Diagnosis of resistance alleles in codon 167 of the beta-tubulin (Cya-tbb-1) gene from third-stage larvae of horse cyathostomins.

The research conducted discusses the investigation into resistance alleles in a specific gene (Cya-tbb-1) of horse cyathostomins. Key findings included different rates of certain genotypes across three different locations and an unnamed mutation found in a significant percentage of samples.

Research Overview

This research was primarily focused on investigating resistance alleles in the third-stage larvae of horse cyathostomins, particularly at codon 167 of the beta-tubulin gene (Cya-tbb-1). The study sought to identify and compare rates of certain resistant genotypes and mutations across various locations.

• The beta-tubulin gene was targeted as it is the gene most commonly associated with resistance mutations. The specific focus was on codon 167 and any resistant genotypes present.
• 173 different larvae were included in this investigation, sourced from three different locations: Parana, Sao Paulo, and Santa Catarina.

Key Findings

Two key findings emerged from this research study:

• The presence of the heterozygous resistant genotype – TTC/TAC was found to vary across the different locations. Parana demonstrated the highest percentage with 61.2%, followed by Santa Catarina with 38.5% and Sao Paulo with 31.5%.
• An unnamed mutation at codon 172, which resulted in a serine (S) to threonine (T) substitution, was identified in 17.9% of samples from Parana and 13.0% of samples from Sao Paulo. This mutation had not previously been published in the literature.

Implications and Further Considerations

The report revealed significant variations in the presence of the resistant genotype across different geographical locations and identified a previously undisclosed mutation. The findings of the study could hold implications for the control of equine gastrointestinal nematodes, which encounter resistance challenges.

• The study’s findings were compared to fecal egg count data from the same locations, demonstrating a correlation (R=-0.79).
• The study suggests that the routine molecular diagnostic in individual larvae can help to determine population genetic distribution, effectively predicting and preparing for drug failure scenarios.