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CORVALLIS, Ore. - The Veterinary Teaching Hospital at Oregon State University will not accept horses for anything but emergency services until at least Tuesday, Dec. 2, due to three diagnosed cases of equine influenza virus at the hospital.

Three horses are known to be infected with this virus, and others could be, officials say. The virus is a highly contagious respiratory disease in horses that typically is not fatal, but is a particular concern to foals and pregnant mares.

Other than equine species, the situation will not affect the care of any other small or large animals at the hospital.

The three infected horses have been placed in isolation and are being monitored for signs of disease. Officials wish to emphasize that this is equine influenza virus, not equine herpes virus-1, a more serious disease that is often confused with the influenza virus.

Equine influenza is not transferable to humans or other animal species, but can spread rapidly among horses and other equine species. It is the most common contagious respiratory pathogen of horses, and most infected horses show mild clinical signs from which they fully recover. However, young, elderly or pregnant animals are more vulnerable to viral diseases such as equine influenza, which can cause abortion in pregnant mares.

"Equine influenza virus is endemic in the U.S., and outbreak situations can occur intermittently in groups of horses," said Erica McKenzie, an internal medicine specialist at the Lois Bates Acheson Veterinary Teaching Hospital in OSU's College of Veterinary Medicine. "We've acted quickly to quarantine infected horses, so that hopefully no additional horses will become infected."

The Large Animal Internal Medicine and Surgery Services at OSU are working with the state veterinarian's office to inform veterinarians and horse owners about the disease.

The first clinical sign of influenza in horses is typically a fever, followed by cough, nasal discharge and lethargy. Horses with a rectal temperature of greater than 102.5 degrees, cough or nasal discharge should be evaluated by a veterinarian.

Infected horses can "shed" or transmit the virus for up to 10 days after incubation, although the peak of shedding occurs three to five days after infection. Horses that show signs of the disease should be isolated from other horses for 10 days after clinical signs first appear. Testing of nasal swab samples can be used to identify influenza infection in horses and to determine when horses infected with the virus are no longer a risk to others.

The influenza virus is easily killed by a variety of disinfectants, and thorough cleaning of stalls and equipment can help prevent the virus from spreading. Vaccination of horses during an outbreak in a training facility or barn can be beneficial, and should be performed in consultation with a veterinarian, since it may have implications for influenza test results.

Anyone with concerns about the health of their animals should contact their veterinarian or the Lois Bates Acheson Veterinary Teaching Hospital at OSU, at 541-737-2858 or http://vetmed.oregonstate.edu/

The OSU equine facility typically treats 5 to 15 horses at a time. All horses currently hospitalized will be monitored closely and repeatedly tested for equine influenza prior to discharge.