On some factors influencing the output of the larvae of Prostrongylids of sheep in natural infections.

Summary The output of first stage Protostrongvlid larvae of sheep was studied in natural infections. Three sets of observations were obtained from October 1977 to December 1978 in three regions. The larval output varied with the species harboured by sheep and with the density of worm populations. Anthelmintic treatments influenced the fecundity of worms. The age of the animals was an important cause of variation in the size of larval output; a rise of the latter was observed in pregnant ewes at the period of lambing. A seasonal variation in output was recorded. The fauna was characterized by the high prevalence of Muellerius and Neostrongylus.