The detection of resistance to ivermectin by the faecal egg count reduction test

Authors: McKenna PB
Publication: New Zealand Veterinary Journal, Volume 38, Issue 4, pp 169-170, Dec 1990
Publisher: Taylor and Francis

Animal type: Livestock
Subject Terms: Alimentary system/gastroenterology, Animal remedies/veterinary medicines, Anthelmintics, Parasite control, Parasites - internal, Treatment/therapy, Nematode
Article class: Correspondence

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Abstract: Anthelmintic resistance in gastrointestinal nematode parasites of sheep and goats is usually detected in the field by means of the faecal egg count reduction (FECR) test. However, a recent publication in this journal has raised some doubts regarding the appropriateness of this procedure for detecting resistance to ivermectin by suggesting that treatment with this drug may affect the fecundity of surviving worms. Little evidence was provided to support this suggestion by, for example, counting eggs in uteri and, in my opinion, such concerns are neither justified by the results of this study, nor warranted by the weight of other existing evidence. Over the last few years, field and laboratory selected strains of parasitic nematodes showing resistance to ivermectin have been recorded in sheep and goats on several occasions…

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