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The diagnostic value and interpretation of faecal egg counts in sheep
Authors: McKenna PBPublication: New Zealand Veterinary Journal, Volume 29, Issue 8, pp 129-132, Aug 1981
Publisher: Taylor and Francis
Animal type: Livestock, Production animal, Ruminant, Sheep
Subject Terms: Abdomen, Alimentary system/gastroenterology, Diagnostic procedures, Nematode, Parasites - internal
Article class: Scientific Article
Abstract: The relationship between the strongyle egg count and (a) the total strongyle worm burden and (b) the total pathogenic index (T.P.I.) of the worm burden in 190 young (up to 12 months of age) and 131 old (over 12 months of age) sheep was examined. In young sheep, mean egg counts were found to provide a useful indicator of the seasonal changes in the level of infection (r = 0.99) while a correlation coefficient of 0.74 between individual egg and worm counts (Nematodirus excluded) was recorded. In old sheep the corresponding correlation coefficients were 0.16 and 0.23, respectively. When egg and worm counts were categorised according to the concept of low, moderate and high, however, the association between them was found to be almost equally consistent in both age classes of stock. Consideration of these findings and the fact that the association between the egg count and the T.P.I. was, in individual young sheep, almost as good as (r = 0.69), and in old sheep, notably better (r = 0.69) than, that between the corresponding egg and worm counts, suggests that faecal egg counts are of considerable diagnostic value. In the case of Nematodirus infections, however, where the correlation coefficient between egg and worm counts in young sheep was 0.35 and where much of the damage to the host may occur before egg laying has commenced, only very limited reliance should be placed on egg counts for diagnostic purposes.
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