MOLECULAR CHARACTERIZATION OF PYRETHROID KNOCKDOWN RESISTANCE (KDR) IN THE MAJOR MALARIA VECTOR ANOPHELES-GAMBIAE S.S

Pyrethroid-impregnated bednets are playing an increasing role for comb ating malaria, especially in stable malaria areas. More than 90% of th e current annual malaria incidence (c. 500 million clinical cases with up to 2 million deaths) is in Africa where the major vector is Anophe les gambiae s.s. As pyrethroid resistance has been reported in this mo squito, reliable and simple techniques are urgently needed to characte rize and monitor this resistance in the field, In insects, an importan t mechanism of pyrethroid resistance is due to a modification of the v oltage-gated sodium channel protein recently shown to be associated wi th mutations of the para-type sodium channel gene. We demonstrate here that one of these mutations is present in certain strains of pyrethro id resistant A. gambiae s.s. and describe a PCR-based diagnostic test allowing its detection in the genome of single mosquitoes, Using this test, we found this mutation in six out of seven field samples from We st Africa, its frequency being closely correlated with survival to pyr ethroid exposure. This diagnostic test should bring major improvement for field monitoring of pyrethroid resistance, within the framework of malaria control programmes.