[Assessing the insecticide resistance of an Aedes aegypti strain in El Salvador].
OBJECTIVE
To assess the level of insecticide susceptibility of a certain Aedes aegypti strain found in El Salvador and to explain the mechanisms for its resistance to temephos.


METHODS
An A. aegypti strain from the municipality of Soyapango, Department of San Salvador, El Salvador, was studied. Bioassays were used to determine the susceptibility of the larvae to the organophosphate insecticide temephos and to three pyrethroids (deltamethrin, lambda-cyhalothrin, and cypermethrin); and of adults to an organophosphate insecticide (chlorpyrifos). The resistance factor (RF50) with determined with respect to a reference susceptible strain (Rockefeller). The mechanism of temephos resistance was determined through the use of synergistic substances, biochemical assays for enzymatic activity, and polyacrylamide gel zymograms.


RESULTS
The larvae of the strain studied proved highly resistant to temephos (RF50 = 24.16). Of the enzyme samples analyzed, only the esterase A4 was linked to the mechanism of temephos resistance. The adult mosquitoes were susceptible to lambda-cyhalothrin and chlorpyrifos; and resistance to deltamethrin and cypermethrin fell into the category needing further verification.


CONCLUSIONS
Temephos resistance could reduce the efficiency of chemical control of the A. aegypti mosquito in El Salvador study area. Chlorpyrifos, lambda-cyhalothrin, and cypermethrin are good alternative insecticides for use in new efforts to control this vector.
Lazcano
Juan A Bisset
JA
Instituto de Medicina Tropical Pedro Kourí, Ciudad de La Habana, Cuba. bisset@ipk.sld.cu
Rodríguez
María M
MM
San Martín
José L
JL
Romero
José E
JE
Montoya
Romeo
R
D000330:Aedes / Q000187:drug effects*; D000818:Animals; D004544:El Salvador; D007305:Insecticide Resistance