ANDERSON, Ind. — West Nile virus cases are rising in humans and horses this year. Just as people must take precautions against the virus, horse owners should take steps to protect their animals.
Dr. Tracy Norman recommends vaccinating horses against the disease and taking measures to prevent mosquito bites. Norman is clinical assistant professor at the Texas A&M College of Veterinary Medicine & Biomedical Sciences Large Animal Clinic.
Mosquitoes transmit the virus from avian hosts to humans and horses, which are considered “dead-end” hosts of West Nile because the virus is not contagious among them. In those bitten by an infected mosquito, the virus can multiply in the blood system, cross the blood brain barrier and infect the brain. There, it can cause inflammation, interfering with central nervous system functions.
Most infected horses do not show signs of the disease. (Most humans don't either, for that matter.) In horses that do show signs of the virus, symptoms are similar to other neurological diseases. They can include impairment of basic motor skills - including loss of coordination or asymmetrical weakness - a change in behavior or drowsiness. Horses with West Nile may have a fever early in the disease and show sensitivity to touch and sound, as well as twitching in the face, muzzle and neck.
“These typical neurological signs are not always present in infected horses. Sometimes infected horses just appear colicky,” said Norman. “You should always consult with a veterinarian if you suspect a horse of having West Nile virus. Confirmation of infection is easily diagnosed through a blood test. Then owners and the veterinarian can plan a course of treatment.”
The main treatment is supportive care. Anti-inflammatory drugs - such as Banamine, steroids and dimethyl sulfoxide - and intravenous fluids are often used. A sling can be used to support a horse that is having trouble balancing as it recovers.