Recently Reported Rabies in Illinois

The three recent cases of rabies in domestic animals--a horse and a cow in northern Illinois and another horse in southern Illinois--remind us of the very real and present danger that is harbored in some of our native wild animals.

Rabies is an almost always fatal disease caused by an RNA virus in the family Rhabdoviridae. Any warm-blooded mammal can contract rabies, including domestic animals and humans. Several terrestrial wild animals in the United States are known reservoirs (or potential carriers) of the disease: foxes, skunks, coyotes, and raccoons. Additionally, several species of bats also serve as reservoirs for rabies virus.

Exposure to rabies occurs when saliva from an infected animal is passed to an uninfected animal. In most cases, this occurs via a bite wound. However, rabies transmission can also occur across mucous membranes, through exposure to aerosolized virus, and through transplantation of infected tissue. Once exposed, the host may show no signs of illness for several weeks while the virus spreads through the nervous system. When the virus reaches the brain, the host develops an acute encephalitis as the virus replicates and is shed in the saliva. Once the host displays signs of rabies, the disease is almost always fatal. Signs of rabies may be non-specific and include flu-like symptoms, fever, headache, muscle pain, agitation, confusion, abnormal behavior, and other central nervous system dysfunction.

Historically, rabies in wild animals has been most frequently reported in raccoons. These cases have been confined geographically to the east coast of the United States and have not been reported in Illinois to date. Skunks are the second most frequently reported wild species to carry rabies, followed by bats, foxes, and other wild mammals. It is generally accepted that the most common wild reservoirs for rabies in Illinois are bats and skunks. In 2004 fifty-one animals tested by the state were positive for rabies, according to the Illinois Department of Public Health: 50 bats and one horse.

Only 100 of the 4,607 animals submitted for testing last year were skunks and none tested positive. Understandably, people may be less likely to approach or handle these noxious-smelling nocturnal mammals, which could account for the paucity in the number of animals submitted for testing. Striped skunks, with scent glands that hold about a tablespoon of musk containing mercaptans, can spray up to 15 feet and can be smelled a mile away.

The horse from LaSalle County, December 2004, and the cow from Bureau County, January 2005, were found to be infected with a skunk strain of rabies. This may indicate that the incidence of skunk rabies is on the rise. Tests are pending on the horse from Fayette County that tested positive in January 2005.

Officials are asking that surveillance be increased to detect any emerging patterns in the disease. Wild animals infected with rabies do not always present with the classic depiction of the foaming mouth and vicious behavior. Signs of the disease may be more subtle and may include overly friendly behavior, abnormal daytime sightings of nocturnal animals, or sightings of animals in the same location over prolonged periods. If a wild animal, particularly a skunk, is suspected of having rabies, local animal control or public health agencies should be notified.

Prevention of rabies is of utmost importance. Vaccinate pets and livestock against rabies and report bites or possible exposure promptly to your veterinarian or health care provider.

For more information on rabies and the recent cases of rabies in Illinois, visit the Centers for Disease Control and Prevention at http://www.cdc.gov/ and Illinois Department of Public Health http://www.idph.state.il.us/.