Oregon State Treating Horse for Neurotrophic EHV-1

Oregon State Treating Horse for Neurotrophic EHV-1

In many horses, fever is the only sign of EHV-1 infection, which can go undetected.

Photo: Stephanie L. Church, Editor-in-Chief

The Oregon State University (OSU) College of Veterinary Medicine announced Nov. 8 that it has diagnosed a horse with equine herpesvirus-1 (EHV-1).

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.

“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.

Health Alert: Equine Herpesvirus

Herpesvirus is highly contagious among horses and can cause a variety of ailments in equids, including rhinopneumonitis (a respiratory disease usually found in young horses), abortion in broodmares, and myeloencephalopathy (the neurologic form). In many horses, fever is the only sign of EHV-1 infection, which can go undetected.

In addition to fever, other common signs of EHV-1 infection in young horses include cough, decreased appetite, depression, and a nasal discharge. Pregnant mares typically show no signs of infection before they abort, and abortions usually occur late in gestation (around eight months), but can be earlier. Abortions can occur anywhere from two weeks to several months following infection with EHV-1.

Clinical signs consistent with neurotropic EHV-1 infection 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; and
  • Fever (rectal temperature at or above 101.5°F 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.

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