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Oke CE, Ingham VA, Walling CA, Reece SE. Vector control: agents of selection on malaria parasites? Trends Parasitol 2022; 38:890-903. [PMID: 35981937 DOI: 10.1016/j.pt.2022.07.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 06/30/2022] [Accepted: 07/21/2022] [Indexed: 10/15/2022]
Abstract
Insect vectors are responsible for spreading many infectious diseases, yet interactions between pathogens/parasites and insect vectors remain poorly understood. Filling this knowledge gap matters because vectors are evolving in response to the deployment of vector control tools (VCTs). Yet, whilst the evolutionary responses of vectors to VCTs are being carefully monitored, the knock-on consequences for parasite evolution have been overlooked. By examining how mosquito responses to VCTs impact upon malaria parasite ecology, we derive a framework for predicting parasite responses. Understanding how VCTs affect the selection pressures imposed on parasites could help to mitigate against parasite evolution that leads to unfavourable epidemiological outcomes. Furthermore, anticipating parasite evolution will inform monitoring strategies for VCT programmes as well as uncovering novel VCT strategies.
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Affiliation(s)
- Catherine E Oke
- Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh, EH9 3FL, UK.
| | - Victoria A Ingham
- Centre for Infectious Diseases, Parasitology Unit, Heidelberg University Hospital, Im Neuenheimer Feld 324, 69210 Heidelberg, Germany
| | - Craig A Walling
- Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh, EH9 3FL, UK
| | - Sarah E Reece
- Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh, EH9 3FL, UK; Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, EH9 3FL, UK
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2
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Barreaux P, Koella JC, N'Guessan R, Thomas MB. Use of novel lab assays to examine the effect of pyrethroid-treated bed nets on blood-feeding success and longevity of highly insecticide-resistant Anopheles gambiae s.l. mosquitoes. Parasit Vectors 2022; 15:111. [PMID: 35346334 PMCID: PMC8962112 DOI: 10.1186/s13071-022-05220-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2021] [Accepted: 02/24/2022] [Indexed: 11/28/2022] Open
Abstract
Background There is a pressing need to improve understanding of how insecticide resistance affects the functional performance of insecticide-treated nets (ITNs). Standard WHO insecticide resistance monitoring assays are designed for resistance surveillance and do not necessarily provide insight into how different frequencies, mechanisms or intensities of resistance affect the ability of ITNs to reduce malaria transmission. Methods The current study presents some novel laboratory-based assays that attempt to better simulate realistic exposure of mosquitoes to ITNs and to quantify impact of exposure not only on instantaneous mortality, but also on blood-feeding and longevity, two traits that are central to transmission. The assays evaluated the performance of a standard ITN (Permanet® 2.0; Vestergaard Frandsen), a ‘next generation’ combination ITN with a resistance-breaking synergist (Permanet® 3.0) and an untreated net (UTN), against field-derived Anopheles gambiae sensu lato mosquitoes from Côte d’Ivoire exhibiting a 1500-fold increase in pyrethroid resistance relative to a standard susceptible strain. Results The study revealed that the standard ITN induced negligible instantaneous mortality against the resistant mosquitoes, whereas the resistance-breaking net caused high mortality and a reduction in blood-feeding. However, both ITNs still impacted long-term survival relative to the UTN. The impact on longevity depended on feeding status, with blood-fed mosquitoes living longer than unfed mosquitoes following ITN exposure. Exposure to both ITNs also reduced the blood-feeding success, the time spent on the net and blood-feeding duration, relative to the untreated net. Conclusion Although a standard ITN did not have as substantial instantaneous impact as the resistance-breaking net, it still had significant impacts on traits important for transmission. These results highlight the benefit of improved bioefficacy assays that allow for realistic exposure and consider sub- or pre-lethal effects to help assess the functional significance of insecticide resistance. Graphical Abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s13071-022-05220-y.
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Affiliation(s)
- Priscille Barreaux
- Liverpool School of Tropical Medicine, Liverpool, UK. .,Pennsylvania State University, State College, PA, USA. .,University of Neuchâtel, Neuchâtel, Switzerland.
| | | | - Raphael N'Guessan
- London School of Tropical Medicine, London, UK.,Vector Control Product Evaluation Centre, Institute Pierre Richet, Bouaké, Côte d'Ivoire
| | - Matthew B Thomas
- Pennsylvania State University, State College, PA, USA.,University of York, York, UK
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3
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Nash RK, Lambert B, NʼGuessan R, Ngufor C, Rowland M, Oxborough R, Moore S, Tungu P, Sherrard-Smith E, Churcher TS. Systematic review of the entomological impact of insecticide-treated nets evaluated using experimental hut trials in Africa. CURRENT RESEARCH IN PARASITOLOGY & VECTOR-BORNE DISEASES 2021; 1:100047. [PMID: 35284856 PMCID: PMC8906077 DOI: 10.1016/j.crpvbd.2021.100047] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 08/06/2021] [Accepted: 08/12/2021] [Indexed: 10/27/2022]
Abstract
Resistance of anopheline mosquitoes to pyrethroid insecticides is spreading rapidly across sub-Saharan Africa, diminishing the efficacy of insecticide-treated nets (ITNs) - the primary tool for preventing malaria. The entomological efficacy of indoor vector control interventions can be measured in experimental hut trials (EHTs), where hut structures resemble local housing, but allow the collection of mosquitoes that entered, exited, blood-fed and/or died. There is a need to understand how the spread of resistance changes ITN efficacy and to elucidate factors influencing EHT results, including differences in experimental hut design, to support the development of novel vector control tools. A comprehensive database of EHTs was compiled following a systematic review to identify all known trials investigating ITNs or indoor residual spraying across sub-Saharan Africa. This analysis focuses on EHTs investigating ITNs and uses Bayesian statistical models to characterise the complex interaction between ITNs and mosquitoes, the between-study variability, and the impact of pyrethroid resistance. As resistance rises, the entomological efficacy of ITNs declines. They induce less mortality and are less likely to deter mosquitoes from entering huts. Despite this, ITNs continue to offer considerable personal protection by reducing mosquito feeding until resistance reaches high levels. There are clear associations between the different entomological impacts of ITNs, though there is still substantial variability between studies, some of which can be accounted for by hut design. The relationship between EHT outcomes and the level of resistance (as measured by discriminating dose bioassays) is highly uncertain. The meta-analyses show that EHTs are an important reproducible assay for capturing the complex entomological efficacy of ITNs on blood-feeding mosquitoes. The impact of pyrethroid resistance on these measures appears broadly consistent across a wide geographical area once hut design is accounted for, suggesting results can be extrapolated beyond the sites where the trials were conducted. Further work is needed to understand factors influencing EHT outcomes and how the relationship between outcomes and resistance varies when different methods are used to assess the level of resistance in wild mosquito populations. This will allow more precise estimates of the efficacy of these important vector control tools.
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Affiliation(s)
- Rebecca K. Nash
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, Norfolk Place, London, W2 1PG, UK,Corresponding author.
| | - Ben Lambert
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, Norfolk Place, London, W2 1PG, UK
| | - Raphael NʼGuessan
- Institut Pierre Richet, Institut National de Santé Publique, Bouaké, Côte d’Ivoire,London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
| | - Corine Ngufor
- London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK,Centre de Recherches Entomologiques de Cotonou, Cotonou, Benin
| | - Mark Rowland
- London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
| | - Richard Oxborough
- PMI VectorLink Project, Abt Associates, 6130 Executive Blvd, Rockville, MD, 20852, USA
| | - Sarah Moore
- Vector Control Product Testing Unit, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Pwani, Tanzania,Swiss Tropical & Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland,University of Basel, Petersplatz 1, 4001, Basel, Switzerland,Nelson Mandela African Institute of Science and Technology (NM-AIST), P.O. Box 447, Tengeru, Tanzania
| | - Patrick Tungu
- National Institute for Medical Research (NIMR), P.O. Box 9653, Dar Es Salaam, Tanzania
| | - Ellie Sherrard-Smith
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, Norfolk Place, London, W2 1PG, UK
| | - Thomas S. Churcher
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, Norfolk Place, London, W2 1PG, UK
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4
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Namias A, Jobe NB, Paaijmans KP, Huijben S. The need for practical insecticide-resistance guidelines to effectively inform mosquito-borne disease control programs. eLife 2021; 10:e65655. [PMID: 34355693 PMCID: PMC8346280 DOI: 10.7554/elife.65655] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 07/26/2021] [Indexed: 11/13/2022] Open
Abstract
Monitoring local mosquito populations for insecticide resistance is critical for effective vector-borne disease control. However, widely used phenotypic assays, which are designed to monitor the emergence and spread of insecticide resistance (technical resistance), do not translate well to the efficacy of vector control products to suppress mosquito numbers in the field (practical resistance). This is because standard testing conditions such as environmental conditions, exposure dose, and type of substrate differ dramatically from those experienced by mosquitoes under field conditions. In addition, field mosquitoes have considerably different physiological characteristics such as age and blood-feeding status. Beyond this, indirect impacts of insecticide resistance and/or exposure on mosquito longevity, pathogen development, host-seeking behavior, and blood-feeding success impact disease transmission. Given the limited number of active ingredients currently available and the observed discordance between resistance and disease transmission, we conclude that additional testing guidelines are needed to determine practical resistance-the efficacy of vector control tools under relevant local conditions- in order to obtain programmatic impact.
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Affiliation(s)
- Alice Namias
- Département de Biologie, Ecole Normale Supérieure, PSL Research University, Paris, France
- Institut des Sciences de l'Evolution de Montpellier (ISEM), Université de Montpellier, CNRS, IRD, EPHE, Montpellier, France
| | - Ndey Bassin Jobe
- Center for Evolution and Medicine, School of Life Sciences, Arizona State University, Life Sciences C, Tempe, United States
| | - Krijn Petrus Paaijmans
- Center for Evolution and Medicine, School of Life Sciences, Arizona State University, Life Sciences C, Tempe, United States
- The Biodesign Center for Immunotherapy, Vaccines and Virotherapy, Arizona State University, Biodesign Institute, Tempe, United States
- ISGlobal, Carrer del Rosselló, Barcelona, Spain
- Centro de Investigação em Saúde de Manhiça (CISM), Distrito da Manhiça, Mozambique
| | - Silvie Huijben
- Center for Evolution and Medicine, School of Life Sciences, Arizona State University, Life Sciences C, Tempe, United States
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5
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Ingham VA, Brown F, Ranson H. Transcriptomic analysis reveals pronounced changes in gene expression due to sub-lethal pyrethroid exposure and ageing in insecticide resistance Anopheles coluzzii. BMC Genomics 2021; 22:337. [PMID: 33971808 PMCID: PMC8111724 DOI: 10.1186/s12864-021-07646-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Accepted: 04/23/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Malaria control is heavily reliant on the use of insecticides that target and kill the adult female Anopheline vector. The intensive use of insecticides of the pyrethroid class has led to widespread resistance in mosquito populations. The intensity of pyrethroid resistance in some settings in Africa means mosquitoes can contact bednets treated with this insecticide class multiple times with minimal mortality effects. Furthermore, both ageing and diel cycle have been shown to have large impacts on the resistance phenotype. Together, these traits may affect other aspects of vector biology controlling the vectorial capacity or fitness of the mosquito. RESULTS Here we show that sublethal exposure of a highly resistant Anopheles coluzzii population originally from Burkina Faso to the pyrethroid deltamethrin results in large and sustained changes to transcript expression. We identify five clear patterns in the data showing changes to transcripts relating to: DNA repair, respiration, translation, behaviour and oxioreductase processes. Further, we highlight differential regulation of transcripts from detoxification families previously linked with insecticide resistance, in addition to clear down-regulation of the oxidative phosphorylation pathway both indicative of changes in metabolism post-exposure. Finally, we show that both ageing and diel cycle have major effects on known insecticide resistance related transcripts. CONCLUSION Sub-lethal pyrethroid exposure, ageing and the diel cycle results in large-scale changes in the transcriptome of the major malaria vector Anopheles coluzzii. Our data strongly supports further phenotypic studies on how transcriptional changes such as reduced expression of the oxidative phosphorylation pathway or pyrethroid induced changes to redox state might impact key mosquito traits, such as vectorial capacity and life history traits.
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Affiliation(s)
- V A Ingham
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, L35QA, UK. .,Present Address: Parasitology Unit, Centre for Infectious Diseases, Universitätsklinikum, Im Neuenheimer Feld 324, 69120, Heidelberg, Germany.
| | - F Brown
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, L35QA, UK.,Department of Epidemiology and Population Health, Institute of Infection and Global Health, Faculty of Health and Life Sciences, Leahurst Campus, University of Liverpool, Neston, CH647TE, UK
| | - H Ranson
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, L35QA, UK
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6
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Nouage L, Elanga-Ndille E, Binyang A, Tchouakui M, Atsatse T, Ndo C, Kekeunou S, Wondji CS. Influence of GST- and P450-based metabolic resistance to pyrethroids on blood feeding in the major African malaria vector Anopheles funestus. PLoS One 2020; 15:e0230984. [PMID: 32946446 PMCID: PMC7500606 DOI: 10.1371/journal.pone.0230984] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Accepted: 08/26/2020] [Indexed: 11/19/2022] Open
Abstract
Insecticide resistance genes are often associated with pleiotropic effects on various mosquito life-history traits. However, very little information is available on the impact of insecticide resistance on blood feeding process in mosquitoes. Here, using two recently detected DNA-based metabolic markers in the major malaria vector, An. funestus, we investigated how metabolic resistance genes could affect the blood meal intake. After allowing both the field F1 and lab F8 Anopheles funestus strains to feed on the human arm for 30 minutes, we assessed the association between key parameters of blood meal process including, probing time, feeding duration, blood feeding success, blood meal size, and markers of glutathione S-transferase (L119F-GSTe2) and cytochrome P450 (CYP6P9a_R)-mediated metabolic resistance. None of the parameters of blood meal process was associated with L119F-GSTe2 genotypes. By contrast, for CYP6P9a_R, homozygous resistant mosquitoes were significantly more able to blood-feed than homozygous susceptible (OR = 3.3; CI 95%: 1.4-7.7; P = 0.01) mosquitoes. Moreover, the volume of blood meal ingested by CYP6P9a-SS mosquitoes was lower than that of CYP6P9a-RS (P<0.004) and of CYP6P9a-RR (P<0.006). This suggests that CYP6P9a gene is inked with the feeding success and blood meal size of An. funestus. However, no correlation was found in the expression of CYP6P9a and that of genes encoding for salivary proteins involved in blood meal process. This study suggests that P450-based metabolic resistance may influence the blood feeding process of Anopheles funestus mosquito and consequently its ability to transmit malaria parasites.
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Affiliation(s)
- Lynda Nouage
- Department of Medical Entomology, Centre for Research in Infectious Diseases (CRID), Yaoundé, Cameroon
- Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, Yaoundé, Cameroon
| | - Emmanuel Elanga-Ndille
- Department of Medical Entomology, Centre for Research in Infectious Diseases (CRID), Yaoundé, Cameroon
| | - Achille Binyang
- Department of Medical Entomology, Centre for Research in Infectious Diseases (CRID), Yaoundé, Cameroon
- Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, Yaoundé, Cameroon
| | - Magellan Tchouakui
- Department of Medical Entomology, Centre for Research in Infectious Diseases (CRID), Yaoundé, Cameroon
- Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, Yaoundé, Cameroon
| | - Tatiane Atsatse
- Department of Medical Entomology, Centre for Research in Infectious Diseases (CRID), Yaoundé, Cameroon
- Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, Yaoundé, Cameroon
| | - Cyrille Ndo
- Department of Parasitology and Microbiology, Centre for Research in Infectious Diseases (CRID), Yaoundé, Cameroon
- Department of Biological Sciences, Faculty of Medicine and Pharmaceutical Sciences, University of Douala, Douala, Cameroon
| | - Sévilor Kekeunou
- Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, Yaoundé, Cameroon
| | - Charles S. Wondji
- Department of Medical Entomology, Centre for Research in Infectious Diseases (CRID), Yaoundé, Cameroon
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
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7
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Hughes A, Foster GM, Guy A, Matope A, Abe M, Towers D, McCall PJ. Quantifying late-stage host-seeking behaviour of Anopheles gambiae at the insecticidal net interface using a baited-box bioassay. Malar J 2020; 19:140. [PMID: 32264900 PMCID: PMC7140563 DOI: 10.1186/s12936-020-03213-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2020] [Accepted: 03/28/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Insecticide-treated nets (ITNs) are losing efficacy against pyrethroid-resistant malaria vector populations throughout Africa. Safeguarding bed net efficacy, vital for effective malaria control, requires greater knowledge of mosquito-ITN interactions and how this impacts on the mosquito. METHODS A purpose-built benchtop apparatus with a closed 10 cm cubic chamber (the 'Baited-box') was used to video record behaviour of individual free-flying female Anopheles gambiae during approach and blood-feeding on a human hand through untreated nets and ITNs at close range. Time and duration of defined behavioural events, and knockdown and mortality at 1- and 24-h post-exposure respectively, were recorded for pyrethroid susceptible and resistant mosquitoes. RESULTS Using three human volunteers differing in relative attractiveness to mosquitoes, 328 mosquitoes were individually tested. There were no significant differences between response rates to ITNs and untreated nets (P > 0.1) or between resistant (Tiassalé) and susceptible (Kisumu) mosquito strains, at untreated nets (P = 0.39) or PermaNet 2.0 (P = 1). The sequence of behavioural events from host-seeking to completion of blood-feeding was consistent in all tests but duration and start time of events involving net contact were reduced or delayed respectively with ITNs. Blood-feeding durations at untreated nets (means from 4.25 to 8.47 min (95% confidence interval (CI) = 3.39-9.89) at 3 human volunteers) were reduced by 37-50% at PermaNet 2.0, in susceptible (mean 2.59-4.72 min, 95% CI = 1.54-5.5, P = < 0.05) and resistant (mean 4.20 min, 95% CI = 3.42-4.97, P = 0.01) strains. Total accumulated net contact was approximately 50% lower at PermaNet and Olyset ITNs (P < 0.0001) in susceptible (two of the three volunteers) and resistant mosquitoes. Times prior to first net contact were similar at untreated nets and ITNs (P > 0.2), and neither ITN type showed detectable spatial repellency. After initial contact, blood-feeding commenced later at Olyset (mean 2.76 min, 95% CI = 1.74-3.76, P = 0.0009) and PermaNet (mean 2.4 min, 95% CI = 1.52-3.33, P = 0.0058) than untreated netting (mean 0.68 min, 95% CI = 0.42-0.94). CONCLUSIONS The baited box offers a simple method for detailed characterization of mosquito behavioural responses to insecticidal nets, for comparing entomological modes of action between nets and for defining the behavioural responses of particular mosquito strains or populations. The device has potential as a screening assay in the search for novel net treatments and for investigations into behavioural resistance mechanisms.
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Affiliation(s)
- Angela Hughes
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Geraldine M Foster
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Amy Guy
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Agnes Matope
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Mayumi Abe
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - David Towers
- Optical Engineering Group, School of Engineering, University of Warwick, Coventry, CV4 7AL, UK
| | - Philip J McCall
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
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8
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Hauser G, Thiévent K, Koella JC. Consequences of larval competition and exposure to permethrin for the development of the rodent malaria Plasmodium berghei in the mosquito Anopheles gambiae. Parasit Vectors 2020; 13:107. [PMID: 32106886 PMCID: PMC7045583 DOI: 10.1186/s13071-020-3983-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Accepted: 02/18/2020] [Indexed: 01/16/2023] Open
Abstract
Background Mosquitoes and other vectors are often exposed to sublethal doses of insecticides. Larvae can be exposed to the run-off of agricultural use, and adults can be irritated by insecticides used against them and move away before they have picked up a lethal dose. This sublethal exposure may affect the success of control of insect-borne diseases, for it may affect the competence of insects to transmit parasites, in particular if the insects are undernourished. Methods We assessed how exposure of larvae and adults to a sublethal dose of permethrin (a pyrethroid) and how larval competition for food affect several aspects of the vector competence of the mosquito Anopheles gambiae for the malaria parasite Plasmodium berghei. We infected mosquitoes with P. berghei and measured the longevity and the prevalence and intensity of infection to test for an effect of our treatments. Results Our general result was that the exposure to the insecticide helped mosquitoes deal with infection by malaria. Exposure of either larvae or adults decreased the likelihood that mosquitoes were infected by about 20%, but did not effect the parasite load. Exposure also increased the lifespan of infected mosquitoes, but only if they had been reared in competition. Larval competition had no effect on the prevalence of infection, but increased parasite load. These effects may be a consequence of the machinery governing oxidative stress, which underlies the responses of mosquitoes to insecticides, to food stress and to parasites. Conclusions We conclude that insecticide residues are likely to affect the ability of mosquitoes to carry and transmit pathogens such as malaria, irrespective of the stage at which they are exposed to the insecticide. Our results stress the need for further studies to consider sublethal doses in the context of vector ecology and vector-borne disease epidemiology.![]()
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Affiliation(s)
- Gaël Hauser
- Institute of Biology, University of Neuchâtel, Rue Emile-Argand 11, 2000, Neuchâtel, Switzerland.
| | - Kevin Thiévent
- Institute of Biology, University of Neuchâtel, Rue Emile-Argand 11, 2000, Neuchâtel, Switzerland
| | - Jacob C Koella
- Institute of Biology, University of Neuchâtel, Rue Emile-Argand 11, 2000, Neuchâtel, Switzerland
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9
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Lajeunesse MJ, Avello DA, Behrmann MS, Buschbacher TJ, Carey K, Carroll J, Chafin TJ, Elkott F, Faust AM, Fauver H, Figueroa GD, Flaig LL, Gauta SA, Gonzalez C, Graham RM, Hamdan K, Hanlon T, Hashami SN, Huynh D, Knaffl JL, Lanzas M, Libell NM, McCabe C, Metzger J, Mitchell I, Morales MA, Nayyar YR, Perkins A, Phan TA, Pidgeon NT, Ritter CL, Rosales VC, Santiago O, Stephens R, Taylor EJ, Thomas AJ, Yanez NE. Infected Mosquitoes Have Altered Behavior to Repellents: A Systematic Review and Meta-analysis. JOURNAL OF MEDICAL ENTOMOLOGY 2020; 57:542-550. [PMID: 31755530 DOI: 10.1093/jme/tjz209] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Indexed: 06/10/2023]
Abstract
Here we conducted a systematic review and meta-analysis to reach a consensus on whether infected and uninfected mosquitoes respond differently to repellents. After screening 2,316 published studies, theses, and conference abstracts, we identified 18 studies that tested whether infection status modulated the effectiveness of repellents. Thirteen of these studies had outcomes available for meta-analysis, and overall, seven repellents were tested (typically DEET with 62% of outcomes), six mosquito species had repellence behaviors measured (typically Aedes aegypti (L.) (Diptera: Culicidae) mosquitoes with 71% of outcomes), and a broad diversity of infections were tested including Sindbis virus (Togaviridae: Alphavirus) (33% of outcomes), Dengue (Flaviviridae: Flavivirus) (31%), malaria (Plasmodium berghei Vincke & Lips (Haemospororida: Plasmodiidae) or P. falciparum Welch (Haemospororida: Plasmodiidae); 25%), Zika (Flaviviridae: Flavivirus) (7%), and microsporidia (4%). Pooling all outcomes with meta-analysis, we found that repellents were less effective against infected mosquitoes-marking an average 62% reduction in protective efficacy relative to uninfected mosquitoes (pooled odds ratio = 0.38, 95% confidence interval = 0.22-0.66; k = 96). Older infected mosquitoes were also more likely to show altered responses and loss of sensitivity to repellents, emphasizing the challenge of distinguishing between age or incubation period effects. Plasmodium- or Dengue-infected mosquitoes also did not show altered responses to repellents; however, Dengue-mosquito systems used inoculation practices that can introduce variability in repellency responses. Given our findings that repellents offer less protection against infected mosquitoes and that these vectors are the most dangerous in terms of disease transmission, then trials on repellent effectiveness should incorporate infected mosquitoes to improve predictability in blocking vector-human contact.
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Affiliation(s)
- Marc J Lajeunesse
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Daniel A Avello
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Morgan S Behrmann
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | | | - Kayla Carey
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Jordyn Carroll
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Timothy J Chafin
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Fatima Elkott
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Ami M Faust
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Hope Fauver
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | | | - Louisa L Flaig
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Sarah A Gauta
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Cristian Gonzalez
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Rowan M Graham
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Khalid Hamdan
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Thomas Hanlon
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Syad N Hashami
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Dora Huynh
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Jessica L Knaffl
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Milton Lanzas
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Nicole M Libell
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Casey McCabe
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Jamie Metzger
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Isabella Mitchell
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Marisol A Morales
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Yogi R Nayyar
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Aaron Perkins
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Tam-Anh Phan
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Nicholas T Pidgeon
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Camryn L Ritter
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Veronica C Rosales
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Olivia Santiago
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Rebecca Stephens
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Ethan J Taylor
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Anup J Thomas
- Department of Integrative Biology, University of South Florida, Tampa, FL
| | - Nicholas E Yanez
- Department of Integrative Biology, University of South Florida, Tampa, FL
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