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A survey of Rhipicephalus microplus populations for mutations associated with pyrethroid resistance
Andrew C Chen1, Haiqi He, Kevin B Temeyer
1Knipling-Bushland U.S. Livestock Insects Research Laboratory, USDA-ARS, 2700 Fredericksburg Rd., Kerrville, TX 78028-9184, USA. andychen@tamu.edu
Abstract:
Mutations associated with pyrethroid resistance were found in Mexican strains of Rhipicephalus microplus (Canestrini). A mutation in the sodium channel gene was reported in strains highly resistant to permethrin and another mutation in an esterase gene in a strain that shows moderate resistance to the same pesticide. Methods based on the melting temperature difference of amplified allele-specific DNA fragments were developed that can detect these mutations rapidly in individual larvae. When these methods were applied to ticks from various strains of R. microplus from Australia, neither of these mutations could be demonstrated. Different resistance mechanisms have apparently developed independently between Australian and Mexican strains of R. microplus.
Insights
Pyrethroid resistance in Mexican Rhipicephalus microplus ticks is linked to specific gene mutations. Australian strains show different resistance mechanisms, indicating independent evolution in these cattle tick populations.
Area of Science:
- Veterinary Entomology
- Molecular Biology
- Pest Resistance
Background:
- Pyrethroid pesticides are crucial for controlling Rhipicephalus microplus (cattle ticks).
- Genetic mutations are increasingly identified as a primary driver of pesticide resistance in tick populations.
- Understanding these genetic variations is key to managing effective tick control strategies.
Purpose of the Study:
- To identify and characterize specific genetic mutations conferring pyrethroid resistance in Mexican Rhipicephalus microplus strains.
- To develop rapid molecular diagnostic tools for detecting these resistance-conferring mutations.
- To compare the genetic basis of pyrethroid resistance between Mexican and Australian Rhipicephalus microplus populations.
Main Methods:
- DNA amplification and allele-specific assays utilizing melting temperature differences.
- Screening of individual Rhipicephalus microplus larvae from diverse geographical origins.
- Sequencing of sodium channel and esterase genes to identify specific mutations.
Main Results:
- Mexican Rhipicephalus microplus strains exhibited mutations in sodium channel and esterase genes associated with high and moderate permethrin resistance, respectively.
- Developed molecular assays successfully detected these specific mutations in individual larvae.
- No evidence of these specific Mexican mutations was found in Australian Rhipicephalus microplus strains.
Conclusions:
- Distinct genetic mechanisms underlie pyrethroid resistance in Mexican and Australian Rhipicephalus microplus populations.
- The identified mutations and developed diagnostic tools are valuable for targeted resistance management in Mexico.
- Independent evolution of resistance mechanisms highlights the need for geographically tailored pest control strategies.
