Rabies is a rapidly fatal brain disease that horses usually acquire after being bitten by an infected animal (bat, skunk, raccoon, coyote, fox, wolf, dog). Signs of this disease can vary widely. The disease can only be definitively diagnosed after death. Even a sign as unlikely as a mysterious lameness can result from a rabies infection.

Signs of rabies can be divided into a "furious/mad dog" form and a "paralytic/dumb" form. The furious form is the classic fearless, aggressive attitude popularized in the media (rolling, biting, striking). In the paralytic form, a horse may have difficulty swallowing or salivate excessively.

Horses that are suffering from severe undiagnosed brain disease that have signs compatible with this disease may need to be euthanized and rabies diagnostics run immediately.

Rabies is a zoonotic disease, meaning that it can be transferred from an infected horse to humans. It is one of the few equine diseases that is easily transmitted from an infected horse to humans. It is nearly 100% fatal in horses and people. For this reason, always take care to avoid human exposure if you suspect that your horse has this disease. ALWAYS wear latex gloves when handling horse's mouths because exposure to humans is generally through the virus-infected saliva.

Theoretically, the virus needs to gain exposure to the human bloodstream through a cut or open wound, but in reality that might not be required. If you have been exposed to a horse with (or suspected of having) rabies you should contact your doctor immediately.

Rabies is a reportable disease, meaning that if a horse has or is suspected of having this disease, vets are required to report it to agricultural authorities (usually the State Veterinarian). These authorities may investigate the case as part of a larger effort to monitor equine health and coordinate with other States and the USDA APHIS in preventing the spread of illness or disease on a national and international level.