Insecticide resistance

This video summarizes key updates to WHO's guidance for monitoring insecticide resistance in disease vectors, including guidance for Anopheles, Aedes and Culex, the new WHO bottle bioassay, the new standard operating procedures for conducting insecticide resistance monitoring bioassays and the newly established insecticides’ discriminating concentrations, the updated DHIS2 forms for collecting insecticide resistance data and the platform for monitoring biological threats (Malaria Threats Map).

This bioassay is a direct response-to-exposure test, measuring mosquito mortality 24 hours after exposure to a known standard concentration of an insecticide for a period of 1 hour. This SOP should be followed for testing mosquito susceptibility to insecticides that are suitable for impregnation of filter papers. For insecticides that are unstable on filter papers or that cannot be impregnated on filter papers, the WHO bottle bioassay procedure should be followed instead. 

Filter papers impregnated with standard discriminating concentrations of insecticides are needed for this test. The corresponding filter papers and test kits can be purchased from the Universiti Sains Malaysia (see procurement of test kits above).

The bottle bioassay should be used to evaluate vector susceptibility to insecticides that are unstable or cannot impregnate usual filter papers. This SOP is for testing susceptibility to these insecticides and should not be used for insecticide growth regulators that impact mosquito fecundity/ fertility. For insecticides that are suitable for impregnation of filter papers, the SOP for WHO tube tests should be followed.

The WHO bottle bioassay is a modified version of the United States CDC bottle bioassay and has been developed to harmonize the test end-points with those of the WHO tube test, so that mosquito mortality is evaluated at the same time point post-exposure. The WHO bottle bioassay is a direct response-to-exposure test, measuring mosquito mortality after 1 hour of exposure to a known standard concentration of an insecticide.