A Study of the Epidemiologic States of Theileriosis in a Range of Smallholder Dairy Farms in Kenya

Abstract Endemic stability describes a dynamic epidemiological state in which clinical diseases are rare in spite of high infection prevalence in the population. Better appreciation of this concept in relation to tick-borne diseases would support the development of better control strategies. We conducted a study in four distinct smallholder dairy production systems in Kenya to characterise the epidemiological states of Theileria parva infection and identify the important determinants of those states. Maragua, Kiambu, Uasin Gishu and Kakamega districts were selected for the study. In each site, stratified random sampling was used to select 250 smallholder farms for a cross-sectional study to estimate sero-prevalence of T.parva antibodies in calves. This was followed by an intensive longitudinal monitoring of 80 randomly selected farms for one year. The incidence of T.parva infection, cause specific mortality, tick attachment rate, the prevalence and intensity of Theileria infection in ticks and husbandry practices at the farm level were monitored. The study identified Kakamega to be endemically stable to tickborne diseases. The other sites were at different levels of endemic instability. The major determinants of the epidemiological state were found to be biophysical factors (environmental suitability for vectors and breed composition) and husbandry practices (grazing management and tick control)