Learn About Rabies in Wild Animals

2010-05-13

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Rabies in Wild Animals

Rabies is one of the oldest infectious diseases known to humans. Over 4,000 years ago, in 2300 B.C., dog owners in parts of Babylonia had to pay heavy fines if their rabid dogs killed people by biting them and infecting them with rabies. During a rabies outbreak in London from 1759 to 1762, a reward of two shillings per dog was offered for shooting any dog running loose in the city. In 1026 A.D., Howel the Good, living in Wales, wrote about madness in dogs; this is the earliest record of rabies in Great Britain. Rabies spread through Europe during the eighteenth century. In 1703, a priest in Mexico reported the first recognized case of rabies in the Americas. In about 1770, rabies outbreaks were reported in dogs and foxes in Boston and around other North American towns.

It is believed that the rabies virus originated in wild animals such as bats. However, all warm-blooded animals, including humans, are susceptible to rabies. On average, symptoms of rabies will develop within a couple of months after an animal is infected with the virus. When an animal exhibits the “furious” form of rabies, it may become aggressive and extremely sensitive to touch. The term “rabies” comes from the Latin word rabere, which means to rage or rave. In the “dumb” form of the disease, an infected animal may become lethargic and weak. Its head and neck muscles may become paralyzed. Because some victims avoid drinking water, possibly due to paralyzed throat muscles, the Greeks named human rabies hydrophobia, which means fear of water.

Rabies is caused by a virus that affects the central nervous system. Starting in 1881, Emile Roux, a physician/scientist, worked with the French chemist Louis Pasteur to produce a rabies vaccine. The vaccine was presented in 1883. In 1885, after being mauled by a rabid dog, Joseph Meister was the first human being successfully treated with the new vaccine. Prior to the development of a vaccine, rabies was invariably fatal.

Rabies vaccinations have been available for domestic animals for many years, but until recently this kind of preventive measure did not exist for wild animals. During the last 30 years, oral rabies vaccine has been field-tested in the United States, Canada, and Europe on free-ranging raccoons, gray foxes, and coyotes. A wild animal that eats a bait containing the oral rabies vaccine will create rabies antibodies within two to three weeks, making it immune from rabies infection due to bites from other animals.

When an animal is infected with the rabies virus, one of the areas of the body where the virus will become concentrated is the salivary glands. If an infected individual bites another human or animal, the rabies virus that is present in the saliva can easily enter the body of the bit victim. Once the saliva of an infected animal enters the body of another animal through a bite wound, the virus travels through the nervous system to reach the brain. When it reaches the brain, the virus will multiply and migrate to the salivary glands. This is the most common way in which the rabies virus is transmitted. It is also possible for rabies to be transmitted if the saliva or brain tissue of an infected animal comes into contact with the open wounds or mucuous membranes of another animal; however, non-bite transmission of the rabies virus is rare. The rabies virus cannot be spread through casual contact, such as simply touching an infected animal, or through contact with uninfected tissue.

Today, rabies continues to be a challenge for wildlife managers and public health officials. Rabies management has become more complex in the last 30 years because wild animals have replaced domestic dogs as primary carriers of the disease. Skunks, raccoons, foxes, coyotes, and bats are the wild animal species that most often become infected with rabies. According to the Center for Disease Control and Prevention, 90% of currently-reported rabies cases reported in the United States involve these wildlife species.