Abstract

Disease is increasingly recognized as a threat to the conservation of wildlife, and in many cases the source of disease outbreaks in wild carnivores is the domestic dog. For disease to spill over from a domestic to a wild population, three conditions must be satisfied: susceptibility of the wild species, presence of the disease agent in the domestic population, and contact between the two populations of interest. This study investigated the potential for disease spillover from the domestic dog population to the wild carnivore population in the Isoso of Bolivia, an area of tropical dry forest contiguous with a national park. Using questionnaires, data were gathered on the demographics of dogs, including adult and neonatal mortality, litter size, and hunting frequency. A large (6475 hunts) dataset containing self-recorded hunting information from 1996 to 2002 was analyzed to determine the extent of dog participation in hunting and duration, success, and frequency of hunting trips. Blood samples were taken from 98 Isoceño dogs for a serosurvey of canine pathogens of conservation concern, including canine distemper virus, canine parvovirus, canine herpesvirus, canine coronavirus, canine adenovirus, leptospirosis, toxoplasmosis, canine brucellosis, heartworm disease, and the sarcoptic mange mite.

Results from the demographic portion of the study indicate that the number of dogs present in the Isoso is remarkably high. The ratio of people to dogs is approximately 1.5:1, and each household has an average of 3.8 dogs. This is equivalent to more than 500 dogs in a village with a human population of 760. The average age of dogs is relatively low (3–4 years), and the average litter size is 4.1 pups. These values, along with high neonatal (80%) and adult (38%) mortality rates, indicate that the population turnover among dogs is quite high, suggesting that the population is large enough to support diseases endemically by providing a constant source of susceptible hosts. Most (86%) dogs participate in hunting, and of these dogs, 82% hunt weekly or more often. The vast majority (97%) of hunts include dogs. The average hunt is 10 hours long and involves 2.8 dogs. Based on the average number of dogs participating in hunts, and the frequency and duration of hunts, the forest surrounding the Isoseño communities is subjected to an average of 30,000 dog-hour each week. Results of the serosurvey demonstrate a high seroprevalence of canine distemper virus (95%), parvovirus (95%), herpesvirus (68%), and sarcoptic mange (63%). These findings, as well as the high population turnover of dogs and frequent opportunities for contact between domestic and wild carnivores, indicate that domestic dogs represent a disease risk for wildlife in the Bolivian Isoso.