EHV-1 Cases in Oregon and Michigan

Two Oregon horses test positive for equine herpes virus with neurologic symptoms; Michigan releases quarantines on facilities.

The American Quarter Horse Journal

Oregon – May 4, 2015, Oregon Department of Agriculture

Four Oregon horses have now tested positive for equine herpes virus type-1 (EHV-1) with two of the horses showing neurological symptoms, according to the Oregon Department of Agriculture. It was confirmed last week that a Marion County horse had tested positive for EHV-1 and had developed neurological symptoms. The second horse that developed neurological symptoms resided at a stable in Polk County with about 40 other horses and was taken to the Large Animal Hospital at Oregon State University’s College of Veterinary Medicine over the weekend. The Polk County stable has been placed under quarantine and the remaining horses are being monitored by the stable manager and a veterinarian.

In addition to the Polk County stable, two Marion County farms remain under quarantine due to exposure to EHV-1. The infected horses and other horses exposed at the quarantined facilities attended an Oregon High School Equestrian Team (OHSET) meet at the Linn County Fairgrounds on April 16-19. ODA is currently investigating the potential of any additional exposures at this time. In addition, ODA is working to notify owners of horses that have been potentially exposed and has notified Oregon equine veterinarians.

EHV-1 is not transmissible to people. The virus is naturally occurring and widespread in the equine population. It is a common virus and may lie dormant for long periods of time and then re-activate during a period of stress, which can result in clinical disease. EHV-1 can cause respiratory disease, abortions in pregnant mares, neurologic disease, and in severe cases, death. The most common way for EHV-1 to spread is by direct horse-to-horse contact. The virus can also spread through contaminated equipment, clothing, and hands. Symptoms include fever, decreased coordination, nasal discharge, urine dribbling, loss of tail tone, hind limb weakness, leaning against a wall or fence to maintain balance, lethargy, and the inability to rise. While there is no cure, the symptoms of the disease may be treatable.

As a reminder, State Veterinarian Dr. Brad LeaMaster advises horse owners to practice strict biosecurity measures and hygiene if they travel to shows and competitions with their animals. Concerned owners should contact their veterinarian if they have questions.

Michigan – April 28, 2015, Michigan Department of Agriculture and Rural Development

On April 28, the Michigan Department of Agriculture and Rural Development released the Livingston County index farm where there were two equine herpes virus type-1 positive horses (one was euthanized). There were also an additional two premises, one in Ionia County and one in Saginaw County, that had no EHV-1 positive horses but had had exposure to the index horse that were released from quarantine during the week of April 19. These farms were released from quarantine because the horses at the property had not exhibited fevers or signs consistent with EHV-1 for 28 consecutive days.

There have been no new cases of EHV-1 since April 3, 2015. The number of EHV-1 cases of positive horses in Michigan has remained at four. Two positive horses mentioned above and two positive horses at a quarantined Saginaw County farm.

In an effort to assist individual horse owners whose horses were housed at the quarantined facility in Saginaw County in which two positive EHV-1 horses were confirmed, the Michigan Department of Agriculture and Rural Development allowed three horses to move to isolated locations, one each to Midland, St. Clair and Genesee Counties, during the week on April 12th 2015. The horses moved are not the EHV-1 positive horses mentioned above, but may have been exposed to EHV-1 positive horses. An isolated location has no other horses on the premises or within a quarter of a mile of the premises. The three isolated locations are also under quarantine. The reason for allowing horses to move from one premises to another while remaining under quarantine, is that horses continue to have fevers at the Saginaw facility, which restarts the 28-day count for horses that have no fevers or symptoms suggestive of EHV-1. Moving a horse to an isolated location allows that horse to be potentially removed from quarantine sooner than if it had stayed at the original farm.

This puts the total number of facilities under quarantine in Michigan due to EHV-1 at four. Horses at quarantined facilities are under quarantine until all horses have either had no fevers and/or clinical signs exhibited that are consistent with EHV-1 for 21 consecutive days and have subsequently tested negative for EHV-1 or have had no fevers and/or clinical signs exhibited that are consistent with EHV-1 for 28 consecutive days.

Use these 10 tips to protect your show horse before, during and after events from the threat of equine herpes virus type-1.