1
|
Andrianinarivomanana TM, Randrianaivo FT, Andriamiarimanana MR, Razafimamonjy MR, Velonirina HJ, Puchot N, Girod R, Bourgouin C. Colonization of Anopheles coustani, a neglected malaria vector in Madagascar. Parasite 2024; 31:31. [PMID: 38896103 PMCID: PMC11186460 DOI: 10.1051/parasite/2024032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2024] [Accepted: 05/24/2024] [Indexed: 06/21/2024] Open
Abstract
Anopheles coustani has long been recognized as a secondary malaria vector in Africa. It has recently been involved in the transmission of both Plasmodium falciparum and P. vivax in Madagascar. As most secondary malaria vectors, An. coustani mainly bites outdoors, which renders the control of this mosquito species difficult using classical malaria control measures, such as the use of bed nets or indoor residual spraying of insecticides. For a better understanding of the biology and vector competence of a vector species, it is useful to rear the species in the laboratory. The absence of a colony hinders the assessment of the bionomics of a species and the development of adapted control strategies. Here, we report the first successful establishment of an An. coustani colony from mosquitoes collected in Madagascar. We used a forced copulation procedure as this mosquito species will not mate in cages. We describe our mosquito colonization procedure with detailed biological features concerning larval to adult development and survival, recorded over the first six critical generations. The procedure should be easily applicable to An. coustani from different African countries, facilitating local investigation of An. coustani vector competence and insecticide resistance using the colony as a reference.
Collapse
Affiliation(s)
| | | | | | | | | | - Nicolas Puchot
- Institut Pasteur, Université de Paris Cité, Biology of Host-Parasite Interactions Paris France
| | - Romain Girod
- Institut Pasteur de Madagascar, Medical Entomology Unit Antananarivo Madagascar
| | - Catherine Bourgouin
- Institut Pasteur, Université de Paris Cité, Biology of Host-Parasite Interactions Paris France
| |
Collapse
|
2
|
Puchot N, Lecoq MT, Carinci R, Duchemin JB, Gendrin M, Bourgouin C. Establishment of a colony of Anopheles darlingi from French Guiana for vector competence studies on malaria transmission. FRONTIERS IN TROPICAL DISEASES 2022. [DOI: 10.3389/fitd.2022.949300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Anopheles darlingi is a major vector of both Plasmodium falciparum and Plasmodium vivax in South and Central America including French Guiana. However, the vector competence and physiology of this mosquito species have been scarcely studied due to difficulties in rearing it in the laboratory. Here, we report the successful establishment of a robust colony, from a mosquito collection in French Guiana. We describe our mosquito colonization procedure with relevant information on environmental conditions, mating ability, larval development, and survival, recorded over the first six critical generations. Experimental infection showed that our An. darlingi colony has a moderate permissiveness to in vitro produced gametocytes of the P. falciparum NF54 strain originating from Africa. This colony, which has reached its 21st generation, will allow further characterization of An. darlingi life-history traits and of Plasmodium–mosquito interactions with South American malaria parasites.
Collapse
|
3
|
Abstract
Gene drives are selfish genetic elements that are transmitted to progeny at super-Mendelian (>50%) frequencies. Recently developed CRISPR-Cas9-based gene-drive systems are highly efficient in laboratory settings, offering the potential to reduce the prevalence of vector-borne diseases, crop pests and non-native invasive species. However, concerns have been raised regarding the potential unintended impacts of gene-drive systems. This Review summarizes the phenomenal progress in this field, focusing on optimal design features for full-drive elements (drives with linked Cas9 and guide RNA components) that either suppress target mosquito populations or modify them to prevent pathogen transmission, allelic drives for updating genetic elements, mitigating strategies including trans-complementing split-drives and genetic neutralizing elements, and the adaptation of drive technology to other organisms. These scientific advances, combined with ethical and social considerations, will facilitate the transparent and responsible advancement of these technologies towards field implementation.
Collapse
Affiliation(s)
- Ethan Bier
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, USA.
| |
Collapse
|
4
|
Panthawong A, Sukkanon C, Ngoen-Klan R, Hii J, Chareonviriyaphap T. Forced Egg Laying Method to Establish F1 Progeny from Field Populations and Laboratory Strains of Anopheles Mosquitoes (Diptera: Culicidae) in Thailand. JOURNAL OF MEDICAL ENTOMOLOGY 2021; 58:2107-2113. [PMID: 34104962 DOI: 10.1093/jme/tjab105] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Indexed: 06/12/2023]
Abstract
Successful monitoring of physiological resistance of malaria vectors requires about 150 female mosquitoes for a single set of tests. In some situations, the sampling effort is insufficient due to the low number of field-caught mosquitoes. To address this challenge, we demonstrate the feasibility of using the forced oviposition method for producing F1 from field-caught Anopheles mosquitoes. A total of 430 and 598 gravid Anopheles females from four laboratory strains and five field populations, respectively, were tested. After blood feeding, gravid mosquitoes were individually introduced into transparent plastic vials, containing moistened cotton balls topped with a 4 cm2 piece of filter paper. The number of eggs, hatching larvae, pupation, and adult emergence were recorded daily. The mean number of eggs per female mosquito ranged from 39.3 for Anopheles cracens to 93.6 for Anopheles dirus in the laboratory strains, and from 36.3 for Anopheles harrisoni to 147.6 for Anopheles barbirostris s.l. in the field populations. A relatively high egg hatching rate was found in An. dirus (95.85%), Anopheles minimus (78.22%), and An. cracens (75.59%). Similarly, a relatively high pupation rate was found for almost all test species ranging from 66% for An. minimus to 98.7% for Anopheles maculatus, and lowest for An. harrisoni (43.9%). Highly successful adult emergence rate was observed among 85-100% of pupae that emerged in all tested mosquito populations. The in-tube forced oviposition method is a promising method for the production of sufficient F1 progeny for molecular identification, vector competence, insecticide resistance, and bioassay studies.
Collapse
Affiliation(s)
- Amonrat Panthawong
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand
| | - Chutipong Sukkanon
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand
- Department of Medical Technology, School of Allied Health Sciences, Walailak University, Nakhon Si Thammarat 80161, Thailand
| | - Ratchadawan Ngoen-Klan
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand
| | - Jeffrey Hii
- Malaria Consortium Asia Regional Office, Faculty of Tropical Medicine, Mahidol University, Bangkok 10400, Thailand
- College of Public Health, Medical and Veterinary Sciences, James Cook University, North Queensland, QLD 4810, Australia
| | | |
Collapse
|
5
|
Nambunga IH, Msugupakulya BJ, Hape EE, Mshani IH, Kahamba NF, Mkandawile G, Mabula DM, Njalambaha RM, Kaindoa EW, Muyaga LL, Hermy MRG, Tripet F, Ferguson HM, Ngowo HS, Okumu FO. Wild populations of malaria vectors can mate both inside and outside human dwellings. Parasit Vectors 2021; 14:514. [PMID: 34620227 PMCID: PMC8499572 DOI: 10.1186/s13071-021-04989-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 09/01/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Wild populations of Anopheles mosquitoes are generally thought to mate outdoors in swarms, although once colonized, they also mate readily inside laboratory cages. This study investigated whether the malaria vectors Anopheles funestus and Anopheles arabiensis can also naturally mate inside human dwellings. METHOD Mosquitoes were sampled from three volunteer-occupied experimental huts in a rural Tanzanian village at 6:00 p.m. each evening, after which the huts were completely sealed and sampling was repeated at 11:00 p.m and 6 a.m. the next morning to compare the proportions of inseminated females. Similarly timed collections were done inside local unsealed village houses. Lastly, wild-caught larvae and pupae were introduced inside or outside experimental huts constructed inside two semi-field screened chambers. The huts were then sealed and fitted with exit traps, allowing mosquito egress but not entry. Mating was assessed in subsequent days by sampling and dissecting emergent adults caught indoors, outdoors and in exit traps. RESULTS Proportions of inseminated females inside the experimental huts in the village increased from approximately 60% at 6 p.m. to approximately 90% the following morning despite no new mosquitoes entering the huts after 6 p.m. Insemination in the local homes increased from approximately 78% to approximately 93% over the same time points. In the semi-field observations of wild-caught captive mosquitoes, the proportions of inseminated An. funestus were 20.9% (95% confidence interval [CI]: ± 2.8) outdoors, 25.2% (95% CI: ± 3.4) indoors and 16.8% (± 8.3) in exit traps, while the proportions of inseminated An. arabiensis were 42.3% (95% CI: ± 5.5) outdoors, 47.4% (95% CI: ± 4.7) indoors and 37.1% (CI: ± 6.8) in exit traps. CONCLUSION Wild populations of An. funestus and An. arabiensis in these study villages can mate both inside and outside human dwellings. Most of the mating clearly happens before the mosquitoes enter houses, but additional mating happens indoors. The ecological significance of such indoor mating remains to be determined. The observed insemination inside the experimental huts fitted with exit traps and in the unsealed village houses suggests that the indoor mating happens voluntarily even under unrestricted egress. These findings may inspire improved vector control, such as by targeting males indoors, and potentially inform alternative methods for colonizing strongly eurygamic Anopheles species (e.g. An. funestus) inside laboratories or semi-field chambers.
Collapse
Affiliation(s)
- Ismail H. Nambunga
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK
| | - Betwel J. Msugupakulya
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
- School of Life Science and Bioengineering, The Nelson Mandela African Institution of Sciences & Technology, Arusha, Tanzania
| | - Emmanuel E. Hape
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK
| | - Issa H. Mshani
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK
| | - Najat F. Kahamba
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK
- School of Life Science and Bioengineering, The Nelson Mandela African Institution of Sciences & Technology, Arusha, Tanzania
| | - Gustav Mkandawile
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Daniel M. Mabula
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Rukiyah M. Njalambaha
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Emmanuel W. Kaindoa
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
- School of Life Science and Bioengineering, The Nelson Mandela African Institution of Sciences & Technology, Arusha, Tanzania
- School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Park Town, Republic of South Africa
| | - Letus L. Muyaga
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Marie R. G. Hermy
- Disease Vector Group, Chemical Ecology, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Alnarp, Sweden
| | - Frederic Tripet
- Centre for Applied Entomology and Parasitology, School of Life Sciences, Keele University, Newcastle-under-Lyme, UK
| | - Heather M. Ferguson
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK
| | - Halfan S. Ngowo
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK
| | - Fredros O. Okumu
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK
- School of Life Science and Bioengineering, The Nelson Mandela African Institution of Sciences & Technology, Arusha, Tanzania
- School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Park Town, Republic of South Africa
| |
Collapse
|
6
|
Ngowo HS, Hape EE, Matthiopoulos J, Ferguson HM, Okumu FO. Fitness characteristics of the malaria vector Anopheles funestus during an attempted laboratory colonization. Malar J 2021; 20:148. [PMID: 33712003 PMCID: PMC7955623 DOI: 10.1186/s12936-021-03677-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Accepted: 03/01/2021] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND The malaria vector Anopheles funestus is increasingly recognized as a dominant vector of residual transmission in many African settings. Efforts to better understand its biology and control are significantly impeded by the difficulties of colonizing it under laboratory conditions. To identify key bottlenecks in colonization, this study compared the development and fitness characteristics of wild An. funestus from Tanzania (FUTAZ) and their F1 offspring during colonization attempts. The demography and reproductive success of wild FUTAZ offspring were compared to that of individuals from one of the only An. funestus strains that has been successfully colonized (FUMOZ, from Mozambique) under similar laboratory conditions. METHODS Wild An. funestus (FUTAZ) were collected from three Tanzanian villages and maintained inside an insectary at 70-85% RH, 25-27 °C and 12 h:12 h photoperiod. Eggs from these females were used to establish three replicate F1 laboratory generations. Larval development, survival, fecundity, mating success, percentage pupation and wing length were measured in the F1 -FUTAZ offspring and compared with wild FUTAZ and FUMOZ mosquitoes. RESULTS Wild FUTAZ laid fewer eggs (64.1; 95% CI [63.2, 65.0]) than FUMOZ females (76.1; 95% CI [73.3, 79.1]). Survival of F1-FUTAZ larvae under laboratory conditions was low, with an egg-to-pupae conversion rate of only 5.9% compared to 27.4% in FUMOZ. The median lifespan of F1-FUTAZ females (32 days) and males (33 days) was lower than FUMOZ (52 and 49 for females and males respectively). The proportion of female F1-FUTAZ inseminated under laboratory conditions (9%) was considerably lower than either FUMOZ (72%) or wild-caught FUTAZ females (92%). This resulted in nearly zero viable F2-FUTAZ eggs produced. Wild FUTAZ wings appear to be larger compared to the lab reared F1-FUTAZ and FUMOZ. CONCLUSIONS This study indicates that poor larval survival, mating success, low fecundity and shorter survival under laboratory conditions all contribute to difficulties in colonizing of An. funestus. Future studies should focus on enhancing these aspects of An. funestus fitness in the laboratory, with the biggest barrier likely to be poor mating.
Collapse
Affiliation(s)
- Halfan S Ngowo
- Department of Environmental Health and Ecological Sciences, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania. .,Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, G12, 8QQ, UK.
| | - Emmanuel E Hape
- Department of Environmental Health and Ecological Sciences, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania.,Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, G12, 8QQ, UK
| | - Jason Matthiopoulos
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, G12, 8QQ, UK
| | - Heather M Ferguson
- Department of Environmental Health and Ecological Sciences, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania.,Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, G12, 8QQ, UK
| | - Fredros O Okumu
- Department of Environmental Health and Ecological Sciences, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania.,Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, G12, 8QQ, UK.,School of Public Health, University of the Witwatersrand, 1 Smuts Avenue, Braamfontein, 2000, Republic of South Africa.,School of Life Science and Bioengineering, Nelson Mandela African Institution of Science and Technology, P.O. Box 447, Arusha, Tanzania
| |
Collapse
|
7
|
Peirce MJ, Mitchell SN, Kakani EG, Scarpelli P, South A, Shaw WR, Werling KL, Gabrieli P, Marcenac P, Bordoni M, Talesa V, Catteruccia F. JNK signaling regulates oviposition in the malaria vector Anopheles gambiae. Sci Rep 2020; 10:14344. [PMID: 32873857 PMCID: PMC7462981 DOI: 10.1038/s41598-020-71291-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Accepted: 07/30/2020] [Indexed: 02/05/2023] Open
Abstract
The reproductive fitness of the Anopheles gambiae mosquito represents a promising target to prevent malaria transmission. The ecdysteroid hormone 20-hydroxyecdysone (20E), transferred from male to female during copulation, is key to An. gambiae reproductive success as it licenses females to oviposit eggs developed after blood feeding. Here we show that 20E-triggered oviposition in these mosquitoes is regulated by the stress- and immune-responsive c-Jun N-terminal kinase (JNK). The heads of mated females exhibit a transcriptional signature reminiscent of a JNK-dependent wounding response, while mating—or injection of virgins with exogenous 20E—selectively activates JNK in the same tissue. RNAi-mediated depletion of JNK pathway components inhibits oviposition in mated females, whereas JNK activation by silencing the JNK phosphatase puckered induces egg laying in virgins. Together, these data identify JNK as a potential conduit linking stress responses and reproductive success in the most important vector of malaria.
Collapse
Affiliation(s)
- Matthew J Peirce
- Dipartimento di Medicina Sperimentale, Università Degli Studi di Perugia, Sant' Andrea Delle Fratte, Piano 4, Edificio D, Piazzale Gambuli 1, 06132, Perugia, Italy.
| | - Sara N Mitchell
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, 665 Huntington Avenue, Building 1, Room 103, Boston, MA, 02115, USA.,Verily Life Sciences, South San Francisco, CA, 94080, USA
| | - Evdoxia G Kakani
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, 665 Huntington Avenue, Building 1, Room 103, Boston, MA, 02115, USA.,Verily Life Sciences, South San Francisco, CA, 94080, USA
| | - Paolo Scarpelli
- Dipartimento di Medicina Sperimentale, Università Degli Studi di Perugia, Sant' Andrea Delle Fratte, Piano 4, Edificio D, Piazzale Gambuli 1, 06132, Perugia, Italy
| | - Adam South
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, 665 Huntington Avenue, Building 1, Room 103, Boston, MA, 02115, USA
| | - W Robert Shaw
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, 665 Huntington Avenue, Building 1, Room 103, Boston, MA, 02115, USA
| | - Kristine L Werling
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, 665 Huntington Avenue, Building 1, Room 103, Boston, MA, 02115, USA
| | - Paolo Gabrieli
- Dipartimento di Medicina Sperimentale, Università Degli Studi di Perugia, Sant' Andrea Delle Fratte, Piano 4, Edificio D, Piazzale Gambuli 1, 06132, Perugia, Italy.,Dipartimento Bioscienze, University of Milan, 20133, Milan, Italy
| | - Perrine Marcenac
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, 665 Huntington Avenue, Building 1, Room 103, Boston, MA, 02115, USA
| | - Martina Bordoni
- Dipartimento di Medicina Sperimentale, Università Degli Studi di Perugia, Sant' Andrea Delle Fratte, Piano 4, Edificio D, Piazzale Gambuli 1, 06132, Perugia, Italy
| | - Vincenzo Talesa
- Dipartimento di Medicina Sperimentale, Università Degli Studi di Perugia, Sant' Andrea Delle Fratte, Piano 4, Edificio D, Piazzale Gambuli 1, 06132, Perugia, Italy
| | - Flaminia Catteruccia
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, 665 Huntington Avenue, Building 1, Room 103, Boston, MA, 02115, USA.
| |
Collapse
|
8
|
Evidence of Insecticide Resistance to Pyrethroids and Bendiocarb in Anopheles funestus from Tsararano, Marovoay District, Madagascar. BIOMED RESEARCH INTERNATIONAL 2018; 2018:5806179. [PMID: 30402485 PMCID: PMC6196927 DOI: 10.1155/2018/5806179] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Revised: 05/17/2018] [Accepted: 09/20/2018] [Indexed: 12/12/2022]
Abstract
Introduction In Madagascar, malaria control relies on the countrywide use of long lasting insecticide treated bed nets (LLINs) and on indoor residual spraying (IRS) in the central highland area as well as a small area on the eastern coast. We tested insecticide resistance mechanisms of Anopheles funestus from Tsararano, a malaria endemic village in the coastal health district of Marovoay. Methods Insecticide susceptibility bioassays were done in July 2017 on first-generation Anopheles funestus (F1) to assess (i) the susceptibility to permethrin (0.05%), deltamethrin (0.05%), DDT (4%), malathion (5%), fenitrothion (1%), and bendiocarb (0.1%); (ii) the effect of preexposure to the piperonyl butoxide (PBO) synergist; and (iii) the enzymatic activities of cytochrome P450, esterases, and glutathione S-transferases (GST). Results Our results demonstrated that An. funestus was phenotypically resistant to pyrethroids and bendiocarb, with a mortality rate (MR) of 33.6% (95%CI: 24.5-43.7%) and 86% (95%CI: 77.6-92.1%), respectively. In contrast, An. funestus were 100% susceptible to DDT and organophosphates (malathion and fenitrothion). Preexposure of An. funestus to PBO synergist significantly restored the susceptibility to bendiocarb (MR=100%) and increased the MR in the pyrethroid group, from 96% (95%CI: 90.0-98.9%) to 100% for deltamethrin and permethrin, respectively (χ2 = 43, df = 3, P< 0.0001). Enzymatic activities of cytochrome P450 and α-esterases were significantly elevated among An. funestus compared with the IPM reference strain (Mann-Whitney U= 30, P<0.0001; U = 145.5, P <0.0001, respectively). No significant differences of β-esterases activities compared to the IPM reference strain were observed (Mann-Whitney U = 392.5, P = 0.08). Conclusion In Tsararano, despite the absence of an IRS programme, there is evidence of high levels of insecticide resistance to pyrethroids and bendiocarb in An.
Collapse
|