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

Publication date: Available online 6 October 2019Source: International Journal for Parasitology: Drugs and Drug ResistanceAuthor(s): Frank Turnbull, Eileen Devaney, Alison A. Morrison, Roz Laing, Dave J. BartleyAbstractRecent 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 monepantel). 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...
Source: International Journal for Parasitology: Drugs and Drug Resistance - Category: Parasitology Source Type: research