Biosecurity and Health Committee:
Protocol for the Management of Rabies in Racehorses

Table of Contents

1. Disease Information
2. Human Risk Data
3. Horse Health Risk Data
4. Ecology Information
5. Prevention
6. Regulatory Information
7. Committee's Recommendations
8. More Information

Section 1: Disease Information

Rabies is a sporadic, but highly fatal, zoonotic disease caused by a virus (Lyssavirus). It persists in Ontario wildlife, primarily in the red fox and striped skunk. All warm-blooded animals can be infected with rabies but it is most often transmitted in Canada by foxes, raccoons, skunks and bats. Variation in susceptibility is noticeable. Foxes, rats and coyotes are extremely susceptible; cattle, rabbits, and cats are highly susceptible; dogs, sheep and goats are moderately susceptible; and opossums little, if at all. The virus is almost always spread by saliva from the bite of an infected animal. In addition, but more rarely, rabies can be spread when virus from saliva is introduced into open cuts or wounds or comes in contact with a mucous membrane in areas such as the mouth, nasal cavity, or eyes.

Section 2: Human Health Risk Data

Rabies affects both animals and humans. In the past 50 years, less than 10 humans have contracted rabies in Canada. Five cases of rabies in humans were reported in the United States and Canada during September and October 2000. The most recent Canadian death from rabies was a 9-year-old Quebec boy who died in October 2000. He was suspected of being bitten by a bat. One human in Ontario was killed by a rabid horse. Rabid horses pose a serious threat to humans because they will bite each other and their handlers.

Section 3: Horse Health Risk Data

Horses of all ages are susceptible. The number of rabid horses in Ontario was zero from 1997 until the year 2000, when three horses were diagnosed with rabies (in Bruce, Grey and Huron counties). In 2001, five cases of horse rabies were reported (in Bruce, Dufferin, Simcoe, Thunder Bay, and Waterloo counties). There was one case in 2002 (Algoma) and one up to July 31 in 2003 (Grey). Horses are often exposed because they are curious creatures. They are apt to investigate a wild animal that is acting strangely and may be bit on the muzzle, face and/or lower legs. Clinical signs in the horse include behaviour changes ranging from aggression, ataxia (incoordination), paresis (partial paralysis), hyperesthesia (hypersensitivity to stimuli), fever, colic, lameness, and recumbency. The disease usually progresses to death in 4 to 5 days, although some horses will survive up to 15 days. The "furious form" was noted in 43% of rabid horses and clinical signs in some of these animals initially appeared as the "dumb form." The paralytic form was not observed. Horses which develop the "furious form" show excitement, become vicious, bite, kick, exhibit blind staggers, suddenly fall and may chew themselves or foreign objects.

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Section 4: Ecology Information

There are three different strains of rabies in North America, which are differentiated by their carrier species. The three strains include Arctic fox, raccoon and bat rabies. There are no differences between the strains as far as their ability to kill their carrier species, other animals and possibly humans. The disease persists in wildlife populations throughout the United States, Canada, Mexico, and other parts of the world. Wildlife infected with rabies may show no fear of man, be aggressive, or be incoordinated.

Section 5: Prevention

There is no effective treatment for rabies. Once clinical signs appear, rabies is fatal. Therefore, it is best to prevent exposure to the virus. If a person is bitten by an animal, wash the wound or exposed surface with soap and water, remove clothing that may be contaminated, contact your doctor immediately or go to the nearest hospital emergency.

Two inactivated (killed) rabies vaccines are marketed in Canada, Rabvac™ 3 (Wyeth) and Merial® Imrab® 3 (Merial). Foals born to non-vaccinated mares should receive a single 2-ml dose of vaccine starting at three months of age and repeated at one year of age, followed by annual revaccination. Foals born to vaccinated mares, should receive the first dose no earlier than 6 months of age, followed by a second dose 1 month after the first, a third dose at 1 year of age, followed by annual revaccination. Merial recommends that Merial® Imrab® 3 be given by either intramuscular or subcutaneous injection. Wyeth recommends that Rabvac™ 3 be administered by intramuscular injection only. Neither vaccine is labeled for use in pregnant mares. Rabies vaccine can only be sold to a licensed veterinarian.

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Section 6: Regulatory Information

Rabies is a reportable disease. If an animal is suspected of being rabid or a person thinks that their animal(s) has been exposed to rabies, it is required by law to report it. Call your nearest office of the Canadian Food Inspection Agency (CFIA), which is listed in the blue pages of the phone book. An inspector from the agency will investigate all calls.

Committee's Recommendations

1. It is recommended that all racehorses be vaccinated for rabies annually, prior to arrival at the track.
2. Be a responsible pet owner; vaccinate all cats, dogs and horses under your care for rabies.
3. Stray animals, with unknown vaccination histories, should be removed from all premises.

More Information

Rabies and Horses, Ontario Ministry of Agriculture and Food
Canadian Food Inspection Agency
Ontario Ministry of Natural Resources
OMNR Rabies Reporter

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