Effects of the kdr resistance mutation on the susceptibility of wild Anopheles gambiae populations to Plasmodium falciparum: a hindrance for vector control
1 G4 Group, Institut Pasteur International Network, Institut Pasteur de Bangui, Bangui BP 923, Central African Republic
2 Afrique One, Centre Suisse de recherché Scientifiques, Abidjan 01 BP 1303, Côte d’Ivoire
3 Departement of Animal Biology, Cheikh Anta Diop University, Dakar LEVP PO Box 5005 Fann, Sénégal
4 Medical Research Concil Unit The Gambia Atlantic Boulevard, Banjul PO Box 273 Fajara, The Gambia
5 Laboratoire de Paludologie et de Zoologie Médicale, Campus UCAD-IRD, Dakar BP 1386, The Gambia
6 Unité Epidémiologie, Institut Pasteur de Dakar, Dakar, Sénégal
Malaria Journal 2014, 13:340 doi:10.1186/1475-2875-13-340Published: 30 August 2014
In the context of generalization of insecticide resistance, the hypothesis that insecticide resistance has a positive impact on the capacity of mosquitoes to transmit malaria constitutes a hindrance for malaria elimination. The aim of this study was to investigated populations of Anopheles coluzzii and Anopheles gambiae S molecular form to assess whether different genotypes at the kdr locus are responsible for different susceptibility to Plasmodium falciparum infection.
F3 progeny of An. gambiae s.l. collected in Dielmo were infected by direct membrane feeding with P. falciparum gametocyte-containing blood sampled from volunteer patients. The presence of oocysts was determined by light microscopy after seven days, and the presence of sporozoites by ELISA after 14 days. Mosquito species and molecular forms were identified by PCR. Generalized linear models were performed using the R software to test the effect of explanatory variables including the genotype at the kdr locus on infection rate and density.
The odds of being infected with oocysts and sporozoites were greater in RS and RR groups than in SS groups (χ2 = 42.8, df = 1, P(>χ2) = 6.1e-11). The density of infection was also dependent on genotype, with RR and RS genotypes showing denser infection than SS genotypes. Pairwise comparisons of oocyst number and absorbance indicated sometime a small betwen species (i.e. between An. gambiae S form, and An. coluzzii), but the effect of genotype was much more important.
The presence of the resistance allele at the kdr locus increases susceptibility to Plasmodium not only at the oocyst stage but also at the sporozoite stage in non-genetically modified wild mosquitoes. These results have significant implications and should be taken into account in the development of strategies for malaria control.