The diagnostic value and interpretation of faecal egg counts in sheep

Publisher Website
Google Scholar
Abstract
The relationship between the strongyle egg count and the total strongyle worm burden and the total pathogenic index (TPI) of the worm burden in 190 young (up to 12 mo. of age) and 131 old (> 12 mo. of age) sheep was examined. In young sheep, mean egg counts provided a useful indicator of the seasonal changes in the level of infection (r = 0.99) while a r of 0.74 between individual egg and worm counts (Nematodirus excluded) was recorded. In old sheep the corresponding r were 0.16 and 0.23, respectively. When egg and worm counts were categorized according to the concept of low, moderate and high the association between them was 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 TPI 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 fecal egg counts are of considerable diagnostic value. In the case of Nematodirus infections where the r 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.