The distribution of the pathogenic nematode Nematodirus battus in lambs is zero-inflated

Denwood, M.J., Stear, M.J., Matthews, L. , Reid, S.W.J., Toft, N. and Innocent, G.T. (2008) The distribution of the pathogenic nematode Nematodirus battus in lambs is zero-inflated. Parasitology, 135(10), pp. 1225-1235. (doi:10.1017/S0031182008004708)

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Abstract

Understanding the frequency distribution of parasites and parasite stages among hosts is essential for efficient experimental design and statistical analysis, and is also required for the development of Sustainable methods of controlling infection. Nematodirus battus is one of the most important organisms that infect sheep but the distribution of parasites among hosts is unknown. An initial analysis indicated a high frequency of animals without N. battus and with zero egg counts, suggesting the possibility of a zero-inflated distribution. We developed a Bayesian analysis using Markov chain Monte Carlo methods to estimate the parameters of the zero-inflated negative binomial distribution. The analysis of 3000 simulated data sets indicated that this method out-performed the maximum likelihood procedure. Application of this technique to faecal egg counts from lambs in a commercial upland flock indicated that N. battus counts were indeed zero-inflated. Estimating the extent of zero-inflation is important for effective statistical analysis and for the accurate identification of genetically resistant animals.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Innocent, Dr Giles and Denwood, Dr Matthew and Stear, Professor Michael and Matthews, Professor Louise and Reid, Professor Stuart
Authors: Denwood, M.J., Stear, M.J., Matthews, L., Reid, S.W.J., Toft, N., and Innocent, G.T.
College/School:College of Medical Veterinary and Life Sciences > Institute of Biodiversity Animal Health and Comparative Medicine
College of Medical Veterinary and Life Sciences > Institute of Infection Immunity and Inflammation
College of Medical Veterinary and Life Sciences > School of Veterinary Medicine
Journal Name:Parasitology
ISSN:0031-1820
ISSN (Online):1469-8161
Published Online:14 July 2008

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