Cysticercus ovis in Canadian sheep: risk factors and a transmission model to assess control measures
This thesis investigated the epidemiology and control of Cysticercus ovis infection on Canadian sheep farms. Canadian slaughter data indicated an increase in sheep carcass condemnations due to C. ovis in 2007 and 2008. Trace-back of 237 carcasses condemned in Ontario, between 2009 and 2011, revealed they originated from 133 farms across Canada. A case-control study was performed (n=40 cases, 56 controls) to identify farm-level risk factors for carcass condemnations. Farm dogs scavenging deadstock (OR=4.04; 95% CI: 1.16–14.04) and failing to dispose of deadstock properly (OR=11.78; 95% CI: 2.93–47.40) were significantly associated with condemnations in multivariable analyses. A transmission model for Taenia ovis was created and control options were assessed. Model simulations predicted cestocide treatment of guardian dogs every fifth week, and proper deadstock disposal would reduce the risk of C. ovis infection in lambs.