The persistence and fate of inhibited Haemonchus contortus larvae in young sheep

Authors: McKenna PB
Publication: New Zealand Veterinary Journal, Volume 22, Issue 7, pp 122-126, Jul 1974
Publisher: Taylor and Francis

Animal type: Livestock, Production animal, Ruminant, Sheep
Subject Terms: Alimentary system/gastroenterology, Parasites - internal, Nematode
Article class: Scientific Article

---

Abstract: Inhibited development of Haemonchus contortus at an early fourth larval stage has been reported frequently both in New Zealand (McKenna, 1973a; Brunsdon, 1973) and elsewhere (Muller, 1968; Connan, 1968, 1971; Blitz and Gibbs, 1972a, b; Ayalew and Gibbs, 1973) and although it is generally accepted that such larvae are capable of eventual resumption of development (Blitz and Gibbs, 1971a), relatively little is known regarding their persistence in sheep. Blitz and Gibbs (1972b) have demonstrated that inhibited larvae of this parasite are not transitory since such forms may be recovered from housed sheep at least 4 months after removal from pasture. Others (Gibbs, 1964; Wilson and Samsoa, 1970) have suggested that the maturation of inhibited larvae acquired in the autumn may be responsible for later outbreaks of “winter” haemonchosis and may also make a significant contribution to the post-parturient rise in faecal egg counts of lactating ewes in the spring (Field et al 1960; Proctor and Gibbs, 1968a, b). While this evidence suggests that some inhibited larvae of H. contortus may be long-lived, the authors do not, however, provide any information on either the numbers or the proportions of such forms which may persist in this state for any length of time. In view of the apparent epidemiological importance of this phenomenon, the present investigation was therefore undertaken to provide such data.

---