Health Risk in Humans Associated with Free-Roaming Domestic Dogs on the Northern Cheyenne Reservation, MT

The Northern Cheyenne Reservation in Montana has a large free-roaming dog population. Given the potentially poor health condition of the dogs and potential contact with livestock, wildlife, and ectoparasites, these free-roaming dogs pose a potential zoonotic disease risk to the Northern Cheyenne community. This study aimed to assess the risk of zoonotic transmission based on animal ownership practices, and investigate the potential association between contact with free-roaming dogs and illness in humans. Data were collected through a questionnaire administered to Northern Cheyenne Reservation residents and analyzed through basic descriptive statistics and multivariate log binomial modeling. A total of 59 residents were surveyed in December of 2013. The majority (71%) of participants reported owning dogs, with most owners reporting owning dogs that were primarily confined to the home (68%), semi-confined (71%), and/or free-roaming (51%). Veterinary care was generally low (56%), and a majority of owners reported having to treat their dogs for fleas/ticks in the past year (93%). Most dog owners also reported that they had dogs that have regular contact with livestock (61%), but not with wildlife (30%). Unadjusted prevalence ratios showed evidence of an association between contact with free-roaming dogs and having 2 or more illness in the past year (moderate frequency contact: PR=3.07, 95% CI: 1.44–6.52); high frequency contact: PR=2.61, 95% CI: 1.24–5.50). Contact was also associated with specific types of illness (i.e. gastrointestinal, respiratory, and generalized malaise), though valid estimates could not be calculated. Multivariate modeling controlling for confounding, however, showed no statistically significant associations between contact and frequency of illness (moderate frequency contact: PR=1.4, 95% CI: 0.95–2.06; high frequency contact: PR=1.38, 95% CI: 0.92–2.07). The smaller than expected sample size hindered the statistical power of the study, and prevented us from fully exploring the association between free-roaming dogs with specific types of illness. While this study did provide some support that the free-roaming dogs on the reservation may be impacting the community’s health through transmission of zoonotic diseases, further data collection is required to obtain more precise results.