William Shulaw, D.V.M.
Randall E. James, Ph.D.
Rabies is a viral disease of the central nervous system of mammals. The infection creates a progressive inflammation of the brain. In the United States, the primary reservoir for the virus is in wildlife; domestic animals are usually exposed by contact with infected wild animals. Bats, skunks, and foxes are the usual culprits for spreading infection in Ohio. In recent years, raccoons in the eastern United States have been severely affected by the rabies virus. This epizootic (epidemic) is slowly spreading toward Ohio. Several counties in Pennsylvania and West Virginia that border Ohio have diagnosed raccoons with rabies. A cat and two raccoons with the raccoon strain of the virus were found in eastern Ohio in early 1996. Humans can contract rabies from wildlife or domestic animals.
In 1994, four of 2,855 specimens submitted to the Ohio Department of Health were diagnosed positive for rabies. In 1995, 10 bats, one horse, and one fox tested positive, and as of June 1996, one bat, two raccoons, one cat (raccoon strain) and one fox were found positive. In 1995, 20 people received post- exposure treatment after exposure to bats; two others received treatment because of exposure to the horse.
The rabies virus is spread by contact with saliva from an infected animal, usually through bites or scratches, abrasions, or open wounds in the skin. Domestic animals may become exposed during normal grazing or roaming. Occasionally, rabid wild animals will enter barns, paddocks, and lots. Livestock are often exposed when they investigate this new animal in their surroundings. Because people can be exposed to rabies by contact with wild or domestic animals, avoid "suspicious" animals.
The classic, or "furious," form of rabies may occur in livestock or pets. The animal appears nervous and agitated, or becomes aggressive, attacking other animals and people. However, the main symptom is unusual behavior, which gradually leads to depression or partial paralysis. Cows typically develop a hoarse bellow. Drooling and abnormal swallowing may make them appear to have something caught in their throats. Some animals may only show depression and weakness, or partial paralysis, of the hindquarters. During the course of several hours to a few days, the animal will go down, develop convulsive seizures, and die. Sheep have symptoms similar to cattle, and sometimes vigorously pull their wool. The disease is often seen in more than one sheep in a flock because the animals stay close together and several can be easily bitten at one time. Goats with rabies are often aggressive and bleat continuously.
Horses tend to contract the paralytic form of the disease and may initially show abnormal postures with wobbliness of the hindquarters, frequent whinnying, unexplained aggressiveness (with kicking and biting), and signs of colic. They may also show lameness in one leg, followed by an inability to rise the next day. Pigs with rabies tend to act excited and uncoordinated. Some animals will chew rapidly, salivate, and convulse. Paralysis eventually occurs and death follows in 12 to 48 hours.
The symptoms seen in rabid animals may be quite variable, making early detection difficult. In addition, other diseases, such as nervous ketosis in dairy cows or pseudorabies in pigs and other livestock, may mimic some of the signs of rabies. For these reasons, owners should isolate animals showing suspicious behavior or other signs so they may be observed carefully, and precautions should be taken to avoid injury by them. A veterinarian should be consulted to determine whether rabies should be considered in the diagnosis.
All dogs and cats should be routinely vaccinated for rabies. Vaccination programs have reduced laboratory confirmed cases of rabies in dogs from 6,949 in 1947 to 153 in 1994. For the third straight year, however, the number of cases in cats (267 cases in 1994) has exceeded that of dogs in the United States, pointing to a need to develop better vaccination and control programs for cats.
A number of rabies vaccines are available for domestic animals. All of the vaccines are killed, or inactivated, so they cannot cause disease. Several products are licensed for dogs, cats, cattle, sheep, and horses. No products are currently licensed for goats, pigs, exotic animals (except ferrets), or captive wild animals. Vaccination of animals for which no approved product exists can create a false sense of security.
Livestock and horse owners may decide to vaccinate their animals if they are often exposed to potentially rabid wild or domestic animals. Although pastured animals are generally at greater risk, rabid animals, especially stray cats and dogs, may still enter a building and expose farm animals. Generally, production animals, such as dairy cow herds and sheep flocks, are not vaccinated because the potential risks are usually lower than the annual costs of vaccination and because human contact with individual animals is low. Small groups of valuable purebred animals may be an exception. Horse owners may choose to vaccinate their animals because of the close contact they have with their horses. In recent years, a few states have required vaccination for rabies before an animal (including some livestock) is exhibited. Owners should inquire about this before making plans to travel. Your veterinarian can be of great help in making the decision about the need for rabies vaccination.
Vaccination of people in high-risk jobs, such as veterinarians, wildlife personnel, and animal control officers, is often recommended. Humans are routinely vaccinated following a potential exposure. Livestock owners should immediately consult with their physicians if they think they could have been exposed to a rabid animal, and for advice concerning the potential value of pre-exposure vaccination.
Stray cats, dogs, raccoons, and other wildlife in and around barns and other farm buildings can increase the risk of rabies. Make your farm less attractive to these animals by eliminating nesting, hiding, and roosting places, and by using specific deterrents, such as screening potential entry points. Never feed stray animals or wildlife, and don't allow pet food or garbage to remain in open, unsecured containers. Vaccinate or eliminate dogs and cats on your farm. For more information on wildlife control, contact the Ohio Department of Natural Resources, Division of Wildlife.
Animals that demonstrate changes in behavior, especially extreme nervousness or aggression, difficulty in swallowing or signs of choking, changes in voice, or other suspicious signs should be treated with caution and isolated. A veterinarian who can help make a diagnosis of possible rabies should be contacted. Rabies suspects are tested by the Ohio Department of Health laboratories. Arrangements for testing can be made through your veterinarian, local health department, and the Ohio Department of Agriculture, Animal Disease Diagnostic Laboratory.
Gary Bowman, D.V.M.,
Kent Hoblet, D.V.M.,
Richard Novak, D.V.M., and
Teresa Morishita, D.V.M
All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.
Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
TDD No. 800-589-8292 (Ohio only) or 614-292-1868