Different than Dogs & Cats
Rabies in horses is different from the way the disease is expressed in dogs and cats. Horses typically develop the "dumb" form of rabies, which means they are significantly depressed rather than agitated or violent. In fact, depression is usually the first symptom, often with a low-grade fever. The horse may also begin to chew on the area where the bite originally occurred. Eating and drinking are greatly reduced.
As the disease progresses, the horse may show more signs of irritability, disorientation or panic. This will progress quickly to obvious neurological signs, usually including seizures. The horse eventually goes down and is unable to rise. Death typically occurs in a week or less.
It is important to realize that the symptoms of rabies are not specific; they're easily confused with other conditions. In the very early stages, the horse may be thought to be coming down with a respiratory virus. The neurological involvement also mimics other causes of encephalitis or may be confused with botulism, moldy corn poisoning or other toxicities.
Rabies cannot be diagnosed while the horse is alive. Any horse that develops a rapidly progressive neurological disease with behavioral changes needs to be considered a rabies suspect. Index of suspicion is lower for horses that do not show behavioral changes and continue to eat and drink well. A horse that survives for longer than seven days, or whose symptoms stabilize, also probably does not have rabies.
There is no cure or treatment for rabies. Because of the human health risk, any unvaccinated horse that dies after a short and rapidly progressive neurological disease should be tested for rabies. This is done by submitting the horse's brain to your state veterinary laboratory for testing.
From Horse to Human
A horse with rabies is not likely to attack and bite you, but because one of the early symptoms is difficulty with eating and drinking, a problem in the mouth might be suspected, resulting in an oral examination. Virus in the horse's saliva can enter your body through even tiny surface cuts or scrapes on your skin. Never put your hand in the mouth of a horse that might have rabies.
If your vet thinks an oral exam is necessary, he or she can do it using protective gloves. The virus can also be present in any of the horse's secretions, including urine and possibly the blood. There are human cases on record where people developed rabies after receiving an organ transplant from someone who had the disease.
Vaccination
The Imrab 3 vaccine from Merial is the only product approved for use in horses. Because studies in horses are limited, it is currently recommended that all horses be vaccinated annually. However, some vets and owners choose to let their decision about vaccination be guided by testing rabies antibody titers. The Rabies Laboratory at Kansas Status University does this testing. The website is:
www.vet.ksu.edu/depts/dmp/service/rabies/index.htm. For information, call 785-532-4483.
A minimum titer of 0.5 I.U./ml is the standard set by most rabies-free countries for horses being imported, but the KSU Rabies Lab points out that studies to determine what is truly a protective titer (level that guarantees against infection) have not been done.
