Dataset Information

Variation in Pyrethroid Resistance Phenotypes in Anopheles darlingi in an Area with Residual Malaria Transmission: Warning of Suspected Resistance in French Guiana.

ABSTRACT: Anopheles darlingi is the main vector of malaria in South America. In French Guiana, malaria transmission occurs inland and along the rivers with a regular reemergence in the lower Oyapock area. Control against malaria vectors includes indoor residual spraying of deltamethrin and the distribution of long-lasting impregnated bednets. In this context, the level of resistance to pyrethroids was monitored for 4 years using CDC bottle tests in An. darlingi populations. A loss of susceptibility to pyrethroids was recorded with 30-minute knock-down measured as low as 81%. However, no pyrethroid molecular resistance was found by sequencing a 170 base pair fragment of the S6 segment of domain II of the voltage-gated sodium channel gene. Fluctuation of resistance phenotypes may be influenced by the reintroduction of susceptible alleles from sylvatic populations or by other mechanisms of metabolic resistance.

SUBMITTER: Vezenegho S

PROVIDER: S-EPMC9896345 | biostudies-literature | 2023 Feb

REPOSITORIES: biostudies-literature

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Variation in Pyrethroid Resistance Phenotypes in Anopheles darlingi in an Area with Residual Malaria Transmission: Warning of Suspected Resistance in French Guiana.

Vezenegho Samuel S Carinci Romuald R Issaly Jean J Nguyen Christophe C Gaborit Pascal P Ferraro Laetitia L Lacour Guillaume G Mosnier Emilie E Pommier de Santi Vincent V Epelboin Yanouk Y Girod Romain R Briolant Sebastien S Dusfour Isabelle I

The American journal of tropical medicine and hygiene 20221219 2

Anopheles darlingi is the main vector of malaria in South America. In French Guiana, malaria transmission occurs inland and along the rivers with a regular reemergence in the lower Oyapock area. Control against malaria vectors includes indoor residual spraying of deltamethrin and the distribution of long-lasting impregnated bednets. In this context, the level of resistance to pyrethroids was monitored for 4 years using CDC bottle tests in An. darlingi populations. A loss of susceptibility to pyr ...[more]

PMID: 36535248

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Project description:BackgroundWith an Annual Parasite Incidence (API) of 132.1, in the high and moderate risks zones, the Maroni area of French Guiana has the second highest malaria incidence of South-America after Guyana (API = 183.54) and far above Brazil (API = 28.25). Malaria transmission is occurring despite strong medical assistance and active vector control, based on general WHO recommendations. This situation is generated by two main factors that are the social and cultural characteristics of this border area, where several ethnic groups are living, and the lack of understanding of transmission dynamics of the main mosquito vector, Anopheles darlingi. In this context, entomological data collected in two villages belonging to two different ethnic groups of the French border of the Maroni River, were retrospectively analysed to find out how the mosquito bionomics are related to the malaria transmission patterns.MethodsData were provided by human landing catches of mosquitoes carried out each month for two years in two villages belonging to two ethnic groups, the Amerindians Wayanas and the Aloukous of African origin. The mosquitoes were sorted by species, sex, date, hour and place of collection and processed for Plasmodium sp. parasite detection. The data were compiled to provide the following variables: human biting rates (HBR), parity rates (PR), numbers of infective bites (IB), entomological inoculation rates (EIR) and numbers of infected mosquitoes surviving enough to transmit (IMT). Spatial and temporal differences of variables between locations and during the night were tested by the Kruskall-Wallis analysis of variance to find out significant variations.ResultsThe populations of the main mosquito vector An. darlingi showed significant variations in the spatial and temporal HBR/person/night and HBR/person/hour, IB/person/month and IB/person/hour, and IMT/village/night and IMT/village/hour. In the village of Loca (Aloukous), the IMT peaked from June to August with a very low transmission during the other months. The risks were higher during the first part of the night and an EIR of 10 infective bites per person and per year was estimated. In the village of Twenke (Wayanas), high level of transmission was reported all year with small peaks in March and October. The risk was higher during the second part of the night and an EIR of 5 infective bites per person and per year was estimated.ConclusionFor the first time in the past 40 years, the mosquito bionomics was related to the malaria transmission patterns in French Guiana. The peak of malaria cases reported from August to October in the Maroni region is concomitant with the significant peak of An. darlingi IMT, reported from the village of Loca where transmission is higher. However, the persistent number of cases reported all year long may also be related to the transmission in the Amerindian villages. The An. darlingi bionomics for these two close populations were found significantly different and may explain why a uniform vector control method is inadequate. Following these findings, malaria prevention measures adapted to the local conditions are needed. Finally, the question of the presence of An. darlingi sub-species is raised.

Project description:BackgroundThe susceptibility status of Anopheles funestus to insecticides remains largely unknown in most parts of Africa because of the difficulty in rearing field-caught mosquitoes of this malaria vector. Here we report the susceptibility status of the An. funestus population from Tororo district in Uganda and a preliminary characterisation of the putative resistance mechanisms involved.Methodology/principal findingsA new forced egg laying technique used in this study significantly increased the numbers of field-caught females laying eggs and generated more than 4000 F1 adults. WHO bioassays indicated that An. funestus in Tororo is resistant to pyrethroids (62% mortality after 1 h exposure to 0.75% permethrin and 28% mortality to 0.05% deltamethrin). Suspected DDT resistance was also observed with 82% mortality. However this population is fully susceptible to bendiocarb (carbamate), malathion (organophosphate) and dieldrin with 100% mortality observed after exposure to each of these insecticides. Sequencing of a fragment of the sodium channel gene containing the 1014 codon conferring pyrethroid/DDT resistance in An. gambiae did not detect the L1014F kdr mutation but a correlation between haplotypes and resistance phenotype was observed indicating that mutations in other exons may be conferring the knockdown resistance in this species. Biochemical assays suggest that resistance in this population is mediated by metabolic resistance with elevated level of GSTs, P450s and pNPA compared to a susceptible strain of Anopheles gambiae. RT-PCR further confirmed the involvement of P450s with a 12-fold over-expression of CYP6P9b in the Tororo population compared to the fully susceptible laboratory colony FANG.ConclusionThis study represents the first report of pyrethroid/DDT resistance in An. funestus from East Africa. With resistance already reported in southern and West Africa, this indicates that resistance in An. funestus may be more widespread than previously assumed and therefore this should be taken into account for the implementation and management of vector control programs in Africa.

Dataset Information

Variation in Pyrethroid Resistance Phenotypes in Anopheles darlingi in an Area with Residual Malaria Transmission: Warning of Suspected Resistance in French Guiana.

Publications

Variation in Pyrethroid Resistance Phenotypes in Anopheles darlingi in an Area with Residual Malaria Transmission: Warning of Suspected Resistance in French Guiana.

Similar Datasets

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