Phenotypic and genetic susceptibility patterns of Anopheles gambiae s.l. mosquitoes to carbamates in selected districts of Uganda

Abstract

Despite the global decline in malaria cases, the malaria incident rate remains high in sub-Saharan Africa. The major remedy to deal with malaria has been the control of malaria vectors through use of insecticides treated nets (ITNs) and indoor residue sprays. However, this remedy is being counteracted by the threatening emergency of insecticide resistance to different classes of insecticides among mosquito populations. Moreover, in Uganda, in most of the parts of the country there is a near fixation of the

genes known to confirm resistance to pyrethroids (commonly used insecticide in Long- Lasting Insecticidal Nets [LLINs]) in most mosquito vectors. To end this, there have

been a suggestion as well as implemented changes from the use of pyrethroids to carbamates. Unfortunately, resistance to carbamates has also been observed and fully confirmed elsewhere in Africa. Resolutely, before full implementation of the use of carbamates there is need to understand mosquito susceptibility patterns to this class of insecticide and the allele frequency of G119S mutation in the ace-1 (gene that confers mosquito resistance to carbamates) in our population. This study aimed at determining susceptibility patterns and the allele frequency of the G119S mutation in the ace-1 gene. Anopheles gambiae (s.l.) collected from four different districts of Adjumani, Koboko, Moyo, and Mubende found Uganda were exposed to the diagnostic concentration of bendiocarb using WHO mosquito insecticide bioassays. The mortality rate was calculated using Abbott’s formula. Genomic DNA from mosquito abdomen was then extracted and rhAmp SNP genotyping was performed to detect the G119S 1 mutation in the ace-1 gene. The allele frequency was then calculated among the mosquito population. Mosquitoes from all study sites were resistant to the diagnostic concentration of bendiocarb with overall mortality of 81.21% (Adjumani,78.48%; Koboko,79.05%; Moyo, 84.03%; and Mubende, 82.41%). The overall allele frequency of G119S mutation (ace-1 R ) was found to be 2.84% (Adjumani,4.55%; Koboko,0.00%; Moyo, 2.44%; and Mubende, 2.84%). This study suggests that rigorous further studies should be done to fully characterize the distribution of this resistance among different species of Anopheles gambiae (s.l.) complex as well as other malaria mosquito vectors. Policy makers should consider implementing enhanced insecticide resistance surveillance in these studied areas before, during and after implementation of IRS with bendiocarb (carbamates).