title: Genetic basis of benzimidazole resistance inTeladorsagia circumcinctain Ireland.
abstract: Resistance to benzimidazole (BZ) anthelmintics is common in ovine nematodes of economic importance. Single nucleotide polymorphisms (SNP) at three positions in the isotype 1 β- tubulin gene have been associated with BZ resistance and molecular tests for the detection of BZ resistance have been developed. In order to determine if such tests are practicable in Ireland the polymorphisms associated with BZ resistance must be identified. To this end, BZ-resistant nematodes were recovered from four farms in Ireland. ResistantTeladorsagia circumcincta,Cooperia curticeiandTrichostrongylus colubriformiswere recovered, with resistantT. circumcinctathe most common and the only species studied further. Sequencing of the isotype 1 β-tubulin gene from resistantT. circumcinctaidentified a T - A transition, resulting in an F200Y substitution known to be responsible for BZ-resistance, on three of the farms. However, on the fourth farm the frequency of the resistant A allele was only 0.33 indicating another BZ resistance mechanism may be present on this farm. An additional polymorphism resulting in a substitution of glutamate for leucine (E198L) was also found on this farm at low frequency (0.17). No polymorphisms at position 167 were identified on any farm. Therefore, molecular tests to detect BZ resistance inT. circumcinctain Ireland could prove useful; however, they may result in some instances of resistance remaining undetected.
authors.affiliation: Animal and Bioscience Department, Teagasc, Grange, Dunsany, Co. Meath, Ireland.|School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Jason D
authors.initials: JD
authors.lastname: Keegan
authors.affiliation: Animal & Bioscience Dept, Teagasc, Mellows Campus, Athenry, Co. Galway, Ireland.
authors.forename: Barbara
authors.initials: B
authors.lastname: Good
authors.affiliation: School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Theo
authors.initials: T
authors.lastname: de Waal
authors.affiliation: Department of Agriculture Food and the Marine, Central Veterinary Research Laboratory, Backweston, Co. Kildare, Ireland.
authors.forename: June
authors.initials: J
authors.lastname: Fanning
authors.affiliation: Animal and Bioscience Department, Teagasc, Grange, Dunsany, Co. Meath, Ireland.
authors.forename: Orla M
authors.initials: OM
authors.lastname: Keane
keywords: Anthelmintic; Benzimidazole; Resistance; Sheep; Teladorsagia; β-tubulin