Faecal egg counts are representative of digestive-tract strongyle worm burdens in sheep and goats.

The relationship between faecal egg counts and worm burdens in sheep and goats was studied in a large array of environments, from temperate (ewes, lambs or dairy-goats in France) or steppic (ewes in Middle-Atlas of Morocco) to Sahelian (young sheep and goats of Mauritania in West Africa) climates. The studied temperate worm communities were dominated by Teladorsagia and Trichostrongylus sp., and those from steppic areas by Teladorsagia, Marshallagia and Trichostrongylus sp.; Haemonchus contortus was highly predominant in the Sahelian regions. The fertility of worms depended on density (10 to 50% of variance) and presence of H. contortus to a lesser extent. For sheep and goats from several temperate and steppic areas, a good relationship between egg counts and worm burdens was established (r = 0.62). It was ameliorated when the percentage of H. contortus, the most prolific species was incorporated in the model. The predictive value of faecal egg count for assessing worm burden was only of interest for groups of hosts.