Resistance to organophosphorus insecticides found in Aedes aegypti (Diptera: Culicidae) from Santiago de Cuba, 1997-2009.
INTRODUCTION: resistance to organophosphorus insecticides was diagnosed in Aedes aegypti (Linnaeus, 1762) from Santiago de Cuba in 1997 and some of them are still used up to date; hence the need of ascertaining how the insecticidal resistance has changed in recent times, particularly in 2009. OBJECTIVE: to evaluate the resistance to organophosporus insecticides in larvae from Santiago de Cuba collected in 2009, and its variation in comparison with that observed in 1997; and to determine the frequency of occurrence of resistance mechanisms on the basis of high esterase activity and its classification. METHODS: resistance to organophosphorus insecticides such as malathion, pirimiphos, methyl, phenitrotion, phention, temephos and clorpiriphos in larvae by using the WHO recommended methodology. The esterase mechanism was identified through biochemical assays and polyacrylamide gel electrophoresis. RESULTS: larvae from the Santiago de Cuba strain were susceptible to malathion, pirimiphos, methyl and phenitrothion; there was no variation with the results achieved in a Santiago de Cuba strain in 1997, moderate resistance to phenthion and high resistance to temephos and chlorpiriphos were observed. When comparing these results with those of 1997, it was noted that resistance to the three insecticides increased in the 1997-2009 period. In the Santiago de Cuba strain 2009, it was shown that esterase activity was very high at a rate of 0,7. The presence of an amplified type B esterase with relative mobility of 0.95 cm was detected, which did not exist in the reference strain. CONCLUSIONS: resistance to insecticides and its mechanisms are highly variable, even in the same species subjected to various intensities in the insecticidal use, therefore, it is necessary to constantly monitor both aspects at local level in the course of time, with a view to an effective vector control program.