The distribution of the pathogenic nematode Nematodirus battus in lambs is zero-inflated
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The distribution of the pathogenic nematode Nematodirus battus in lambs is zero-inflated. / Denwood, Matthew; Stear, M J; Matthews, L; Reid, S W J; Toft, Nils; Innocent, G T.
I: Parasitology, Bind 135, Nr. 10, 2008, s. 1225-35.Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
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TY - JOUR
T1 - The distribution of the pathogenic nematode Nematodirus battus in lambs is zero-inflated
AU - Denwood, Matthew
AU - Stear, M J
AU - Matthews, L
AU - Reid, S W J
AU - Toft, Nils
AU - Innocent, G T
PY - 2008
Y1 - 2008
N2 - 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.
AB - 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.
KW - Animals
KW - Bayes Theorem
KW - Female
KW - Male
KW - Markov Chains
KW - Monte Carlo Method
KW - Nematode Infections
KW - Parasite Egg Count
KW - Scotland
KW - Sheep
KW - Sheep Diseases
U2 - 10.1017/S0031182008004708
DO - 10.1017/S0031182008004708
M3 - Journal article
C2 - 18620622
VL - 135
SP - 1225
EP - 1235
JO - Parasitology
JF - Parasitology
SN - 0031-1820
IS - 10
ER -
ID: 137015573