The seasonal occurrence of inhibited abomasal nematodes in young sheep

Authors: McKenna PB
Publication: New Zealand Veterinary Journal, Volume 22, Issue 11, pp 214-217, Nov 1974
Publisher: Taylor and Francis

Animal type: Sheep
Subject Terms: Alimentary system/gastroenterology, Environment, Epidemiology, Parasites - internal, Nematode, Seasonality/photoperiod
Article class: Scientific Article

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Abstract: 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 Sotmmmerville, 1969). Of the abomasal parasites of sheep, inhibition in Haemonthus contortus and Ostertagia circumcincta occurs at the early fourth stage (Blitz and Gibbs, 1971; Sommerville, 1953, 1954) and in Trichostrongylus axei at a more loosely defined “fourth” larval stage (Reid and Armour, 1972). The precise, cause of this phenomenon is, as yet, unknown but it has been shown to have a seasonal nature forming an integral part of the regular pattern of infection (Muller, 1968; Connan, 1971; Blitz and Gibbs, 1972a, b; James and Johnstone, 1967a, b; Reid and Armour, 1972) and to have important implications in the transmission of these nematodes (Field et al 1960; Procter and Gibbs, 1968a, b). In New Zealand the epidemiological significance of this phenomenon in sheep has been largely overlooked. Although recent studies (McKenna, 1973; Brunsdoa. 1973) have gone some way to correcting this omission, these have been of short duration and have provided little information concerning the seasonal occurrexe of inhibited sheep abomasal nematodes during the entire year. The present investigation was therefore undertaken to provide these data.

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