title: A nationwide survey of anthelmintic treatment failure on sheep farms in Ireland.
abstract: BACKGROUND
  Between 2013 and 2015 the Department of Agriculture, Food and the Marine (DAFM) administered a sheep technology adoption programme (STAP), with the aim of increasing profitability on Irish sheep farms by encouraging the adoption of best management practices. One of the options available to STAP participants was to test the efficacy of the anthelmintic treatment (benzimadazole, levamisole or macrocyclic lactone) used in their flocks by means of a drench test, which is a modification of the faecal egg count reduction test; individual faecal samples were collected from the same group of lambs before and after anthelmintic treatment, the number of eggs present pre and post treatment was subsequently determined from a pooled sample.
  
  
  RESULTS
  In total, 4211 drench tests were undertaken by farmers during the 3 years of the programme. Information on the anthelmintic product used was available for 3771 of these tests; anthelmintics from the classes benzimidazole (BZ), levamisole (LV) and macrocyclic lactone (ML) (avermectins (AVM) plus moxidectin (MOX)) were used in 42.0%, 23.4% and 32.5% of tests, respectively. The remaining 2.1% of tests involved an inappropriate product. The efficacy of treatment against 'other trichostrongyles' (excludingNematodirusspp andStrongyloides papillosus.) could be established for 1446 tests, and 51% of these tests were considered effective (i.e. a reduction of faecal egg count (FEC) ≥ 95%). There was a significant difference among the drug groups in efficacy; 31.5%, 51.9%, 62.5% and 84% of treatments were considered effective for BZ, LV, AVM, MOX, respectively. The efficacy of treatment againstNematodirusspp. could be established for 338 tests and the overall efficacy was 96%.
  
  
  CONCLUSIONS
  Due to the significant difference among the anthelmintic classes for efficacy against 'other trichostrongyles' along with the high level of efficacy againstNematodirusspp., a genus for which anthelmintic resistance is rarely reported, it is concluded that anthelmintic resistance was responsible for the majority of the anthelmintic treatment failures observed.
authors.affiliation: Animal & Bioscience Department, Teagasc Grange, Dunsany, Co., Meath, Ireland.|Department of Agriculture, Food and the Marine, Central Veterinary Research Laboratory, Backweston, Co., Kildare, 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 Department, Teagasc Grange, Dunsany, Co., Meath, Ireland.
authors.forename: Orla M
authors.initials: OM
authors.lastname: Keane
authors.affiliation: Animal & Grassland Research & Innovation Centre, Teagasc, Athenry, Co., Galway, Ireland.
authors.forename: Barbara
authors.identifier: 0000-0002-1314-6805
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: Kilkenny Regional Veterinary Laboratory, Hebron Road, Kilkenny, Co., Kilkenny, Ireland.
authors.forename: Marian
authors.initials: M
authors.lastname: Denny
authors.affiliation: Animal & Grassland Research & Innovation Centre, Teagasc, Athenry, Co., Galway, Ireland.
authors.forename: James P
authors.initials: JP
authors.lastname: Hanrahan
authors.affiliation: Limerick Regional Veterinary Laboratory, Knockalisheen, Co., Limerick, Ireland.
authors.forename: William
authors.initials: W
authors.lastname: Fitzgerald
authors.affiliation: Kilkenny Regional Veterinary Laboratory, Hebron Road, Kilkenny, Co., Kilkenny, Ireland.
authors.forename: Maresa
authors.initials: M
authors.lastname: Sheehan