Resistance Monitoring in Culex pipiens (Diptera: Culicidae) from Central-Eastern France

Abstract

Insensitive acetylcholinesterase (AceR) and five over-produced esterases (A1, A2 and B2, and A4 and B4) involved in detoxification are responsible for resistance to organophosphorous insecticides (OPs) in Culex pipiens L. from the Rhône-Alpes region, where C. pipiens control is mainly accomplished with the OPs temephos and chlorpyrifos using 0.15 mg/liter doses. The strong linkage disequilibria observed between esterases A1 and Est-20(0.64), esterases A4 and B4, and esterases A2 and B2 indicate that these genes were introduced in the Rhône-Alpes region. AceR and esterase A1, which appeared in the south of France 3 yr before the start of mosquito control in Rhône-Alpes, had the highest frequencies. All resistant genotypes were shown to be killed by 0.15 mg/liter temephos in natural breeding sites, but not by 0.15 mg/liter chlorpyrifos. These results are discussed in relation with mosquito control strategies.

POPULATION STRUCTURE AND DYNAMICS OF SELECTED GENES IN THE MOSQUITOCULEX PIPIENS

“…Esterase AI, observed in all transects with a mean frequency of 0.16, was significantly associated with treated areas in transects I and J, but not in transect K (table 3). Esterases A2 and B2 were always found together, as in every previous survey (Rivet et al 1993(Rivet et al , 1994. They were detected in four samples from the I and K transects, with a mean frequency in these samples of 11%.…”

“…In France, the coast from 18 to 112 is treated with OP insecticides (mainly chlorpyrifos, temephos, and fenitrothion); from 113 to the Italian border, treatments are sparse and occasional. On the J transect, treatments are occasional in the south (11-13) and intensive and recent around Lyon (J5b-J6), where temephos is mainly used (Rivet et al 1994). Transect K runs across the coastal areas with intensively treated OP (Kl-K4) and goes into the untreated inland (K5-K9).…”

“…Control programs against Culex pipiens were initiated in other regions of France, Italy, and northern Spain during the seventies and early eighties (Villani et al 1982;Consell comareal del baix Llabregat 1989;Sinegre et al 1976;Rivet et al 1994), all using OP insecticides. Whenever genetic surveys were conducted on these more recently treated areas, the resistance genes detected were the same as those of southern France (Villani et al 1982;Severini et al 1993Severini et al , 1994Rivet et lao 1994;Raymond and Marquine 1994;Raymond and Pasteur unpubl.…”

“…data). The only exception was the esterase named C1, which has only been found in Corsica and the central part of eastern France (Raymond and Marquine 1994;Rivet et al 1994).…”

Insecticide Resistance and Vector Control

“…However, in the northern province of Esmeraldas, where insecticide use had been limited and an epidemic of Plasmodium falciparum malaria was under way, populations were completely susceptible. Lack of insecticide use does not preclude immigration of resistance genes (e.g., the movement of esterase resistance to OPs in C. pipiens into certain areas of France [64]). …”