Field evaluation of methods for estimating carbamate resistance in Anopheles albimanus mosquitos from a microplate assay for insensitive acetylcholinesterase.

The reliability of a published method to predict survivorship in the WHO propoxur-resistance bioassay (WHO test) from the results of a biochemical assay for detecting the insensitivity of acetylcholinesterase (AChE) is described. For biochemical assay data from three field populations of Anopheles albimanus mosquitos, the results obtained using the method did not correlate consistently with the findings of the WHO test. A modified method is then described that eliminates the effect on the assay of factors unrelated to pesticide resistance, and it is shown that this modification can be used to predict survivorship in the WHO test for mosquitos from three study sites in Guatemala. The results show that when scored visually, the insensitive AChE microplate assay is an accurate method of estimating survival in the WHO test, regardless of whether the mosquitos tested are blood-fed or not. Recommendations are given for the application and analysis of data from the insensitive AChE microplate assay for detecting and monitoring resistance to carbamate insecticides.