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Variation among faecal egg counts following natural nematode infection in Scottish Blackface lambs

Published online by Cambridge University Press:  06 October 2005

M. J. STEAR ,
O. ABUAGOB ,
M. BENOTHMAN ,
S. C. BISHOP ,
G. INNOCENT ,
A. KERR  and
S. MITCHELL
M. J. STEAR
Affiliation:
Glasgow University Veterinary School, Bearsden Road, Glasgow G61 1QH
O. ABUAGOB
Affiliation:
Glasgow University Veterinary School, Bearsden Road, Glasgow G61 1QH
M. BENOTHMAN
Affiliation:
Glasgow University Veterinary School, Bearsden Road, Glasgow G61 1QH
S. C. BISHOP
Affiliation:
Roslin Institute (Edinburgh), Roslin, Midlothian EH25 9PS
G. INNOCENT
Affiliation:
Glasgow University Veterinary School, Bearsden Road, Glasgow G61 1QH
A. KERR
Affiliation:
Glasgow University Veterinary School, Bearsden Road, Glasgow G61 1QH
S. MITCHELL
Affiliation:
Glasgow University Veterinary School, Bearsden Road, Glasgow G61 1QH
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Abstract

Faecal egg counts were examined in 2 flocks of naturally infected Scottish Blackface sheep in southern and central Scotland. The distribution of mean counts was right skewed and similar to a gamma distribution. The counts varied with month, with mean counts rising from May to July, then falling but rising again in October, although data within each year did not always show such a clear pattern. There was no significant difference in mean egg count between the 2 farms examined. The distribution of egg count variances was also right skewed and conformed to a gamma distribution. There was a strong relationship between the mean and the variance for each population, implying that variation among populations in variances largely mirrored variation in mean egg counts. Populations with high mean egg counts and variances did not necessarily have more adult nematodes but had a greater number of adult nematodes from species other than Teladorsagia circumcincta, particularly Cooperia spp., Trichostrongylus axei and Trichostrongylus vitrinus. The contribution of different parasite species to the egg count explains the relatively poor and inconsistent fit of the negative binomial distribution to faecal egg counts in lambs.

Keywords

sheepnematodeegg countsvariancenegative binomial
Type
Research Article
Information
Parasitology , Volume 132 , Issue 2 , February 2006 , pp. 275 - 280
Copyright
2005 Cambridge University Press

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