Dataset Information

Effective population size of Anopheles funestus chromosomal forms in Burkina Faso.

ABSTRACT: As Anopheles funestus is one of the principal Afro-tropical malaria vectors, a more complete understanding of its population structure is desirable. In West and Central Africa, An. funestus population structure is complicated by the coexistence of two assortatively mating chromosomal forms. Effective population size (Ne) is a key parameter in understanding patterns and levels of intraspecific variation, as it reflects the role of genetic drift. Here, Ne was estimated from both chromosomal forms, Kiribina and Folonzo, in Burkina Faso.Short-term Ne was estimated by evaluating variation at 16 microsatellite loci across temporal samples collected annually from 2000-2002. Estimates were based on standardized variance in allele frequencies or a maximum likelihood method. Long-term Ne was estimated from genetic diversity estimates using mtDNA sequences and microsatellites.For both forms, short-term and long-term Ne estimates were on the order of 10(3) and 10(5), respectively. Long-term Ne estimates were larger when based on loci from chromosome 3R (both inside and outside of inversions) than loci outside of this arm.Ne values indicate that An. funestus is not subject to seasonal bottlenecks. Though not statistically different because of large and overlapping confidence intervals, short-term Ne estimates were consistently smaller for Kiribina than Folonzo, possibly due to exploitation of different breeding sites: permanent for Folonzo and intermittent for Kiribina. The higher long-term Ne estimates on 3R, the arm carrying the two inversions mainly responsible for defining the chromosomal forms, give natural selection broader scope and merit further study.

SUBMITTER: Michel AP

PROVIDER: S-EPMC1676016 | biostudies-literature | 2006 Nov

REPOSITORIES: biostudies-literature

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Effective population size of Anopheles funestus chromosomal forms in Burkina Faso.

Michel Andrew P AP Grushko Olga O Guelbeogo Wamdaogo M WM Sagnon N'fale N Costantini Carlo C Besansky Nora J NJ

Malaria journal 20061124

<h4>Background</h4>As Anopheles funestus is one of the principal Afro-tropical malaria vectors, a more complete understanding of its population structure is desirable. In West and Central Africa, An. funestus population structure is complicated by the coexistence of two assortatively mating chromosomal forms. Effective population size (Ne) is a key parameter in understanding patterns and levels of intraspecific variation, as it reflects the role of genetic drift. Here, Ne was estimated from both ...[more]

PMID: 17125511

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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.

Project description:BackgroundTwenty-seven villages were selected in southwest Burkina Faso to implement new vector control strategies in addition to long lasting insecticidal nets (LLINs) through a Randomized Controlled Trial (RCT). We conducted entomological surveys in the villages during the dry cold season (January 2017), dry hot season (March 2017) and rainy season (June 2017) to describe malaria vectors bionomics, insecticide resistance and transmission prior to this trial.MethodsWe carried out hourly catches (from 17:00 to 09:00) inside and outside 4 houses in each village using the Human Landing Catch technique. Mosquitoes were identified using morphological taxonomic keys. Specimens belonging to the Anopheles gambiae complex and Anopheles funestus group were identified using molecular techniques as well as detection of Plasmodium falciparum infection and insecticide resistance target-site mutations.ResultsEight Anopheles species were detected in the area. Anopheles funestus s.s was the main vector during the dry cold season. It was replaced by Anopheles coluzzii during the dry hot season whereas An. coluzzii and An. gambiae s.s. were the dominant species during the rainy season. Species composition of the Anopheles population varied significantly among seasons. All insecticide resistance mechanisms (kdr-w, kdr-e and ace-1 target site mutations) investigated were found in each members of the An. gambiae complex but at different frequencies. We observed early and late biting phenotypes in the main malaria vector species. Entomological inoculation rates were 2.61, 2.67 and 11.25 infected bites per human per month during dry cold season, dry hot season and rainy season, respectively.ConclusionThe entomological indicators of malaria transmission were high despite the universal coverage with LLINs. We detected early and late biting phenotypes in the main malaria vector species as well as physiological insecticide resistance mechanisms. These data will be used to evaluate the impact of complementary tools to LLINs in an upcoming RCT.

Dataset Information

Effective population size of Anopheles funestus chromosomal forms in Burkina Faso.

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Effective population size of Anopheles funestus chromosomal forms in Burkina Faso.

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