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Genetic structure and resistance to pyrethroids in Aedes aegypti populations in French Guiana: Preliminary results and perspectives

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Abstract

Background: Aedes aegypti is vector of dengue and chikungunya viruses in French Guiana. A strong pyrethroid resistance has posed questions on the impact of vector control and resistance management. A prerequisite to improve those strategies is the investigation on population dynamics and factors which influence it. Therefore, we have implemented a population genetic study associated with deltamethrin resistance monitoring to provide further knowledge on these questions. Material and Methods: Two sites of 1 km² in Saint-Georges de l’Oyapock (SGO) and Cayenne (CAY) were prospected for mosquito immature stages in December 2013. F0 females were genotyped for 13 microsatellites and for the knockdown resistance associated mutation V1016I. Genetic diversity and differentiation indices were obtained in Arlequin software. Genetic structure among samples was tested in the program STRUCTURE. Evolutionary scenario probabilities and estimates were computed in DIY-ABC. Results: We detected the presence of two populations (k=2) congruent with each locality, with low but significant differentiation levels. Both populations exhibited similar effective population sizes and overall diversity. However, different evolutionary scenarios were obtained for each population. The V1016I kdr mutation is almost fixed in CAY population while SGO exhibited a larger proportion of heterozygotes. Conclusion: Genetic differentiation between the two populations suggests barriers to gene flow that may limit the exchange of resistance alleles. Therefore, the expansion of insecticide resistance in each population may also be due to local selective pressure. Additional spatial and temporal investigations are being conducted to confirm this hypothesis.Background: Aedes aegypti is vector of dengue and chikungunya viruses in French Guiana. A strong pyrethroid resistance has posed questions on the impact of vector control and resistance management. A prerequisite to improve those strategies is the investigation on population dynamics and factors which influence it. Therefore, we have implemented a population genetic study associated with deltamethrin resistance monitoring to provide further knowledge on these questions. Material and Methods: Two sites of 1 km² in Saint-Georges de l’Oyapock (SGO) and Cayenne (CAY) were prospected for mosquito immature stages in December 2013. F0 females were genotyped for 13 microsatellites and for the knockdown resistance associated mutation V1016I. Genetic diversity and differentiation indices were obtained in Arlequin software. Genetic structure among samples was tested in the program STRUCTURE. Evolutionary scenario probabilities and estimates were computed in DIY-ABC. Results: We detected the presence of two populations (k=2) congruent with each locality, with low but significant differentiation levels. Both populations exhibited similar effective population sizes and overall diversity. However, different evolutionary scenarios were obtained for each population. The V1016I kdr mutation is almost fixed in CAY population while SGO exhibited a larger proportion of heterozygotes. Conclusion: Genetic differentiation between the two populations suggests barriers to gene flow that may limit the exchange of resistance alleles. Therefore, the expansion of insecticide resistance in each population may also be due to local selective pressure. Additional spatial and temporal investigations are being conducted to confirm this hypothesis.
42
Amazonian Conference on Emerging and Infectious Diseases - Cayenne September 2014
,
Genetic structure and resistance to pyrethroids in Aedes aegypti populations
in French Guiana: Preliminary results and perspectives
P. Salgueiro1, A. Guidez2, P. Gaborit2, J. Issaly2, R. Girod2, J. Pinto1, I. Dusfour2
1
CMDT/IHMT, Lisbon, Portugal ;
2
Unité d'entomologie médicale, Institut Pasteur de la
Guyane, Cayenne, France
Background: Aedes aegypti is vector of dengue and chikungunya viruses in French Guiana. A
strong pyrethroid resistance has posed questions on the impact of vector control and resistance
management. A prerequisite to improve those strategies is the investigation on population dynamics
and factors which influence it. Therefore, we have implemented a population genetic study
associated with deltamethrin resistance monitoring to provide further knowledge on these questions.
Material and Methods: Two sites of 1 km² in Saint-Georges de l’Oyapock (SGO) and Cayenne
(CAY) were prospected for mosquito immature stages in December 2013. F0 females were
genotyped for 13 microsatellites and for the knockdown resistance associated mutation V1016I.
Genetic diversity and differentiation indices were obtained in Arlequin software. Genetic structure
among samples was tested in the program STRUCTURE. Evolutionary scenario probabilities and
estimates were computed in DIY-ABC.
Results: We detected the presence of two populations (k=2) congruent with each locality, with low
but significant differentiation levels. Both populations exhibited similar effective population sizes and
overall diversity. However, different evolutionary scenarios were obtained for each population. The
V1016I kdr mutation is almost fixed in CAY population while SGO exhibited a larger proportion of
heterozygotes.
Conclusion: Genetic differentiation between the two populations suggests barriers to gene flow
that may limit the exchange of resistance alleles. Therefore, the expansion of insecticide resistance
in each population may also be due to local selective pressure. Additional spatial and temporal
investigations are being conducted to confirm this hypothesis.
Distinct alterations in the sodium channel of Aedes aegypti confer different
levels of resistance to pyrethroid
L.P Brito, L.C da Silva, J.B Pereira Lima, A. Jesus Martins
Laboratório de Fisiologia e Controle de Artrópodes Vetores/ IOC/ Fiocruz
Background: Kdr mutations confer resistance to pyrethroids. We previously described two kdr
alleles in A. aegypti Brazilian populations (NaVR1 and NaVR2), considering the polymorphic sites
1016 and 1534 of the voltage gated sodium channel gene (NaV). Additionally, there were also a
series of evidence pointing to the occurrence of duplication on that gene.
Objectives: We aimed to evaluate the level of resistance to pyrethroid conferred by the kdr alleles
and the duplication in the NaV gene of A. aegypti.
Methods: We established homozygous lineages for both NaVR2 (R2R2) and NaVR1 (R1R1)
alleles, based on backcrosses between field populations and the Rockefeller strain, so that kdr
lineages shared the same genetic background without additional resistance mechanisms.
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