Alou L. P. A., Koffi A. A., Adja M. A., Tia E., Kouassi P. K., Kone M., Chandre Fabrice. (2010). Distribution of ace-1(R) and resistance to carbamates and organophosphates in Anopheles gambiae s.s. populations from Cote d'Ivoire. Malaria Journal, 9, p. 167. ISSN 1475-2875.
Titre du document
Distribution of ace-1(R) and resistance to carbamates and organophosphates in Anopheles gambiae s.s. populations from Cote d'Ivoire
Alou L. P. A., Koffi A. A., Adja M. A., Tia E., Kouassi P. K., Kone M., Chandre Fabrice
Source
Malaria Journal, 2010,
9, p. 167 ISSN 1475-2875
Background: The spread of pyrethroid resistance in Anopheles gambiae s.s. is a critical issue for malaria vector control based on the use of insecticide-treated nets. Carbamates and organophosphates insecticides are regarded as alternatives or supplements to pyrethroids used in nets treatment. It is, therefore, essential to investigate on the susceptibility of pyrethroid resistant populations of An. gambiae s.s. to these alternative products. Methods: In September 2004, a cross sectional survey was conducted in six localities in Cote d'Ivoire: Toumbokro, Yamoussoukro, Toumodi in the Southern Guinea savannah, Tiassale in semi-deciduous forest, then Nieky and Abidjan in evergreen forest area. An. gambiae populations from these localities were previously reported to be highly resistant to pyrethroids insecticides. Anopheline larvae were collected from the field and reared to adults. Resistance/susceptibility to carbamates (0.4% carbosulfan, 0.1% propoxur) and organophosphates (0.4% chlorpyrifos-methyl, 1% fenitrothion) was assessed using WHO bioassay test kits for adult mosquitoes. Then, PCR assays were run to determine the molecular forms (M) and (S), as well as phenotypes for insensitive acetylcholinesterase (AChE1) due to G119S mutation. Results: Bioassays showed carbamates (carbosulfan and propoxur) resistance in all tested populations of An. gambiae s.s. In addition, two out of the six tested populations (Toumodi and Tiassale) were also resistant to organophosphates (mortality rates ranged from 29.5% to 93.3%). The M-form was predominant in tested samples (91.8%). M and S molecular forms were sympatric at two localities but no M/S hybrids were detected. The highest proportion of S-form (7.9% of An. gambiae identified) was in sample from Toumbokro, in the southern Guinea savannah. The G119S mutation was found in both M and S molecular forms with frequency from 30.9 to 35.2%. Conclusion: This study revealed a wide distribution of insensitive acetylcholinesterase due to the G119S mutation in both M and S molecular forms of the populations of An. gambiae s.s. tested. The low cross-resistance between carbamates and organophosphates highly suggests involvement of other resistance mechanisms such as metabolic detoxification or F290V mutation.
