Development of an enzyme-linked immunosorbent assay for the diagnosis of Theileria sp. infection in sheep

A rapid, sensitive and specific diagnostic method, an enzyme-linked immunosorbent assay (ELISA), was developed for the diagnosis of Theileria sp. infection in sheep; and optimal conditions were established, such as antigen concentration, serum dilution, coating time, Tween-20 concentration and conjugate. The results were analyzed by measuring the coefficient of variation (CV). Three sera titers (high, middle, low) were analyzed over the measurement range, resulting in a CV of around 10%, whereas a 30% variation is the maximum acceptable. The cut-off value was determined by the mean of a negative control plus three standard deviations. Cross-reaction was found only with Babesia ovis. However, this result may be questionable, because it cannot be excluded that these sheep were already infected with both Theileria sp. and B. ovis. The ELISA described in the present study proved to be a useful tool for studying the epidemiology of Theileria sp.