CORVALLIS, Ore. – The Oregon State University College of Veterinary Medicine has diagnosed a horse with a form of equine herpes virus, a naturally occurring virus that can cause serious illness in horses.
The horse is being treated for the neurotropic form of the virus, which is a mutated type of EHV-1 with a higher likelihood of causing neurologic disease.
The horse in question is from the Coos Bay, Oregon, area and became acutely affected with weakness and staggering on Nov. 4.
The animal is isolated at the Lois Bates Acheson Veterinary Teaching Hospital at the OSU College of Veterinary Medicine in Corvallis.
EHV-1 can cause abortion in pregnant mares, which should be kept away from horses showing signs of the disease and also kept away from horses that have been in contact with exposed animals. Although a vaccine exists for EHV-1, it does not prevent infection and is not known to prevent clinical signs of neurologic disease related to the neurotropic form.
“Horse owners should be aware that although EHV-1 is not transmissible to humans, people can spread the virus on their hands and clothing to horses, alpacas or llamas if they are in contact with an infected horse,” said Erica McKenzie, professor of large animal internal medicine at the College of Veterinary Medicine.
The college has discontinued all elective surgical and medical services for horses and camelids, such as llamas and alpacas, for at least the next two weeks to minimize the risk of spreading the virus.
Clinical signs consistent with infection with neurotropic EHV-1 often start with weakness in the hind limbs and can also include:
- Uncoordinated, stumbling movements;
- An unusual gait;
- Weak tail tone;
- Difficulty urinating, and dribbling of urine;
- Inability of geldings and stallions to retract their penises;
- Nasal discharge;
- Fever (rectal temperature at or above 101.5 degrees Fahrenheit in resting horses).
Horses with any of the signs listed above should be isolated from other animals, and owners should contact their veterinarians immediately.
In rare cases, EHV-1 can cause blindness and central nervous system damage in alpacas and llamas.
Additional information regarding equine herpes virus and biosecurity recommendations are available from the American Association of Equine Practitioners at https://aaep.org/guidelines/infectious-disease-control/equine-herpesvirus-resources.