Genotypic evidence of benzimidazole resistance and population structure insights in zoonotic Trichostrongylus colubriformis from Thailand.

Abstract

Trichostrongylus is a genus of zoonotic gastrointestinal nematode which is part of the strongylid group, where close contact with livestock is a risk factor for human infection. High levels of benzimidazole-resistant Trichostrongylus populations have been reported in Thailand, where the resistant allele frequency of Trichostrongylus populations were consistently higher than the resistant allele frequency of Haemonchus. Despite its zoonotic importance and the widespread use of benzimidazoles for gastrointestinal nematode infections in livestock, Trichostrongylus is often overshadowed by the more pathogenic Haemonchus. Here, we aim to assess the benzimidazole resistance status of Trichostrongylus colubriformis adults in Thailand, and investigate their genetic diversity and population structure. Using 60 T. colubriformis adults from Sukhothai and Satun, benzimidazole resistance was genotypically detected using the b-tubulin gene. Genetic diversity was investigated by amplification of the mitochondrial COI gene of representative specimens. Significant levels of benzimidazole resistance was detected, with the heterozygous (RS) genotype as the majority (81.7%). The population genetic structure revealed high genetic diversity of T. colubriformis populations and high genetic differentiation between the populations from Thailand and other countries, indicative of limited genetic exchange between populations. Despite significant levels of benzimidazole resistance in Thailand's T. colubriformis population, the population structure, where limited genetic exchange and high genetic differentiation was observed between populations, suggests that locally targeted measures could be effective to curb anthelminthic resistance spread. However, additionally surveillance of this zoonotic nematode is advocated to sustainably safeguard animal and human health.