Exploring the geographical distribution of cryptosporidiosis in the cattle population of Southern Ontario, Canada, 2011-2014

Cryptosporidiosis is an infectious disease of relevance to the cattle industry. The southern region of the Canadian province of Ontario is characterised by widespread cattle farming that is a key contributor to the Canadian dairy industry. Given Ontario's key role in the Canadian dairy industry and the potential impact that cryptosporidiosis can have on cattle operations, identifying areas of increased risk for bovine cryptosporidiosis is important. The primary goal of this study was to explore the distribution of bovine cryptosporidiosis, across the geographical areas served by the 29 Public Health Units (PHUs) of Southern Ontario, in the period 2011-2014. Laboratory data on bovine cryptosporidiosis were collected from the Animal Health Laboratory at the University of Guelph, Canada. Using veterinary clinic locations as a proxy for farm location, choropleth and isopleth maps were produced. Highrisk clusters of bovine cryptosporidiosis were identified using the flexible spatial scan test. Assessment of the potential for spatial misclassification bias resulting from a proxy location variable was conducted. The overall raw farm-level prevalence of bovine cryptosporidiosis was 45% [95% confidence interval, CI: 42%-48%]. A cluster was identified in the central-west region of Southern Ontario (relative risk 1.30 [95% CI: 1.07-1.54, P=0.026]) meaning that cattle in the areas served by the Bruce-Grey-Owen Sound, Huron, Wellington-Dufferin Guelph and Waterloo PHUs were at a higher risk for infection. Given that this area is known for having a high-density of dairy cattle, it should be considered as a target for further surveillance.