Monepantel resistant Trichostrongylus colubriformis in goats in Brazil

Cintra, Maria Christine Rizzon; Teixeira, Valéria Natascha; Nascimento, Lígia Valéria; Ollhoff, Rüdiger Daniel; Sotomaior, Cristina Santos

doi:10.1016/j.vprsr.2017.11.005

Cited by 3 publications

(1 citation statement)

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“…The first cases of resistance were highlighted in field isolates of T. circumcincta and Trichostrongylus colubriformis in New Zealand flocks of sheep and goats (Leathwick et al, 2013; Scott et al, 2013). Resistance to MPTL has since also been reported in Haemonchus contortus from sheep in Uruguay (Mederos et al, 2014), the Netherlands (Van den Brom et al, 2015), Australia (Sales and Love, 2016) and Brazil (Martins et al, 2017; Ramos et al, 2018), in T. colubriformis in Brazilian sheep and goat flocks (Cintra et al, 2016, 2018) and in Trichostrongylus vitrinus , T. circumcincta and Oesophagostomum venulosum from a UK flock (Hamer et al, 2018; Bartley et al, 2019).…”

Section: Introductionmentioning

confidence: 90%

Genotypic characterisation of monepantel resistance in historical and newly derived field strains of Teladorsagia circumcincta

Turnbull

Devaney

Morrison

et al. 2019

International Journal for Parasitology: Drugs and Drug Resistan

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Recent reports of monepantel (MPTL) resistance in UK field isolates of Teladorsagia circumcincta has highlighted the need for a better understanding of the mechanism of MPTL-resistance in order to preserve its anthelmintic efficacy in this economically important species.Nine discrete populations of T. circumcincta were genotypically characterised; three MPTL-susceptible isolates, three experimentally selected MPTL-resistant strains and three field derived populations. Full-length Tci-mptl-1 gene sequences were generated and comparisons between the MPTL-susceptible isolates, MPTL-resistant strains and one field isolate, showed that different putative MPTL-resistance conferring mutations were present in different resistant isolates. Truncated forms of the Tci-mptl-1 gene were also observed. The genetic variability of individual larvae, within and between populations, was examined using microsatellite analyses at 10 ‘neutral’ loci (presumed to be unaffected by MPTL). Results confirmed that there was little background genetic variation between the populations, global FST <0.038. Polymorphisms present in exons 7 and 8 of Tci-mptl-1 enabled genotyping of individual larvae. A reduction in the number of genotypes was observed in all MPTL-resistant strains compared to the MPTL-susceptible strains that they were derived from, suggesting there was purifying selection at Tci-mptl-1 as a result of MPTL-treatment. The potential link between benzimidazole (BZ)-resistance and MPTL-resistance was examined by screening individual larvae for the presence of three SNPs associated with BZ-resistance in the β-tubulin isotype-1 gene. The majority of larvae were BZ-susceptible homozygotes at positions 167 and 198. Increased heterozygosity at position 200 was observed in the MPTL-resistant strains compared to their respective MPTL-susceptible population. There was no decrease in the occurrence of BZ-resistant genotypes in larvae from each population.These differences, in light of the purifying selection at this locus in all MPTL-resistant isolates, suggests that Tci-mptl-1 confers MPTL-resistance in T. circumcincta, as in Haemonchus contortus, but that different mutations in Tci-mptl-1 can confer resistance in different populations.

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