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Rabies in Cattle Often Leads to Human Exposure
4/24/2008
Mick Livingston
Extension
Agent (4-H/Youth)
Colorado State University Extension
Golden Plains
Area |
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This article is from Dr. Roger W. Ellis DVM Extension Veterinarian
Colorado State University.
Rabies is a fatal zoonotic disease with
serious public health risks. The disease is an acute progressive viral
encephalitis that all mammals are susceptible to and is maintained within wild
mammal populations. Pet owners are widely aware of the threat of rabies through
educational programs and vaccination regulations. Cattle and horses are
frequently infected with rabies and place animal handlers at considerable risk
of exposure. Since 2000, only cats have exceeded cattle in the incidence of
rabies cases amongst U.S. domestic animals. People that handle cattle often do
not recognize the potential risk that cattle with vague or misrepresentative
symptoms create for human exposure and infection. Human exposure to rabies via
infected cattle occurs commonly and poses serious consequences.
Cattle
most frequently become infected with rabies through contact or bite wounds from
wild animals. Raccoons, skunks, coyotes, foxes and bats are the most common
wild animal sources and are well adapted to areas where cattle are raised. The
incubation period from viral exposure to the development of symptoms is highly
variable; ranging from 3 weeks to 3 months, with isolated case reports up to 6
months. Generally, the knowledge of past wild animal exposure or bite wounds is
unknown.
Symptoms of rabies in cattle vary considerably and are often
confused with other conditions. Initial signs may be quite mild and include
depression, not eating or drinking, isolation, and lameness. Often, only
changes in normal behavior are the early signs. As the disease progresses,
other findings may include: the inability to swallow may cause
slobbering-excessive salivation, head drooping, difficulty in walking or
standing, and signs of pain. Unprovoked and repeated bellowing is often
recognized and repeated straining to urinate or defecate is common. Some,
however, not all infected cattle, will become severely aggressive and will
attack people, other cattle or animals, inanimate objects and are serious risks
of injury to all. Progression to full paralysis generally occurs and most
affected animals die within one week from the time signs are first
detected.
Due to the vagueness of signs and lack of consideration of
rabies as a potential diagnosis, cattle handlers, veterinarians and other
people in contact are often exposed to the virus. During the active course of
the disease, the virus is excreted at high levels in saliva. Often the symptoms
of slobbering and difficult swallowing dispose people to attempt to examine the
mouth, which affords contact with virus-laden saliva and possible bite wounds.
Virus may be introduced into bite wounds, open skin wounds, or onto mucous
membranes of the mouth and eyes. Rabies infection should be considered in all
cattle with abnormal behavior or neurological signs that cannot be clearly
diagnosed. All suspicious cases should be examined by a veterinarian to
differentiate the disease risks and to propose further recommendations. Cattle
that die under similar suspicious conditions should be autopsied (post-mortem
exam) and the brain collected for submission and testing. Public health
officials should be contacted and medical advice should be received for all
exposed humans. The carcass should be disposed of in a manner that prevents
further animal/human contact. Consideration should be given to other animals,
especially pets, which also may have been exposed. If a herd exposure is
significant, state regulatory veterinarians should determine the public and
animal health ramifications and determine the course of
action.
Prevention of rabies is not an easy task due to the
unpredictable exposure to wild animals with rabies. Vaccines approved for use
in cattle, sheep and horses are available and should be seriously considered
for high-risk exposures or high-value animals. Due to costs of vaccine and
relative low incidence rates, vaccination is not routinely used in most cattle
herds. Wildlife control should be a concern for all cattle operations,
particularly in areas with increased reports of wild or domestic animals
testing positive for rabies.
Although rabies occurs at low incidence
rates in cattle, the threat is present due to maintenance of the viral
infection in wild animals. The most serious threat is the exposure of humans to
rabid cattle due to lack of awareness and difficulty in correct diagnosis prior
to handling and treatment attempts. In any situation of suspicion of rabies, a
veterinarian should be contacted and samples submitted for diagnostic testing.
A little extra-precaution is warranted due to the fatal outcome of rabies in
all animals, and prevention of human exposure is paramount.
Further
information can be obtained through:
Colorado Department of Public Health and
Environment
Colorado Dept.
of Agriculture - Animal Industry Division
Colorado State University College of
Veterinary Medicine and Biological Sciences
Colorado State University Veterinary
Diagnostic Laboratory
Colorado
Veterinary Medical Association |
Page Created and Maintained by: Perry D. Brewer, Area
Extension Agent (Technology Education/Youth)
4/24/2008 |
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