Isolated Equine Herpes Virus in Wyoming: Original Cutting Horse Outbreak Winding Down

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It’s a new horse world. This video from Parelli Natural Horsemanship is an example of the new awareness being exhibited by horse event and show organizers across the country. New regulations for entering showgrounds are being written, and facilities where horse owners bring their own horses are reassuring their guests that precautions are taken to keep horse stabling areas sanitary.

It’s not over until it’s over, but the flurry of news about Equine Herpes Virus in the western states is slowing to a trickle. Much of the news is about the re-opening of facilities and the re-scheduling of events that had been canceled.

A report from Wyoming of a new case is the latest story in this outbreak, which is now six weeks old. However, the Wyoming case is not believed to be related to the original group of cutting horses that were present at an event in Utah and then dispersed throughout the west, taking the virus with them. A much larger outbreak was averted by isolating many of the horses that competed in Utah.

Note: To stay in touch with the data on horses involved in the original outbreak, you’ll need to monitor the USDA’s reports. Information is compiled on the latest US Department of Agriculture cumulative report on EHV cases in western states, and on the EQUUS CANADA web site for horses in Canadian provinces. State reports are now few and far between.

Here’s some EHV news from around the West:


Several sources have quoted an Arizona newspaper, The Sierra Vista Herald, which in turn quoted an Arizona veterinarian, Dr. Dusti Prentice, as stating that there were two new cases in Arizona, but there has been no report from state officials. These reports are frustrating to track down, and you can find several of them on the internet.


On June 20, the State of California Department of Food and Agriculture issued this statement:

“The recent disease outbreak of the neuropathogenic strain of Equine Herpes Virus -1 (EHV-1) associated with the horses that attended the National Cutting Horse Associations Western National Championships in Ogden, UT is contained. Containment is based on the fact that California has gone more than 14 days from the last clinical case onset date without a confirmed clinical case of EHV-1.” “I want to thank California’s horse owners and veterinarians for their prompt and thorough actions to isolate and monitor exposed animals and contain this outbreak of EHV-1,” said State Veterinarian Dr. Annette Whiteford. “We also owe the success of this project in part to the outstanding isolation biosecurity measures implemented by horse facility managers, show/event managers and other professionals who work with and care for horses.”


On June 22, the Colorado Department of Agriculture’s State Veterinarian’s office released a number of quarantine and hold orders associated with the recent spread of Equine Herpesvirus (EHV-1) in the state; according to the State Veterinarian’s report, the disease is considered contained within Colorado. No new cases have been confirmed since May 20, 2011.

“I’m proud of the coordinated effort by the horse industry, veterinarians, event coordinators, and our office. Without the proactive collaboration of all involved, this disease could have had an even greater negative impact on Colorado’s horse industry,” said State Veterinarian, Dr. Keith Roehr in an official statement.


The state of Idaho’s latest statement as of June 10: “There have been no new cases of suspected or confirmed EHV-1 infection in Idaho horses reported to the Idaho State Veterinarian during the past 8 days. Previously confirmed positive horses will remain under veterinary care and monitoring until the appropriate quarantine period has passed.”


On June 11, the Montana Department of Livestock reported that a clinically healthy horse in Gallatin County tested positive for Equine Herpes Virus (EHV-1). “We have a non-clinical EHV-1 positive case associated with the National Cutting Horse Association (NCHA) Western National Championships in Ogden, Utah, April 30-May 8, 2011,” said Dr. Marty Zaluski, state veterinarian. “Fortunately, this horse not only remains healthy, but has been separated from other horses since returning from Ogden.


On June 3, Nebraska State Veterinarian Dennis Hughes released the horse premises that were quarantined by the state in May after several cases of Equine Herpesvirus (EHV-1) were confirmed across the nation. These premises were housing horses that had returned to Nebraska from the cutting horse event in Utah that was the origin of the outbreak in other states.


On June 8, the state issued a statement saying, “Since May 16th, 2011 the Department of Agriculture received laboratory confirmation of EHV-1 infection for a total of 3 horses (2 in Washoe Co, 1 in Elko Co).” Dr. Phil LaRussa, State Veterinarian and Administrator, Nevada Department of Agriculture has issued a statement that: ?”The only horses that are currently still under movement restrictions in Nevada are those horses that either attended the Ogden, UT event in early May or were exposed to Ogden attendees and subsequently developed disease.”

According to a press release, all clinically healthy horses, regardless of their exposure status, are free to move “in state and interstate”. Horse owners should feel free to attend shows and exhibitions, rodeos and cutting events, the release advised.

New Mexico

New Mexico hasn’t updated its advisory status since May 31.

North Dakota

North Dakota hasn’t offered any updated information.


Oklahoma has no recent official updates. The National Reining Horse Association (NRHA) has announced some updates to its showgrounds entry procedure and requirements for horses attending the 2011 NRHA Derby, which opens this weekend, which open this weekend at the Oklahoma State Fairgrounds.


State Veterinarian Dr. Don Hansen of the Oregon Department of Agriculture says sufficient time has passed for most horses that may have been exposed to the virus traced to a horse show in Utah last month. The few horses that have shown symptoms of the disease will remain quarantined in their barns or stalls and monitored closely until it is clear the virus is no longer present. In total, 20 horses from Oregon attended the cutting horse show in Utah that was the source of the outbreak; five tested positive for the virus, and one died.

“Any horse that hasn’t tested positive, shown any symptoms, or not exposed to a confirmed positive horse should be okay for travel and participation in equine events,” says Hansen. “We’ve been in close contact with owners of the affected horses and their stable mates. Those animals have been kept isolated and under close watch for the past few weeks. If these horses have gone 28 days without any signs of illness, including fever, they are most likely no longer contagious and can be considered for quarantine release.”

Regarding horse activities in the state, Hansen said, “The threat of a herpes virus reappearing is no different than it was before the show in Ogden, Utah where the recent outbreak originated. Horse owners should feel confident about taking their animals to shows and exhibits this summer. But they should also understand there has always been a moderate risk of exposing their horses to a herpes virus anytime they go to a show. What happened in Ogden hasn’t made that risk any higher. There are thousands of horse events all summer long in the US and we only see one or two outbreaks of the herpes virus in a whole season. People should keep that perspective as they plan activities with their horses.”

South Dakota

South Dakota had reported one horse with EHV, not associated with the cutting horse event in Utah, on May 20. The state has not issued an update since then.


Friday, June 10 was the date that Texas was expecting to lift movement restrictions on the last nine of the 26 horses in Texas that attended the National Cutting Horse Association (NCHA) Western National Championships event held in Ogden, Utah, April 30-May 8.

While Texas is on record as having two confirmed cases, one is a New Mexico horse that sought treatment at a Texas veterinary hospital and has since returned to its state of origin. The second case is a Quarter horse racehorse that is unrelated to the cutting horse group.

“Sufficient time has passed for most horses that may have been exposed to the virus traced to the cutting event held in Ogden, Utah, last month. Though none showed symptoms of the disease, the few horses in Texas that tested positive will remain quarantined on their premises and monitored closely until the virus shedding period has passed,” Dr. Dee Ellis, State Veterinarian, said.


A June 2nd press release from State Veterinarian Bruce King advised:

“The Utah Department of Agriculture and Food, Office of the State Veterinarian is now recommending that all equine events be held as regularly scheduled. No events to date have been cancelled by this office and we are now recommending that any and all equine events continue, as the threat of spread of EHV-1 virus at these events is now minimal.

“A horse that was exposed to horses at one of the quarantine premises has tested positive for EHV-1 after having an elevated temperature. We currently have seven (7) quarantined private locations (Box Elder, Davis, Kane, Salt Lake and Utah (3) counties) with a total of eight (8) confirmed cases and thirteen (13) suspect cases at these locations. To date, two of the Utah cases were humanely euthanized after going down and being unable to return to their feet.”

On June 15, the state of Utah said that no horses had tested positive since the end of May. Perhaps the testing date of the final case was earlier than the press release.


On June 3, the office of the Washington state veterinarian issued a statement that he believed that sufficient time had elapsed for signs of nEHV-1 to appear in horses exposed at the National Cutting Horse Association Western National Championships in Ogden, Utah, as well as their stable and pasture mates. Dr. Leonard Eldridge recommended that any horse that has not tested positive, exhibited symptoms or been exposed to a confirmed positive horse be cleared for travel. “I continue to recommend that horses that are confirmed positive for nEHV-1 or were exposed to a positive case be isolated for 28 days after all symptoms have cleared up,” said Dr. Eldridge. “While the animal may appear to have recovered, it can still transmit this highly contagious disease to another horse.”

Washington’s ninth case of EHV was confirmed at the large animal hospital at Washington State University on June 15th.


Wyoming’s state veterinarian reported a case of the neurologic form of EHV in that state yesterday (June 22), but the case was unrelated to the Utah cutting horse event. A second horse at the same premises was euthanized.




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