Investigating the first outbreak of oriental theileriosis in cattle in South Australia using multiplexed tandem PCR (MT-PCR)

This study investigated the first outbreak of oriental theileriosis in a herd of beef cattle in South Australia using a newly established multiplexed tandem PCR (MT-PCR) to identify, differentiate and quantitate the four genotypes (buffeli, chitose, ikeda and type 5) of Theileria orientalis recognised to occur in Australasia. Following clinical diagnosis of oriental theileriosis (based on clinical signs, laboratory findings and post mortem examination), 155 blood samples were collected from individual cows (n = 85) and calves (n = 70), and tested by MT-PCR. In total, 117 (75.48%) cattle were shown to be test-positive for T. orientalis. All four genotypes were detected, and ikeda had the highest prevalence (90.6%; 106/117), followed by buffeli (83.8%; 98/117), chitose (18.8%; 22/117) and type 5 (5.1%; 6/117). Mixed infections with genotypes buffeli and ikeda had a higher prevalence (55.5%; 65/117) than any other combination of genotypes. The prevalences of buffeli and ikeda were significantly higher (P < 0.005) than those of chitose and type 5. The average intensity of infection with genotype ikeda (329,775 DNA copies) was significantly higher (P < 0.0001) than buffeli (212,843) and chitose (125,462). This study reinforces the utility of MT-PCR as a diagnostic tool for rapidly investigating oriental theileriosis outbreaks in cattle herds and as a pre-movement screening test for preventing the introduction of this disease into non-endemic regions.