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A mechanistic model of developing immunity to Teladorsagia circumcincta infection in lambs

Published online by Cambridge University Press:  15 October 2010

D. R. SINGLETON ,
M. J. STEAR  and
L. MATTHEWS
D. R. SINGLETON*
Affiliation:
The Boyd Orr Centre for Population and Ecosystem Health, Institute of Comparative Medicine, Faculty of Veterinary Medicine, University of Glasgow, Bearsden Road, Glasgow G61 1QH, Scotland
M. J. STEAR
Affiliation:
The Boyd Orr Centre for Population and Ecosystem Health, Institute of Comparative Medicine, Faculty of Veterinary Medicine, University of Glasgow, Bearsden Road, Glasgow G61 1QH, Scotland
L. MATTHEWS
Affiliation:
The Boyd Orr Centre for Population and Ecosystem Health, Institute of Comparative Medicine, Faculty of Veterinary Medicine, University of Glasgow, Bearsden Road, Glasgow G61 1QH, Scotland
*
*Corresponding author: E-mail: [email protected]
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Summary

Acquired immunity influences the severity of parasitic disease, but modelling the effects of acquired immunity in helminth infections has proved challenging. This may be due to a lack of suitable immunological data, or to the perceived complexity of modelling the immune response. We have developed a model of T. circumcincta infection in domestic sheep that incorporates the effects of acquired immunity on parasite establishment and fecundity. A large data set from commercially managed populations of Scottish Blackface sheep was used, which included relationships between IgA activity and worm length, and between worm length and fecundity. Use was also made of a recently published meta-analysis of parasite establishment rates. This realistic but simple model of nematode infection emulates observed patterns of faecal egg counts. The end-of-season faecal egg counts are remarkably robust to perturbations in the majority of the parameters, possibly because of priming of the immune system early in the season, reducing parasite establishment and growth and, therefore, faecal egg counts. Lowering the amount of early infection leads to higher end-of-season egg counts. The periparturient rise in egg counts in ewes appears to have an important role in supplying infection for the priming of the immune response. This feedback in the immune priming suggests that nematode infections may be difficult to eliminate.

Keywords

Teladorsagia circumcinctasheepnematodeacquired immunityestablishmentfecundityfaecal egg countIgA
Type
Research Article
Information
Parasitology , Volume 138 , Issue 3 , March 2011 , pp. 322 - 332
Copyright
Copyright © Cambridge University Press 2010

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