[A biochemical method for the determination of the altered acetylcholinesterase which confers resistance to organophosphate and carbamate insecticides in Culex quinquefasciatus Say, 1823].

The application of a rapid technique to determine the frequency of the altered acetylcholinesterase gene which confers cross resistance to organophosphate and carbamate insecticides to mosquitoes, was tested. Laboratory strains of Culex quinquefasciatus Say, 1823 were used to apply this technique: A clear differentiation in absorbance values was attained among resistant susceptible homozygous mosquitoes (SS), heterozygous (RS); and homozygous (RR), with residual enzymatic activity values of 10-60; 70-100; and 80-120, respectively. This was clearly differentiated at first sight due to a change of the reaction's yellow color. The gene of the altered acetylcholinesterase was found in the Culex quinquefasciatus strains under study.