Modifications of pyrethroid effects associated with kdr mutation in Anopheles gambiae

Area of Science:

• Entomology
• Medical Entomology
• Insecticide Resistance

Background:

• Pyrethroid insecticides are crucial for malaria vector control, primarily through insecticide-treated nets.
• Emergence of pyrethroid resistance in Anopheles gambiae, driven by knockdown resistance (kdr) mutations, threatens malaria control efficacy.

Purpose of the Study:

• To investigate the impact of knockdown resistance (kdr) on pyrethroid efficacy in Anopheles gambiae.
• To compare the effectiveness of permethrin and deltamethrin against susceptible and resistant mosquito strains.

Main Methods:

• Topical application tests and exposure to permethrin-impregnated papers to determine knockdown times (KdT) and resistance ratios.
• Laboratory tunnel tests using pyrethroid-treated netting to assess mosquito behavior (passage, blood-feeding) and mortality.
• Experimental hut trials evaluating the efficacy of permethrin- and deltamethrin-treated bednets against Anopheles gambiae.

Main Results:

• Kdr conferred significant pyrethroid resistance, with reduced knockdown and increased survival rates in resistant strains.
• Permethrin and deltamethrin showed reduced efficacy against kdr-resistant Anopheles gambiae, particularly in tunnel tests and experimental huts.
• While pyrethroids still caused significant mortality in resistant populations, reduced irritancy and increased blood-feeding were observed compared to susceptible strains.

Conclusions:

• Knockdown resistance significantly compromises the effectiveness of pyrethroids in Anopheles gambiae, posing a challenge for malaria vector control.
• Monitoring kdr frequency and evaluating alternative or combination strategies are essential for sustainable malaria vector control.