Pilot Study: Distribution and prevalence of Theileria orientalis genotypes in adult lactating cows in Western Australia dairy herds

An emerging tick-borne disease, bovine anaemia due to Theileria orientalis group (BATOG), is a serious problem for the cattle industry, causing substantial mortality in cattle, resulting in significant production loss and economic loss. BATOG is caused by a blood-borne intracellular protozoan parasite, Theileria orientalis, causing damage to the erythrocytes and ultimately severe anaemia, transmitted by the Australian bush tick (syn. Asian longhorned ticks, New Zealand cattle tick), Haemaphysalis longicornis. T. orientalis was first recorded in Australia in the 1900s and infection was considered nonpathogenic, however clinical disease cases of BATOG has increased significantly since 2006 due to the emergence of pathogenic T. orientalis genotypes, although the distribution and prevalence is not well understood in Western Australia (WA). Therefore, this pilot study conducted on 100 cattle from 10 dairy farms in the greater South-West region of WA aimed to provide the first insight into the distribution and prevalence of T. orientalis genotypes. In this study, molecular screening using polymerase chain reaction (PCR) detected Theileria at a prevalence of 13% (13/100) and Sanger sequencing was performed on 13 dairy cattle blood samples to identitfy T. orientalis genotypes. Results revealed that T. orientalis was widespread throughout the South-West region of WA, especially along the coastal margins. The prominent T. orientalis genotype was identified as the Ikeda genotype (11%), while the Buffeli genotype was identified in WA for the first time, albeit with a low prevalence (1%). These data highlight the importance of conducting widespread surveillance programs for increasing the understanding of BATOG in WA, for improving current cattle tick control programs and stock management in WA and developing future research and biological surveillance strategies