Bethesda, Maryland 20892-2220, USA.
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20
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Lyimo IN, Haydon DT, Russell TL, Mbina KF, Daraja AA, Mbehela EM, Reeve R, Ferguson HM. The impact of host species and vector control measures on the fitness of African malaria vectors. Proc Biol Sci 2013; 280:20122823. [PMID: 23303548 DOI: 10.1098/rspb.2012.2823] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Many malaria vector mosquitoes in Africa have an extreme preference for feeding on humans. This specialization allows them to sustain much higher levels of transmission than elsewhere, but there is little understanding of the evolutionary forces that drive this behaviour. In Tanzania, we used a semi-field system to test whether the well-documented preferences of the vectors, Anopheles arabiensis and Anopheles gambiae sensu stricto (s.s.) for cattle and humans, respectively, are predicted by the fitness they obtain from host-seeking on these species relative to other available hosts. Mosquito fitness was contrasted, when humans were fully exposed and when they were protected by a typical bednet. The fitness of both vectors varied between host species. The predicted relationship between host preference and fitness was confirmed in An. arabiensis, but not in An. gambiae s.s., whose fitness was similar on humans and other mammals. Use of typical, imperfect bednets generated only minor reductions in An. gambiae s.s. feeding success and fitness on humans, but was predicted to generate a significant reduction in the lifetime reproductive success of An. arabiensis on humans relative to cows. This supports the hypothesis that such human-protective measures could additionally benefit malaria control by increasing selection for zoophily in vectors.
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Affiliation(s)
- Issa N Lyimo
- Environmental Science Thematic Group, Ifakara Health Institute, PO Box 53, Ifakara, Tanzania.
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Does Cattle Milieu Provide a Potential Point to Target Wild Exophilic Anopheles arabiensis (Diptera: Culicidae) with Entomopathogenic Fungus? A Bioinsecticide Zooprophylaxis Strategy for Vector Control. J Parasitol Res 2012; 2012:280583. [PMID: 22934152 PMCID: PMC3425831 DOI: 10.1155/2012/280583] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Accepted: 06/30/2012] [Indexed: 11/17/2022] Open
Abstract
Background. Anopheles arabiensis is increasingly dominating malaria transmission in Africa. The exophagy in mosquitoes threatens the effectiveness of indoor vector control strategies. This study aimed to evaluate the effectiveness of fungus against An. arabiensis when applied on cattle and their environments. Methods. Experiments were conducted under semi-field and small-scale field conditions within Kilombero valley. The semi-field reared females of 5–7 days old An. arabiensis were exposed to fungus-treated and untreated calf. Further, wild An. arabiensis were exposed to fungus-treated calves, mud-huts, and their controls. Mosquitoes were recaptured the next morning and proportion fed, infected, and survived were evaluated. Experiments were replicated three times using different individuals of calves. Results. A high proportion of An. arabiensis was fed on calves (>0.90) and become infected (0.94) while resting on fungus-treated mud walls than on other surfaces. However, fungus treatments reduced fecundity and survival of mosquitoes.
Conclusion. This study demonstrates for the first time the potential of cattle and their milieu for controlling An. arabiensis. Most of An. arabiensis were fed and infected while resting on fungus-treated mud walls than on other surfaces. Fungus treatments reduced fecundity and survival of mosquitoes. These results suggest deployment of bioinsecticide zooprophylaxis against exophilic An. arabiensis.
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