Within-flock variations in strongyle worm infections in sheep: The need for adequate diagnostic samples

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Abstract
Extract The results of several recent studies have emphasized the pitfalls inherent in the use of faecal worm-egg counts for the quantitative diagnosis of strongyle worm infections in ruminants (Kingsbury, 1965 Kingsbury, P. A. 1965. Relationship between egg counts and worm burdens of young sheep. Vet. Rec., 77: 900–901. [Google Scholar] ; Gibson, 1965 Gibson, T. E. 1965. Examination of faeces for helminth eggs and larvae. Vet. Bull., 35: 403–410. [Google Scholar] ; Gordon, 1967 Gordon, H. McL. 1967. The diagnosis of helmin-thosis in sheep. Vet. med. Rev. No. 2/3, : 140–168. [Google Scholar] ; Rubin, 1967 Rubin, R. 1967. Some observations on the interpretations of faecal egg counts. Am. J. vet. Clin. Path., 1: 145–148. [Google Scholar] ; Michel, 1968 Michel, J. F. 1968. Faecal egg counts in infections of gastro-intestinal nematodes in cows. Vet. Rec., 82: 132–133. [Web of Science ®] [Google Scholar] ). However, in these studies, most consideration has been given to the various factors which affect the accuracy per se of the individual egg count. In the case of strongyle infections in sheep, little attention has been given to the within-flock variationsin level and relative generic cornposition of worm burdens which affect the interpretation and diagnostic validity of both faecal egg counts and worm counts, on a flock basis. While it is sometimes necessary to diagnose the presence or degree of parasitic infection in an individual animal, the flockis usually the unit concerned.