Recently Reported Rabies in Illinois
Dr. Julia Whittington, Wildlife Extension Veterinarian, University
of Illinois College of Veterinary Medicine
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/.