OBJECTIVETo investigate the genotypes , allele frequencies and dynamic distribution on resistance associated esterase genes of Culex pipiens complex in Hangzhou.

METHODSThe PCR-restriction fragment length polymorphism (PCR-RFLP) assay was applied to type the resistance associated esterase genes, and dynamic surveillance on frequencies of the resistance associated esterase gene of natural population of Culex pipiens complex in Hangzhou during 2003-2005, and phenotype of the resistance associated esterase genes were detected by esterase starch gel electrophoresis technique.

RESULTSThe PCR-RFLP assay of esterase allele genes for three consecutive years disclosed four esterase genotypes, namely, the world-wide highly active homozygous Est beta 1(1) (50%-54%), homozygous Est beta 2 (29%-34%), heterozygous Est beta 1(1)/beta 2 (5%-10%) and Est beta N (3.13%) of a new homozygous genotype. The research of the resistance associated esterase genes phenotype in natural population of Culex pipiens complex in Hangzhou in 2005 with esterase starch gel electrophoresis technique revealed four major types, namely, Est beta 1(1) (61%), Est alpha 2/beta 2 (12%), Est alpha 8/beta 8 (7%) and sensitive phenotype (29%).

CONCLUSIONThere should be various resistance associated esterase genotypes in natural population of Culex pipiens complex in Hangzhou. During the period of 2003-2005, Est beta 1(1) was the major type; Est alpha 2/beta 2 was the second. Est beta N was a new esterase genotype detected in 2005 only with a mere percentage of 3.13%. As for its resistance to the new insecticide, a follow-up study should be needed. The molecular typing of the amplified esterase gene should be consistent with the resistance associated esterase genes phenotype.