LAUSR

Abstract To address the problem of prevalence of gastrointestinal parasite infections faced by rural livestock farmers in the Free State Province of South Africa, we model the distribution of faecal egg counts of parasitic helminths in sheep and goats. Excess zeroes in the data results in over-dispersion, which we address by fitting Poisson, negative binomial (NB), zero inflated Poisson (ZIP) and zero inflated negative binomial (ZINB). The proposed zero inflated models explicitly isolate unexposed animals within an infected group, making them ideal for selection purposes. Distributions of parasite egg count data in both sheep and goats were zero inflated for all the species except for strongyle egg counts in goats, which fitted negative binomial distribution. Rainfall, season and site were found to be predominantly significant in determining the distribution of parasites among their host. The findings on how the covariance structure relates to the distributional assumptions assist in the formulation of the necessary interventions. For instance in setting strategies to control gastrointestinal parasite infections or in identifying animals with the desired traits. Subsequently improving the livelihood of the rural communities.