Investigations into the host specificity of Theileria taurotragi

All Theileria parasites have definitive natural hosts that act as carriers. Incidental infections of uncommon hosts do occur raising questions regarding host specificity and its drivers. Reported hosts for Theileria taurotragi include bushbuck, cattle and eland. More recently T. taurotragi was detected in African buffalo, which may have implications for accurate diagnostics of T. parva. The current study therefore investigated the host specificity of T. taurotragi by developing a specific and sensitive real-time Taqman PCR assay. Animals were screened from areas where Rhipicephalus appendiculatus, the tick vector for both T. parva and T. taurotragi was present. While T. taurotragi was detected in cattle, eland, kudu and nyala, African buffalo (n = 352) was negative. Conversely, these same buffalo showed a prevalence of 72-100% for T. parva. While transmission of T. taurotragi to cattle was successful using the same infected tick batch, transmission to African buffalo did not occur. The results suggest that African buffalo is not a natural host of T. taurotragi and would probably not harbor anti-schizont antibodies against T. taurotragi. This would preclude T. taurotragi as possible source of cross-reactivity in the T. parva immunofluorescent antibody test. Host specificity of T. taurotragi for members of the Tragelaphini, but not buffalo also suggests that host specificity may have been an important driver in the speciation of the T. taurotragi clade. Different scenarios for co-evolution of host and parasite are discussed with implications for time of divergence for this Theileria clade.