Dog Bites and Rabies Risk in Tennessee

BACKGROUND: Canine-variant rabies has been eliminated from the United States. However, many assume that dog bites pose a substantial risk for rabies transmission, resulting in frequent canine submissions for rabies testing as well as administration of rabies post-exposure prophylaxis (rPEP) to humans. We hypothesized that dog bites in Tennessee actually present a very low risk for rabies transmission, and that rPEP is over-prescribed for dog bites.

METHODS: We collected detailed clinical information on dogs testing positive for rabies in Tennessee from 2008 through 2013 by interviewing the animal owner, veterinarian, or both. Additionally, we analyzed records of dogs tested for rabies at the Tennessee State Public Health Laboratory to assess whether rabies-positive dogs were more or less likely to have bitten a person than were rabies-negative dogs. Finally, we analyzed hospital discharge data from 2007-2011 to assess rates of rPEP administration within Tennessee.

RESULTS: Among 25 dogs testing positive for rabies between 2008 and 2013, none were documented to have bitten a person. The most commonly reported clinical signs were anorexia (86%) and ataxia (75%). Aggressiveness was reported in only 12% of dogs. In every case, animals were tested for rabies due to presentation of a neurological illness and the potential for non-bite exposures. Retrospective review of 5818 laboratory submissions from 2002 through 2013 identified only 2 (6%) of 38 rabies-positive canines with history of biting a person documented on the laboratory accession form. Of 5714 negative canine tests, 4370 (76%) indicated a history of biting a person. Dogs without a reported bite were significantly more likely to test positive for rabies than were dogs with a reported bite (OR 98; 95% CI 23, 409). According to hospital discharge data, an average of 300 patients received rPEP in Tennessee per year during 2007-2011, and 50% of these patients presented with dog bites.

CONCLUSIONS: In Tennessee, dog bites do not carry a significant risk of rabies transmission. Apparently healthy dogs are not found to be positive for rabies and do not pose a risk for transmission of rabies. Dogs infected with non-canine variant rabies viruses are profoundly ill with neurologic signs and rarely display aggressive behavior or bite. Rabies post-exposure prophylaxis is seldom necessary for dog bite victims; however, dog bite victims frequently receive rPEP. Consideration should be given to revision of national recommendations regarding rabies risks from biting canines in the United States.