Distribution of insensitive acetylcholinesterase (ace-1R) in Anopheles gambiae s.l. populations from Burkina Faso (West Africa)

To investigate through countrywide sampling at 20 localities across the three different agro-climatic zones of Burkina Faso, the distribution of the acetylcholinesterase insensitive mutation ace-1(R), which confers resistance to organophosphates (OP) and carbamates (CM) insecticides in An. gambiae s.l. Adult mosquitoes were collected by indoor aerosol spraying from August to October 2006. Specimens were identified to species by polymerase chain reaction (PCR) assay and characterized for the ace-1(R) mutation using a PCR-restriction fragment length polymorphism diagnostic. Collected mosquitoes were a mixture of An. gambiae s.s. and An. arabiensis across the Sudan (98.3%vs. 1.7%), Sudan-sahelian (78.6%vs. 21.4%) and the Sahel (91.5%vs. 8.5%) ecotypes. The An. gambiae S-form predominated in the Sudan sites from the West (69%vs. 31% for the M form) but was not found in the Sahel (100% M form). The ace-1(R) mutation was dispersed throughout the Sudan and Sudan-sahelian localities at moderate frequency (< 50%) but was absent in the Sahel. It was far more prevalent in S form than M form mosquitoes (0.32 for the S form vs. 0.036 for the M form). No An. arabiensis was detected carrying the mutation. The geographic distribution of ace-1(R) in the Sudan and Sudan-sahelian correlated with the cotton growing areas dispersed throughout the two climatic zones. These results have special significance as OP and CM insecticides have been proposed as alternatives or additions to pyrethroids which are currently used exclusively in many vector control programmes.