A note on estimating selection pressures on insecticide-resistance genes

Area of Science:

• Entomology
• Population Genetics
• Molecular Biology

Background:

• Insect vectors transmit diseases, and resistance genes pose a significant challenge to control efforts.
• Understanding selection pressures on resistance genes is vital for predicting their spread and developing effective management strategies.
• Existing methods for estimating selection coefficients can be limited, necessitating refined approaches.

Purpose of the Study:

• To describe and apply methods for estimating selection coefficients of resistance genes in insect vectors.
• To evaluate the relative fitness of susceptible versus resistant insect populations under insecticide selection.
• To highlight the importance of gene dominance in selection estimations for resistance management.

Main Methods:

• Estimating selection coefficients using post-selection phenotype frequencies across multiple generations.
• Calculating relative fitness (1-s) of susceptible insects compared to resistant ones.
• Analyzing deviations from Hardy-Weinberg expectations to infer selection pressures.

Main Results:

• Relative fitness of susceptible Anopheles labranchiae to DDT was estimated at 31-38%.
• Relative fitness of susceptible Anopheles funestris to dieldrin was estimated at 40%.
• Population mixing can confound selection estimations, as observed in Anopheles gambiae.

Conclusions:

• Accurate estimation of selection pressures is essential for predicting and managing insecticide resistance in disease vectors.
• The effective dominance of resistance genes in natural populations is a critical factor for successful resistance control.
• Developed methods and computer programs can aid in estimating selection coefficients and informing resistance management strategies.