Distribution of Theileria orientalis in Virginia Market Cattle, 2018-2020

Theileria orientalis, genotype Ikeda, was recently detected in North America. Determining the emerging distribution of this pathogen is critical for understanding spread and developing management strategies. Whole blood samples were collected from cattle at Virginia livestock markets from September 2018 through December 2020. Animals were tested for T. orientalis using a universal and then genotype specific real-time PCR based on the MPSP gene. Prevalence for each genotype was analyzed for temporal trends and mapped by county. Spatial patterns were compared between genotypes and assessed for associations with habitat features, cattle movements through cattle markets and county proximity. Overall, 212 of 1980 samples tested positive for T. orientalis with an overall prevalence of 8.7% (172/1980) for genotype Ikeda, 1.8% (36/1980) for genotype Chitose, 0.2% (3/1980) for genotype Buffeli. The Ikeda genotype increased over time in northern and southwestern Virginia markets. The Ikeda and Chitose genotypes occurred in different regions, with little overlap, but for each genotype, spatial distribution was associated with a combination of cattle movements and environmental factors. Genotype specific qPCR testing and surveillance of cattle from across a wide area of Virginia are providing information on temporal, spatial, and other patterns for this emerging disease.

Automated summary

This study investigates the distribution and prevalence of Theileria orientalis pathogen in North America, and analyzes the spatial distribution of different genotypes and their associations with environmental factors and cattle movements. The study finds that the prevalence of Ikeda genotype increases over time in northern and southwestern Virginia markets. Genotype specific qPCR testing and surveillance provide important information for understanding the spread of this emerging disease.