Study of malaria vector, kdr and ace 1 gene mutations in two eco-climatic zones of Mauritania

Background

Anopheles mosquitoes belonging to Anopheles gambiae complex are the main malaria vector in Mauritania but data on their vector capacities, their feeding habits and insecticides susceptibility are scarce. Therefore, the objectives of this study were to fill this gap.

Material and Methods

The study was conducted during the rainy season of 2009 and 2010 in two eco-climatic zones of Mauritania: Nouakchott (Saharan zone) and Hodh Elgharbi region (Sahelian zone). Adult mosquitoes were sampled by indoor residual spraying. They were identified morphologically and then molecularly using polymerase chain reaction. Anopheles females were tested by ELISA for the presence of Plasmodium circumsporozoite protein (CSP) of Plasmodium falciparum and P. vivax VK210 and VK247. Each positive sample was then confirmed by PCR. A blood meal identification was also realized in all engorged females by cytochrome b gene analyse. Molecular assessments of pyrethroid knock down (kdr) resistance and of insensitive acetylcholinesterase resistance were conducted.

Results

In Nouakchott, the unique anopheles species identified during the survey was Anopheles arabiensis (350 specimens). In Hodh Elgharbi, 1092 anopheles specimens were collected including 578(52.9%) Anopheles rufipes, 486(44.5%) Anopheles arabiensis, 20(1.8%) Anopheles gambiae s.s, 5(0.4%) Anopheles pharoensis and 3(0.2%) Anopheles funestus. Three (1.6%) parous female An arabiensis from Nouakchott were found positive with Plasmodium vivax VK210 by Elisa but PCR confirmed the infection by P. vivax of only one of them. In Hodh Elgharbi no mosquito was found positive for Plasmodium infection. There was a statistically significant difference between the percentage of human blood fed anopheles in Nouakchott (47.7%, 52 of 109 blood-engorged females An. arabiensis) and in Hodh Elgharbi (15.1%, 5 of 33 blood-engorged mosquitoes) (P < 0.001, Fisher’s exact test). Analysis of the kdr polymorphisms pointed out 37.6%(70/186) of East African kdr mutation (L1014S) in Nouakchott versus 9%(4/43) in Hodh Elgharbi region (P <0.001). Nevertheless West (L1014F) African kdr mutation was found only in An. gambiae populations from Hodh Elgharbi region: 6.9%(3/43). No ace 1mutation was founded in mosquito’s specimens from the two study zones.

Conclusions

Overall, this study confirmed the presence of autochthonous vivax malaria transmission in Nouakchott, described for the first time, the absence of ace 1 mutation, the presence of both West and East African kdr mutation in An. gambiae in Mauritania and highlighted the regional variations in prevalence and type of kdrmutations.

Key words: Anopheles arabiensis, Anopheles gambiae s.s., ELISA, Blood meal, PCR, Plasmodium vivaxVK210, Nouakchott, Hodh Elgharbi, Mauritania