Absence of the kdr mutation in the molecular 'M' form suggests different pyrethroid resistance mechanisms in the malaria vector mosquito Anopheles gambiae s.s.

Field tests conducted on adult Anopheles mosquitoes using standard WHO procedures, diagnostic kits and test papers in south-western Nigeria showed pyrethroid (deltamethrin and permethrin) resistance in adult populations of Anopheles gambiae sensu stricto. The knock-down resistance (kdr) mutation involved in pyrethroid resistance was only found in the molecular S form of An. gambiae s.s. even in area where both molecular M and S forms occurred in sympatry. The absence of the kdr mutation in the M form suggests an additional pyrethroid resistance mechanism in An. gambiae s.s.