The horse world was shaken a few weeks ago by the announcement that not one, but two Missouri horses had been diagnosed with rabies. The first, a horse from Waynesville that was in Shelbyville, TN for the Tennessee Walking Horse National Celebration, was diagnosed on September 7. The second, a horse from Callaway County, was diagnosed with rabies on September 9. An early report that the two horses had previously had direct contact and probably been infected at the same location, was later found to be unlikely. While both horses were infected through the bite of a bat, laboratory testing found that the horses were infected with 2 different strains of rabies; the Waynesville horse was bitten by a Brown bat, and the Callaway County horse was bitten by a Silver bat.

Rabies is a viral disease that is primarily transmitted via a bite, but contact with saliva or nervous tissue from a rabid animal through open wounds, the eyes or mouth can cause infection. Any mammal can be infected with the rabies virus. The only way to definitively diagnose the disease is through post-mortem examination of the brain. The most common animals diagnosed with rabies annually in Missouri are the bat and skunk. Wild animals most frequently diagnosed with rabies in other states are raccoons, foxes and coyotes.

Clinical signs of rabies are variable but most commonly involve unusual behavior. Wild animals may lose their fear of humans or domestic animals may become aggressive. Many horses will show signs of weakness, colic, lameness and/or hyper-salivation.

The amount of time between exposure, infection and clinical signs (incubation period) for the rabies virus is also variable, but averages 3 to 6 weeks in dogs and cats. In horses, the average incubation period is 2-9 weeks, but can be longer than a year. There is no treatment for rabies in animals. Once an infected animal begins to show clinical signs, there is no hope for survival. In humans, there is a post-exposure treatment protocol of one injection of immune globulin and 5 injections of the rabies vaccine given over a 28 day period. The post-exposure regimen is highly successful in preventing the disease from progressing to clinical signs.

Rabies prevention starts with avoiding animals that might be carrying the disease. This can be easier said than done for our outdoor animals. A good place to start is by taking steps to avoid attracting wild animals to your barn by not leaving pet food out in the open. Because bats are the primary animal diagnosed with rabies, any bat found that is easily approached by a human should be assumed to be rabid. If a wild animal is noted to be acting strangely, contact your local health department and animal control so the animal can be removed and possibly tested.

As with dogs and cats, there is a vaccine to protect horses against rabies. The shot must be administered by a licensed veterinarian, and should be repeated yearly. While rabies is a very serious disease, horse owners should take comfort in the fact the disease is very rare. Of the 358 cases of rabies diagnosed in Missouri since January 2000, only 4 have been horses (274 bats and 70 skunks). This statistic should not be mistaken as a suggestion that a horse owner not vaccinate their horses; vaccinated animals act as a rabies barrier between wild animals and humans. Horse owners should discuss the risk of rabies, as well as other preventable contagious diseases, with their veterinarian so a wellness program can be tailored to fit the farm’s individual needs.