Studies of reservoirs and vectors of plague in Northeastern, Tanzania

Abstract

Background: Since 2011, theNMCPof Benin has implemented a large IRS campaign using bendiocarb in the department of Atacora in Benin. The aim of this study was to evaluate the susceptibility of An. gambiae mosquitoes to bendiocarb, before (2010) and after (2012) the implementation of IRS interventions and to report the evolution of Ace-1R mutation frequency in this region. Methods & Materials: Mosquitoes resting in the house (indoor collection) were collected through Morning Spray Catch (MSC) from 7 a.m. to 9 a.m in five treated districts (Kouande, Natitingou, Materi, Pehunco, Tanguieta) and in the Control (Copargo, an untreated district) before and after IRS. Anopheles larvae were also reared in each district before and after IRS and emerging adults were exposed to WHO impregnated papersdiscriminating dosages with bendiocarb, 0.1%. PCR assays were run to determine themembers of the An. gambiae complex, aswell as phenotypes for insensitive acetylcholinesterase (AChE1) due to Ace-1R mutation. Results: This study showed that the mean Ace-1 mutation frequency have significantly increased from 2010 to 2012 after two years of IRS campaign. Mortality data indicated that mosquitoes were susceptible in 2010 to bendiocarb 0.1%. From 2010 to 2012, after two years of IRS campaign, there is a drastic decline in the An. gambiae susceptibility to bendiocarb in treated districts. The Ace-1R mutation was found in An. gambiae s.s. and An. coluzzi with frequency of7.33%and 7.35%.The high proportion of homozygous susceptible specimens survived from theWHO bioassays may suggest the implication of the other mechanisms of resistance such as biochemical resistance mechanisms. Conclusion: These results are of prime importance in the effort to document multiple impacts of operational control program on mosquito vectors. It showed a significant increase of Ace-1 allele frequency and resistance to bendiocarb in Anophele gambiae population after IRS implementation that can be a threat for malaria vector control based on the IRS which is in progress in Benin.