Co-Infection of cattle in Virginia with Theileria orientalis ikeda genotype and Anaplasma marginale

Theileria orientalis ikeda is a newly identified agent of bovine infectious anemia in the United States. Although it is transmitted by separate tick hosts than Anaplasma marginale - a bacterial etiology of bovine infectious anemia -the geographic distributions of these two infectious organisms overlap, with co-infection reported in some cattle. Only anaplasmosis has approved effective treatment in the United States. To provide rapid diagnostic information for producers with anemic animals, we developed a duplex qPCR for A. marginale and T. orientalis. With a cut-off of 38 cycles, the duplex assay has a sensitivity of 96.97% and a specificity of 100% for A. marginale; with a cut-off of 45 cycles, the duplex assay has a sensitivity and a specificity of 100% for T. orientalis. In addition to providing a tool for improved clinical decision-making for veterinarians and producers, this qPCR facilitates the study of co-infection rate of cattle in Virginia. Of 1,359 blood samples analyzed, 174 were positive for the presence of T. orientalis, 125 were positive for the presence of A. marginale, and 12 samples were positive for both T. orientalis and A. marginale. This indicated that co-infection of both of these etiologies of bovine infectious anemia does occur within the state of Virginia. It is likely that this pattern of infection will be seen in regions where T. orientalis and A. marginale are endemic, despite the difference in tick vectors.