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Detection of pyrethroid resistance in Anopheles mosquitos
S M Magesa1, O Aina, C F Curtis
1National Institute for Medical Research, Amani Medical Research Centre, Tanga, United Republic of Tanzania.
Abstract:
Although pyrethroid insecticides are a promising means of controlling Anopheles malaria vectors, there is a need to monitor for resistance. It has been proposed that the results of the WHO-recommended testing method, involving exposure to impregnated paper for 1 hour, might be misleading because of knockdown during this period, and that exposure to a higher dose of pyrethroid for 2 minutes might be preferable. However, comparative tests with a susceptible and a permethrin-resistant strain of A. stephensi showed that exposure for 1 hour was at least as sensitive in detecting resistance as was the short exposure method.
Insights
Monitoring pyrethroid insecticide resistance in malaria vectors like Anopheles mosquitoes is crucial. The standard 1-hour WHO test is as effective as a shorter, higher-dose method for detecting resistance.
Area of Science:
- Medical Entomology
- Insecticide Resistance Management
- Public Health
Background:
- Pyrethroid insecticides are vital for controlling Anopheles mosquitoes, the primary vectors of malaria.
- Monitoring insecticide resistance in mosquito populations is essential for effective malaria control programs.
- Concerns exist that the standard WHO 1-hour pyrethroid exposure test may be influenced by mosquito knockdown.
Purpose of the Study:
- To compare the sensitivity of the WHO-recommended 1-hour pyrethroid exposure method with a shorter, higher-dose exposure method for detecting insecticide resistance in Anopheles mosquitoes.
Main Methods:
- Comparative testing of a susceptible and a permethrin-resistant strain of A. stephensi.
- Evaluation of the WHO-recommended 1-hour exposure method.
- Evaluation of a proposed 2-minute higher-dose pyrethroid exposure method.
Main Results:
- The 1-hour exposure method was found to be at least as sensitive in detecting permethrin resistance as the 2-minute exposure method.
- Knockdown observed during the 1-hour exposure did not appear to compromise the detection of resistance.
Conclusions:
- The standard 1-hour WHO pyrethroid susceptibility testing method is reliable for detecting insecticide resistance in Anopheles mosquitoes.
- The proposed shorter, higher-dose method does not offer superior sensitivity for detecting pyrethroid resistance compared to the current WHO standard.