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Anthelmintic efficacy on sheep farms in south-west England
  1. M. Glover, BA, VetMB, CertSHP, MRCVS,
  2. C. Clarke, BVetMed, MRCVS,
  3. L. Nabb, BVMS, MRCVS and
  4. J. Schmidt, BVSc, MRCVS
  1. Torch Farm & Equine Ltd, Horsepond Meadow, South Molton, Devon EX36 4EJ, UK
  1. E-mail for correspondence: mikeglover{at}

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SHEEP production remains dependent upon the use of effective broad-spectrum anthelmintics to control the production limiting effects of gastrointestinal nematodes (GINs) and negative health and welfare impacts associated with parasitic gastroenteritis (PGE).

All major sheep-producing countries have reported resistance to the three ‘older’ groups of broad-spectrum anthelmintics; the 1-BZ, 2-LV and 3-ML groups (Kaplan and Vidyashankar 2012, Rose and others 2015). Of concern are recent reports of the rapid development of multigeneric resistance to monepantel, a novel anthelmintic of the 4-AD group (Scott and others 2013, Mederos and others 2014, Van den Brom and others 2015).

Anthelmintic resistance (AR), the heritable ability of GINs to tolerate a normally effective dose of an anthelmintic (Abbott and others 2013), has been responsible for outright failure of anthelmintics to control PGE (Sargison and others 2005, Wilson and Sargison 2007, Scott and others 2013, Mederos and others 2014, Van den Brom and others 2015). When involving multiple anthelmintic groups, resistance has reportedly led to the closure of flocks in the UK (Sargison and others 2005, Blake and Coles 2007). Suboptimal production, a consequence of early AR, has often remained unrecognised in flocks until laboratory-based or faecal egg count reduction tests (FECRTs) have revealed a lack of anthelmintic efficacy.

Surveys in the UK have revealed an upward trend over time in the proportion of flocks with AR (Cawthorne and Cheong 1984, Hong and others 1992, 1996, Bartley and others 2003, Taylor and others 2009, Mitchell and others 2010, Jones and others 2012, Stubbings 2012, Thomas and others 2015).

Results of a survey of faecal egg count reduction efficacy (FECR%) of …

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  • Disclaimer The study sponsors played no part in the study design, collection, analysis and interpretation of the data; in the writing of the report; and in the decision to submit the paper for publication.

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