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Willamette Valley Horse Diagnosed with EHV-1 (Equine Herpes Virus) at OSU

More horses affected, one with the "'neurotropic' form of the virus that is far more likely to cause serious, sometimes permanent neurological damage," according to OSU. See the update at the end of this post.

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According to the Oregon Department of Agriculture and Oregon State University's Lois Bates Acheson Veterinary Teaching Hospital, a horse in Marion County has been diagnosed with the neurologic form of EHV-1, equine herpes virus, "a naturally occurring virus that can cause serious illness in horses when activated."

Thus far there is no indication the virus has spread. Horses from the same property as the sick horse traveled to an event at the Oregon Horse Center in Eugene and OSU recommends horses that attended the event have their temperatures monitored. According to the Oregon Department of Agriculture press release:

One Marion county horse has been hospitalized after testing positive for the neurological form of Equine Herpes Virus (EHV-1). The horse, which has been treated at Oregon State University’s College of Veterinary Medicine’s Large Animal Hospital, began showing acute neurologic signs on April 28 and was immediately referred to OSU. The positive EHV-1 diagnosis was made April 29. All horses at the Marion County property have been quarantined.

The Oregon Department of Agriculture reports there is no indication at this time that the virus has spread to other horses beyond those being quarantined. Preliminary epidemiological investigations are underway. In all, there are 20 horses at the Marion County stable. The stable owner and all horse owners have been very cooperative and supportive of the disease control actions taken.

The investigation shows that horses from the affected property have attended recent events held at the Linn County Fairgrounds in Albany on April 16-19, and the Oregon Horse Center in Eugene on April 25-26. While the risk to these horses appears to be low at this time, concerned horse owners are advised to contact their veterinarian.

The OSU vet hospital also issued a press release on the issue with facts on EHV-1. OSU says that this is not the mutated form of the virus but it can still have "serious consequences." OSU suggests checking out the American Association of Equine Practitioners for more information. 

No other horses that attended these events have shown clinical signs of EHV-1. Owners of horses that attended these events are encouraged to monitor their horses for any signs of respiratory or neurologic disease. EHV-1 is not transmissible to people.

“This is not the neurotropic or mutated form of the virus, which can really cause problems,” said John Schlipf, a large animal internal medicine specialist with the OSU College of Veterinary Medicine. “This form of EHV-1 can still have serious consequences.”

Schlipf said that clinical signs of the neurologic form of EHV-1 often begin with the hind limbs and include:

Uncoordinated, stumbling movements;

An unusual gait;

A weak tail tone;

Difficulty urinating, and dribbling of urine;

Nasal discharge, frequently accompanied by a fever.

The Oregon Department of Agriculture recommends horses that attended the Albany or Eugene events avoid contact with other horses and have their temperatures monitored twice daily. Temperatures over 101.5 degrees may indicate illness.

Horses with signs listed above should be isolated from other animals, and owners should contact their veterinarians immediately. EHV-1 can also affect alpacas and llamas, Schlipf said.

EHV-1 can cause abortions in animals, thus pregnant mares should not co-mingle with horses returning from those shows.

“Horse owners should be aware that although EHV-1 is not transmissible to humans, people can spread the virus on their hands and clothing if in contact with an infected horse,” Schlipf said.

Update from the Oregon Department of Agriculture:

Equine Herpes Virus now detected in four Oregon horses

Four Oregon horses have now tested positive for Equine Herpes Virus (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.

OSU has also weighed in on the latest cases:

More horses found with Equine Herpes Virus, including most serious form

05/05/2015 CORVALLIS, Ore. – Three more cases have been found in Oregon of horses infected with Equine Herpes Virus 1, or EHV-1, and one animal has the most serious “neurotropic” form of the virus that is far more likely to cause serious, sometimes permanent neurological damage.

An initial case of EHV-1 reported last week, and also being treated in isolation at OSU, only had the more common wild strain of the virus. That horse did show neurologic symptoms, although animals with that strain of EHV-1 more often have a disease that causes respiratory infection or abortion in pregnant mares.

Two more cases have been identified of horses with the wild strain, that are not showing signs of neurologic disease, and they are being treated at their home stables in Polk County. Both forms of EHV-1 are highly contagious to horses, but not transmissible to people.

However, a fourth case has been confirmed with the neurotropic form of EHV-1, veterinary experts say, which increases the seriousness of the current outbreak, and makes it increasingly important that horse owners in Oregon practice strong biosecurity management of their animals.

“About 80 percent of the horses who develop neurologic problems from EHV-1 have the neurotropic form of the virus,” said John Schlipf, a large animal internal medicine specialist with the OSU College of Veterinary Medicine. “It’s a significantly more serious concern. The disease can be fatal, or it can cause lasting neurologic damage that leaves the animal with a permanently reduced level of function.”

The most recent case was brought to OSU’s Lois Bates Acheson Veterinary Teaching Hospital from the Salem area. Both cases are being treated in isolation, and all OSU veterinary teaching hospital facilities are open for business as usual.

The initial case last week was in a horse housed in Marion County that had recently attended events at the Linn County Fairgrounds in Albany on April 16-19. Prior to the development of clinical signs in the initial case and institution of the quarantine, horses housed with the initial case had attended an event at the Oregon Horse Center in Eugene on April 25-26. The newest case was not at the Linn County event, Schlipf said, but had been in contact with other horses that attended.

Since there’s a 10-14 day incubation period for this virus, Schlipf said, it is possible that more horses will be found to be infected. Owners of horses that may be at risk are encouraged to monitor their animals closely for a fever and any signs of respiratory or neurologic disease.

More information about the virus and biosecurity recommendations is available online at http://bit.ly/1GNttiS

Early clinical signs of the neurologic form of EHV-1 often begin with the hind limbs and include: Uncoordinated, stumbling movements; An unusual gait; A weak tail tone; Difficulty urinating, and dribbling of urine; Nasal discharge, frequently accompanied by a fever.

The Oregon Department of Agriculture recommends that horses that attended the Albany or Eugene events avoid contact with other horses and have their temperatures monitored twice daily. Temperatures over 101.5 degrees may indicate illness.

Horses with these signs should be isolated from other animals, and owners should contact their veterinarians immediately. EHV-1 can also affect alpacas and llamas, Schlipf said. “We must reiterate the need for horse owners to practice biosecurity,”

Schlipf said. “People handling horses should wash their hands and clothing to reduce spread of a virus. Animals should not share tack, and horses that have traveled or mingled with other animals should be segregated. “All of these steps can help, and are especially important right now. It may be a while yet before we are out of the woods with this outbreak.”