Q: Do I need to vaccinate my horse for Rabies?

There has been a confirmed case of Rabies in Cass County in a horse.

Rabies is an infrequently encountered neurologic disease of equids.  While the incidence of rabies in horses is low, the disease is invariably fatal and has considerable public health significance.  It is recommended that rabies vaccine be a core vaccine for all equids.

Exposure occurs through the bite of an infected (rabid) animal, typically a wildlife source such as raccoon, fox, skunk, or bat. Bites to horses occur most often on the muzzle, face, and lower limbs. The virus migrates via nerves to the brain where it initiates rapidly progressive, invariably fatal encephalitis.

Vaccines:

Three vaccines are licensed for rabies prophylaxis in horses. All are inactivated tissue culture derived products. The vaccines are given by intramuscular injection and appear to be safe. Rabies is an excellent immunogen and these vaccines induce a strong serologic response after a single dose.

Challenge studies demonstrating efficacy are required for licensing of all rabies vaccines (including those labeled for use in equids in the USA), however published results are not available. The challenge studies are conducted by the vaccine manufacturers as outlined in the Code of Federal Regulations (CFR) from the United States Department of Agriculture.

Vaccination Schedules:

Adult horses previously vaccinated against rabies:  Annual revaccination.

Adult horses previously unvaccinated against rabies or having unknown vaccinal history:  Administer a single primary dose. Revaccinate annually.

Pregnant mares, previously vaccinated against rabies:  Vaccinate 4 to 6 weeks before foaling. Alternatively, veterinarians may recommend that mares be vaccinated with rabies vaccine before breeding. Duration of immunity is such that antibodies to rabies virus are maintained at sufficient levels in mares vaccinated prior to breeding as to provide passive immunity through colostrum to the foal. Administration of rabies vaccine prior to breeding of the mare reduces the number and type of vaccines given in the period prior to foaling.

Pregnant mares, previously unvaccinated or of unknown vaccinal history:  Vaccinate 4 to 6 weeks before foaling.

Foals of mares vaccinated against rabies:  Administer a primary series of 3 doses. The first dose of vaccine should be administered no earlier than 6 months of age. The second dose should be given 4 to 6 weeks later. The third dose should be given at 10 to 12 months of age. Revaccinate annually thereafter. This schedule avoids interference with antibody production in the foal due to presence of colostrum-derived antibodies.

Foals of unvaccinated mares or of unknown vaccinal history: Administer a primary series of 3 doses. The first dose of vaccine should be administered at 3 to 4 months of age. The second dose should be given 4 weeks later. The third dose should be given at 10 to 12 months of age. Revaccinate annually thereafter.

Horses exposed* to confirmed rabid animal

Horse currently vaccinated against rabies with one of the USDA-approved rabies vaccines:  Immediate revaccination by a licensed veterinarian and observation (as directed by public health officials) for 45 days for development of clinical signs of rabies.

Unvaccinated horse: Euthanatize immediately. If the owner is unwilling to have this done then horse should be closely monitored under veterinary supervision for 6 months. Public health officials may establish requirements and conditions for monitoring of exposed, unvaccinated animals.

*Rabies exposure and transmission occur only when the virus is introduced into bite wounds, into open cuts in skin, or onto mucous membranes from saliva or other potentially infectious material such as neural tissue.

(Reprinted with permission from the American Association of Equine Practicioners)