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Pyrethroid resistance in an Anopheles funestus population from Uganda
John C Morgan1, Helen Irving, Loyce M Okedi
1Liverpool School of Tropical Medicine, Liverpool, United Kingdom.
Plos One
|August 6, 2010
Summary
Anopheles funestus mosquitoes in Uganda show resistance to pyrethroids and DDT, a significant finding for malaria vector control. Metabolic resistance mechanisms, including elevated P450s, are implicated, highlighting the need for updated control strategies.
Area of Science:
- Medical Entomology
- Molecular Biology
- Insecticide Resistance
Background:
- Insecticide resistance in the malaria vector Anopheles funestus is poorly understood across Africa.
- Rearing field-caught Anopheles funestus mosquitoes has been a significant challenge.
Purpose of the Study:
- To determine the insecticide susceptibility status of Anopheles funestus in Uganda.
- To preliminarily characterize the resistance mechanisms in this mosquito population.
Main Methods:
- A novel forced egg-laying technique was employed to increase the yield of field-caught Anopheles funestus.
- WHO susceptibility bioassays were conducted for various insecticide classes.
- Sequencing of the sodium channel gene and biochemical assays (GSTs, P450s, pNPA) were performed.
- RT-PCR was used to confirm gene expression levels, specifically for CYP6P9b.
Main Results:
- Anopheles funestus in Tororo, Uganda, exhibited resistance to pyrethroids (permethrin, deltamethrin) and DDT.
- The population remained fully susceptible to bendiocarb, malathion, and dieldrin.
- No L1014F kdr mutation was detected, but other mutations may be involved in knockdown resistance.
- Elevated levels of GSTs, P450s, and pNPA suggest metabolic resistance, with a 12-fold overexpression of CYP6P9b confirmed by RT-PCR.
Conclusions:
- This study reports the first instance of pyrethroid/DDT resistance in Anopheles funestus in East Africa.
- The findings suggest widespread insecticide resistance in Anopheles funestus across Africa.
- Resistance in Anopheles funestus necessitates re-evaluation and adaptation of vector control programs.
