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Rabies in Horses
Horse owners should be forewarned to consider rabies vaccination for their equids.
Rabies is caused by a virus from the rhabdovirus family. It is primarily a disease of wild animals, such as raccoons, skunks, foxes, and bats.
The disease can spread from these animals to people, unvaccinated domestic pets, and livestock, including horses.
Although rabies is rare in horses, horse owners should not ignore the disease. Exposed horses are very sensitive and susceptible to rabies.
In addition, there is no effective treatment once they are infected. The disease is one hundred percent fatal to all infected animals, including humans. Vaccination of the horse prior to exposure is the best form of protection.
Rabies is a zoonotic disease. This means that the possibility of transmission from animals to humans exists. Although there are no documented cases of horse-to-human transmission, the possibility exists and no one wants to take any chance.
Rabies is typically passed in the saliva from a bite wound. The incubation varies from two to ten weeks depending on what part of the body is bitten. However, in certain cases, it may be up to fifteen months.
Clinical signs can be very variable with symptoms being both general and similar to other diseases that affect the horse’s nervous system. This makes rabies very difficult to diagnose.
Affected horses might go off feed or exhibit depression, excessive salivation, difficulty swallowing, lack of coordination, aggressive behavior, hyperexcitability, colic, convulsions or paralysis.
Death usually occurs three to five days after the onset of clinical signs, but it can also occur in less than one day.
Currently no laboratory tests are available to confirm rabies in a live animal. A postmortem test is required to give a definitive diagnosis.
Horse owners who suspect their animals are rabid should take special care in handling and confining suspect animals. Limit the number of people exposed to a potentially rabid horse.
This limits the number of people that may require rabies treatment.
Confirmed or even suspicious cases must be reported to the state veterinarian and public health officials. If a horse is suspected of being rabid, it is usually euthanized to avoid further injuries to itself, to people handling the horse, and prevent the possibility of any transmission to humans.
Also, since rabies can present in many different forms, it can easily be confused with other equine neurological diseases, such as West Nile virus, equine herpes, and equine protozoa myeloencephalitis. Therefore, any horse that dies of unexplained causes or has neurological problems should be tested for rabies.
Remember, there is no definitive test for rabies in the live animal.
Vaccines are available to prevent rabies. Horses as young as three months of age can be vaccinated with an approved equine rabies vaccine. A yearly booster is required.
Recommendations for the observation period after potential exposure is determined by veterinarians from the Michigan Department of Agriculture. Typically, unvaccinated horses are not to be vaccinated after potential exposure and need to be quarantined and observed for at least six months. Horse owners can contact their veterinarian to give boosters to exposed and previously vaccinated horses.
Depending on the area of the state, rabies vaccination may not be a priority for horse owners, but they should at least consult with their veterinarian to discuss their overall management program.
However, the southeastern and the “thumb” counties have experienced an increase in rabies, including equids. Therefore, horses residing or traveling to this area of the state should be vaccinated.
Other populations where vaccination may be recommended are those that have frequent contact with the public such as petting zoos, therapeutic riding programs, summer camps, riding stables, etc.
Certain factors can increase risk of exposure:
1. Pasturing
2. Presence of wild animals in the area
3. Presence of a known rabid animal in the area
4. Horse traveling to areas with frequent rabies cases
Although the risk for horses is not high in Michigan, horse owners should be forewarned to consider rabies vaccination when they plan their preventive health programs.
Contact:
Dr. Judy Marteniuk
Equine Extension Veterinarian
MSU College of Veterinary Medicine
(517) 353-9710
Equine Seminar Series 
Technology@CVM Volume 1, Issue 3
