The seasonal occurrence of inhibited abomasal nematodes in young sheep

Abstract

Extract

The susceptibility of many trichostrongylid nematodes, particularly those inhabiting the abomasa of domestic ruminants, to inhibited parasitic develolpment is well known. In most cases development is arrested at a precise point for a given species, usually occurring shortly before or after a moult (Rogers and Sommerville, 1969). Of the abomasal parasites of sheep, inhibition in Haemonchus contortus and Ostertagia circumcincta occurs at the early fourth stage (Blitz and Gibbs, 1971; Sommerville, 1953, 1954) and in Trichostrongvlus axei at a more loosely defined “fourth” larval stage (Reid and Armour, 1972).