Rabies is an acute, fatal viral encephalomyelitis found worldwide, and is caused by infection with a virus from the genus Lyssavirus. Lyssaviruses are adapted to replication in mammalian neural tissue and do not persist in the environment. Transmission occurs primarily through the bites of infected carnivores and bats in the final stage of the disease. Major North American wild reservoirs are raccoons, coyotes, skunks, foxes, and bats. Small rodents and lagomorphs (rabbits and hares) are almost never found to be infected with rabies.
There are no specific clinical signs of rabies infection beyond acute behavioral changes. After an incubation period, which can last from less than 10 days to several months, encephalopathy and death occur within days. Nonspecific signs during incubation may include restlessness, vomiting, and diarrhea. Acute behavioral changes in wild animals include apparent loss of wariness and caution, head tilt, lolling tongue, drooling, dropping of the lower jaw, disorientation, hyperactivity, and convulsive seizures.