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Field studies on inhibition of Haemonchus contortus in sheep

Published online by Cambridge University Press:  06 April 2009

P. J. Waller  and
R. J. Thomas
P. J. Waller
Affiliation:
School of Agriculture, The University, Newcastle upon Tyne
R. J. Thomas
Affiliation:
School of Agriculture, The University, Newcastle upon Tyne
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Extract

The epidemiology of Haemonchus contortus was studied in north east England in lambs reared under field conditions with infected ewes. The parasite population was monitored by pasture larval counts, faecal egg counts and lamb postmortems. From 25 June to 11 November, eight lambs were slaughtered each month, together with eight worm-free tracer lambs. Postmortem worm counts showed that on 25 June, small numbers of adult H. contortus were present but no inhibited larvae. However, subsequently the number of worms recovered rose rapidly to 1000–5000 and the percentage inhibition increased to 57% in July, 75% in August and virtually 100% in September, October and November. On each sampling occasion no significant differences in worm count or percentage inhibition were recorded between experimental and tracer lambs. These results suggest that neither autumn climatic effects nor host immunity were responsible for inhibition in this strain of H. contortus.

Type
Research Article
Information
Parasitology , Volume 71 , Issue 2 , October 1975 , pp. 285 - 291
Copyright
Copyright © Cambridge University Press 1975

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