Abstract
The Asian mosquito, Aedes albopictus (Skuse), is an invasive mosquito which has become one of the most important vectors of dengue, Zika, and chikungunya viruses worldwide. This species was reported for the first time in Cameroon in early 2000s and became the dominant Aedes species in the urban areas in the southern part of Cameroon but remain poorly characterized. Here, we assessed the susceptibility profile of A. albopictus collected throughout Cameroon and investigated the potential resistance mechanisms involved. Immature stages of A. albopictus were collected between March and July 2017 in 15 locations across Cameroon and reared until G1/G2 generation. Larval, adult bioassays, and synergists [piperonyl butoxide (PBO) and diethyl maleate (DEM)] assays were carried out according to WHO recommendations. F1534C mutation was genotyped in field collected adults (Go) using allele specific PCR. All tested populations were susceptible to both larvicides, temephos and Bacillus thuringiensis israelensis (Bti), after larval bioassays. Adult bioassays revealed a high level of resistance of A. albopictus to 4% DDT with mortality rates ranging from 12.42% in Bafang to 75.04% in Kumba. The resistance was reported also in 0.05% deltamethrin, 0.25% permethrin, and 0.1% propoxur in some locations. A loss of susceptibility to 0.1% bendiocarb was found in one of three populations analysed. A full susceptibility to 1% fenitrothion were observed across the country. A full recovery or partial of susceptibility was observed in A. albopictus when pre-exposed to PBO or DEM and then to DDT and permethrin, respectively. The F1534C kdr mutation was not detected in A. albopictus. This study showed that the susceptibility profile of A. albopictus to insecticide vary according to the sampling location and insecticides used. These findings are useful to planning vector control program against arbovirus vectors in Cameroon and can be used as baseline data for further researches.
Highlights
The Asian tiger mosquito, Aedes albopictus (Skuse) 1894, originated from South East Asia has invaded all the five continents during the past four decades [1]
Analysis revealed that for both larvicides and populations tested, RR50 and RR95 were less than 5 suggesting that A. albopictus from these locations are susceptible to Bacillus thuringiensis israelensis (Bti) and temephos
Bioassays performed with susceptible strain revealed that this A. albopictus strain was fully susceptible to almost all insecticides tested excepted DDT for which 80.7% mortality rate were found
Summary
The Asian tiger mosquito, Aedes albopictus (Skuse) 1894, originated from South East Asia has invaded all the five continents during the past four decades [1]. This mosquito species is one of the most important vectors of several arboviruses including dengue virus (DENV, Flaviviridae, Flavivirus) [2], chikungunya virus (CHIKV, Togaviridae, Alphavirus) and Zika virus (ZIKV, Flaviviridae, Flavivirus) [3,4] worldwide. In Cameroon A. albopictus is the dominant Aedes species in most cities located under 6 N latitude [16]. It was recently demonstrated that A. albopictus populations collected in different ecological settings in Cameroon are able to transmit dengue 2 virus [17]
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