Factors associated with Giardia infection in dogs in southern Ontario, Canada

Information concerning risk factors associated with Giardia infection in dogs in southern Ontario, Canada, is currently lacking. This study therefore aimed to identify risk factors for Giardia infection in dogs that visit off-leash dog parks in southern Ontario. From May-November 2018, fecal samples were collected from 466 dogs in 12 off-leash dog parks in the Niagara and Hamilton regions of Ontario. A survey that asked questions pertaining to travel history (i.e., area of residence, locations and regions visited in the previous 6 months), basic medical history (i.e., spay/neuter status, veterinary visits, use of deworming medication), consumption of a raw diet, and the physical (i.e., age, sex, breed) and behavioral characteristics (i.e., off-leash activities, hunting activities) of each dog sampled was administered to the respective owner. All fecal samples were examined with the Giardia plate ELISA (IDEXX Laboratories) for parasite antigen. Multivariable logistic regression analyses were conducted on the survey data to investigate putative risk factors for Giardia infection. Overall, 11.8% (95% CI: 9.2-15.1%) of samples tested positive for Giardia antigen. Results from the multivariable logistic regression analyses identified an interaction between dog age and spay/neuter status that was significantly associated with Giardia infection. The odds of infection were greater in intact as compared to neutered adult dogs (OR: 3.6, 95% CI: 1.7-7.9, p = 0.001), and in neutered juvenile dogs as compared to neutered adults (OR: 5.2, 95% CI: 2.2-12.2, p < 0.001). The results provide veterinarians with evidence-based information for identifying dogs at greatest risk of Giardia infection in southern Ontario.