Changes in glutathione S-transferase activity in DDT resistant natural Mexican populations of Anopheles albimanus under different insecticide resistance management strategies

Biochemical assays on Anopheles albimanus collected for 3 years in southern Mexico villages after house spraying of a single insecticide [DDT or a pyrethroid (PYR)], a two insecticide mosaic [organophosphate (OP)/PYR] or a three insecticide annual rotation (OP-PYR-carbamate), defined the relative rates of selection of glutathione S-transferase-based resistance. After 3 years of rotation, mosaic and single PYR strategies, there was a decrease in the glutathione S-transferase (GST) activity, returning to susceptible levels, with few variations. In the rotation strategy, GST activity increased significantly in one group of villages, when OP treatment was replaced by the PYR in the 2nd treatment year. While, GST activity increased only in one village out of six continuously PYR-treated in the 1st year. In the DDT-treated villages, one group had increased activity in the 1st year, but this declined in years 2 and 3; GST activity of the other DDT-treated group were unchanged during the trial.