Control of Nematodirus spp. infection by sheep flock owners in Northern Ireland

Connor McMahon, Hillary W.J. Edgar, Jason P. Barley, Robert E.B. Hanna, Gerard P. Brennan, Ian Fairweather*

*Corresponding author for this work

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1 Citation (Scopus)
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To address a lack of information on the control of ovine helminth parasites in Northern Ireland (NI), a number of research projects have been undertaken, dealing with gastrointestinal nematodes, tapeworms and liver fluke. This investigation concerns Nematodirus and concentrates on three aspects of disease: farm management strategies for its control, derived from the results of a Questionnaire; the efficacy of treatment used by farmers, as determined by a coprological survey; and the hatching requirements of Nematodirus eggs, that is, whether prolonged chilling is a pre-requisite for hatching.

A Questionnaire was sent to 252 sheep farmers in NI in March 2012 (covering the years 2009–2012) and replies were received from 228 farmers. Under-dosing, inaccurate calibration of equipment and inappropriate productchoice were poor practices identified. Following this survey, the efficacy of treatment of Nematodirus spp. in sheep flocks was evaluated in April and May 2012. Sampling kits were sent to 51 flock owners, all of whom returned pre- andpost-anthelmintic dosing faecal samples to the laboratory for analysis. At the time of treatment, 41 flocks were positive for Nematodirus (as diagnosed by the presence of eggs). Reduced benzimidazole efficacy was detected in 35.7% offlocks tested (n = 28). Although only involving a small number of flocks, reduced efficacy of levamisole treatment was detected in 50%, of avermectins in 33% and of moxidectin in 75% of flocks tested (n = 2, 6 and 4, respectively). In the egg hatch experiment, carried out under “chilled” and “non-chilled” conditions, 43% of the eggs in the “non-chilled”group were able to hatch, compared to 100% in the “chilled” group.

The identification of inefficient control strategies argues for continued education of stockholders, in order to improve their management programmes. This is particularly important where the practices might impact on the development of anthelmintic resistance, which has been shown to exist on NI farms. The appropriate choice of anthelmintic is a vital part of this plan. The ability of eggs to hatch under non-chilled conditions demonstrates a flexibility in hatching behaviour. This may represent an adaptation to climate change and account for the recent emergence of a second, autumnal peak of infection
Original languageEnglish
Article number31
Pages (from-to)1-11
JournalIrish Veterinary Journal
Issue number31
Publication statusPublished - 19 Oct 2017


  • Egg hatch behaviour
  • Faecal egg count reduction test
  • Nematodirus spp.
  • Northern Ireland
  • Questionnaire
  • Survey

ASJC Scopus subject areas

  • veterinary(all)


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