Estimating the Transmission Dynamics of Theileria equi and Babesia caballi in horses

SUMMARY For the evaluation of the epidemiology of Theileria equi and Babesia caballi in a herd of 510 horses in SW Mongolia, several mathematical models of the transmission dynamics are constructed. Because the field data contains information on the presence of the parasite (determined by PCR) and the presence of antibodies (determined by IFAT), the models cater for maternal protection with antibodies, susceptible animals, infected animals and animals which have eliminated the parasite and also allow for age-dependent infection in susceptible animals. Maximum likelihood estimation procedures are used to estimate the model parameters and a Monte Carlo approach is applied to select the best fitting model. Overall, the results are in line with previous experimental work, and add evidence that the epidemiology of T. equi differs from that of Babesia spp. The presented modelling approach provides a useful tool for the investigation of some vector borne diseases and the applied model selection procedure avoids asymptotical assumptions which may not be adequate for the analysis of epidemiological field data. INTRODUCTION Equine piroplasmoses are caused by the two intra-erythrocytic protozoa Theileria equi and Babesia