DETERMINATION OF ACE.1 GENOTYPES IN SINGLE MOSQUITOS - TOWARD AN ECUMENICAL BIOCHEMICAL TEST

The occurrence of two acetylcholinesterases, AChE1 and AChE2, in the m osquito Culex pipiens has been recently documented, Resistance to orga nophosphates and carbamates due to target insensitivity is the result of a qualitative change of only AChE1, encoded by the Ace.1 gene, Beca use AChE1 and AChE2 differ in their sensitivity to inhibitors, Ace.1 g enotypes can be misclassified by previous tests. We describe a new rap id microplate Lest that allows unambiguous identification of Ace.1 gen otypes. This test involves comparing AChE activities in the absence of insecticide and in the presence of two propoxur concentrations: a low concentration that inhibits only the sensitive AChE1 and a higher con centration that inhibits also AChE2 but not the insensitive AChE1 resp onsible of insecticide resistance. This comparison allows the identifi cation of the three Ace.1 genotypes: resistant (Ace.1(RR)), susceptibl e (Ace.1(SS)) homozygotes, and heterozygotes (Ace.1(RS)), The similari ty of propoxur sensitivity of modified AChE1s found in various resista nt strains From the United States, Europe, and Africa indicates that t his test is probably suitable for all the Ace.1 alleles described so f ar in C. pipiens. (C) 1996 Academic Press, Inc.