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Assessment of ivermectin efficacy against gastrointestinal nematodes in cattle on four Scottish farms
  1. C. L. McArthur, BSc1,
  2. D. J. Bartley, BSc, PhD1,
  3. D. J. Shaw, BSc, PhD2 and
  4. J. B. Matthews, BVMS, PhD, MRCVS1
  1. Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Midlothian EH26 0PZ, UK
  2. Royal (Dick) School of Veterinary Studies and Roslin Institute, University of Edinburgh, Midlothian EH25 9RG, UK
  1. E-mail for correspondence claire.mcarthur{at}

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CURRENT control strategies targeted against gastrointestinal nematode infections in cattle rely heavily on the use of anthelmintics. Three drug classes are licensed for this purpose in the UK: benzimidazoles, imidazothiazoles and macrocyclic lactones (ML). The latter, in particular, ivermectin (IVM), is used extensively primarily because of its high efficacy and wide safety indices (González Canga and others 2009). Anthelmintic resistance (AR) has been reported widely in nematodes of small ruminants, but there have been fewer reports in cattle. The reason for this may be due to a true lower incidence of AR, because cattle are generally ‘drenched’ less frequently than sheep. It may also be due to the fact that infections caused by Cooperia oncophora, for which AR has been most commonly recorded in cattle, may not be detected because of the relatively low pathogenicity of this nematode in cattle. However, recently, there has been an increase in reports of AR in cattle, especially in the southern hemisphere (Sutherland and Leathwick 2011). Single populations have been identified that are resistant to multiple anthelmintic classes (Waghorn 2006).

The first UK case of IVM resistance in cattle nematodes was found in 1999 (Stafford and Coles 1999), and other reports have been published subsequently (Sargison and others 2009, Orpin 2010). Apart from these studies, little research has been undertaken on the regional prevalence of AR in cattle nematodes in the UK. A questionnaire study of helminth management practices on Scottish cattle farms is underway at the Moredun Research Institute. As part of this, farmers have been asked to participate in a faecal egg count reduction test (FECRT) to assess the efficacy of IVM on …

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