DISTRIBUTION OF ORGANOPHOSPHATE AND CARBAMATE RESISTANCE IN CULEX-PIPIENS QUINQUEFASCIATUS (DIPTERA, CULICIDAE) IN WEST-AFRICA

The distribution of organophosphate and carbamate resistance was inves tigated in 33 samples of Culex pipiens quinquefasciatus Say from 25 ci ties in Cote d'Ivoire and Burkina Faso. Organophosphate resistance lev els were higher in Cote d'Ivoire than in Burkina Faso. Chlorpyrifos re sistance ratios at LC95 ranged from 4 to 30 times in Cote d'Ivoire and from 3 to 6 times in Burkina Faso. For temephos, ratios ranged from 3 to 18 and from 1 to 2, respectively. Of 27 samples from Cote d'Ivoire , 25 also displayed cross resistance to carbamates as shown by a morta lity plateau in bioassays with propoxur and carbosulfan (similar to ch lorpyrifos). Cross resistance to organophosphates and carbamates was c aused by an insensitive acetylcholinesterase allele (Ace(R)). This gen e was absent from Burkina Faso, except in Niangoloko near the Cote d'I voire border. Organophosphate resistance also was associated with the presence of A2-B2 overproduced esterases which had higher frequencies in Cote d'Ivoire (75-100%) than in Burkina Faso (40-50%). Two other es terases with the same electrophoretic mobility as C2 from Puerto Rico and B1 from California were identified for the 1st time in West Africa . ''C2'' was widespread, whereas ''B1'' was present in only a few mosq uitoes from Cote d'Ivoire. These differences in resistance patterns sh ould be taken into consideration in planning urban mosquito control st rategies within 2 countries.