Abstract
Background. The intensive use of insecticides in public health and agriculture has led to the development of insecticide resistances in malaria vectors across sub-Saharan Africa countries in the last two decades. The kdr target site point mutation which is among the best characterised resistance mechanisms seems to be changing its distribution patterns on the African continent. The 1014F kdr mutation originally described only in West Africa is spreading to East Africa while the 1014S kdr mutation originally described in East Africa, is spreading to West and Central Africa. However, the East-kdr mutation has not been reported in Côte d'Ivoire so far. Methods. Immature stages of Anopheles gambiae s.l. were collected from breeding sites at the outskirts of Yamoussoukro, Côte d'Ivoire. Emerging 3-5 day old adult female mosquitoes were tested for susceptibility to deltamethrin 0.05%, malathion 5%, bendiocarb 1% and dichlorodiphenyltrichloroethane (DDT) 4% according to WHO standard procedures. A total of 50 An.gambiaes.l. specimens were drawn at random for DNA extraction and identification down to the species level. A subsample of 30 mosquitoes was tested for the East-African kdr mutation using a Taqman assay. Results. The tested mosquito population appeared to be strongly resistant to deltamethrin (1.03% mortality), bendiocarb (38.46% mortality) and DDT (0% mortality) with probable resistance observed for malathion (92.47%). Among the 41 mosquitoes that were successfully characterized, An.coluzzii was predominant (68.3%) followed by An.gambiae s.s. (19.5%) and a few hybrids (7.3%). Out of 30 specimens genotyped for East-kdr, a single hybrid mosquito appeared to be heterozygous for the mutation. Conclusion. The present study revealed the presence of the East-kdr mutation in Côte d'Ivoire for the first time in An.gambiae and highlights the urgent need to start monitoring the allele and genotype frequencies.
Highlights
The implementation of malaria control strategies, such as the spraying of residual insecticides and the use of insecticide-treated mosquito nets have led to enormous progress in the control of malaria in Sub-Saharan Africa (Hemingway, 2014)
Mosquito sampling and susceptibility testing Immature stages of An. gambiae s.l. were collected from breeding sites in October 2015 in rice fields at the outskirts of the city of Yamoussoukro (6°49′13′′ N/5°16′36′′ W) as part of a large insecticide resistance monitoring study across several cities in Côte d’Ivoire
Based on WHO criteria (WHO, 2013), the wild mosquito population of Yamoussoukro appeared to be strongly resistant to deltamethrin (1.03% mortality), bendiocarb (38.46% mortality) and DDT (0% mortality)
Summary
The implementation of malaria control strategies, such as the spraying of residual insecticides and the use of insecticide-treated mosquito nets have led to enormous progress in the control of malaria in Sub-Saharan Africa (Hemingway, 2014). Since the discovery of pyrethroids, the only compounds currently recommended for impregnation of mosquito nets owing to their efficacy and safety for humans, no alternative insecticides have been identified. This strong reliance on the same molecules is inevitably translated into a heavy pressure on the target mosquitoes, which have developed resistances to these compounds. Out of 30 specimens genotyped for East-kdr, a single hybrid mosquito appeared to be heterozygous for the mutation. The present study revealed the presence of the East-kdr mutation in Côte d’Ivoire for the first time in An. gambiae and highlights the urgent need to start monitoring the allele and genotype frequencies
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