EHV-1 Confirmed In WY

Posted in: Featured, Horse Care, Ranch Life, Rodeo

Unfortunately, last week there were reports coming from Campbell County in Wyoming that there was a confirmed case of EHV-1.

So what is EHV-1? Accordng to Wikipedia-Equine herpesvirus 1 (EHV-1) is a virus of the family Herpesviridae that causes abortion, respiratory disease and occasionally neonatal mortality in horses. Initial spread of EHV-1 by a newly introduced horse through direct and indirect contact can lead to abortion and perinatal infection in up to 70 percent of a previously unexposed herd. Abortion usually occurs in the last four months of gestation, two to four weeks after infection of the mare. Perinatal (around the time of birth) infection can lead to pneumonia and death. Encephalitis can occur in affected animals, leading to ataxia, paralysis, and death. There is a vaccine available (ATCvet codeQI05AA11 (WHO)), however its efficacy is questionable.The virus varies in severity from sub-clinical to very severe. Most horses have been infected with EHV-1 but the virus can become latent and show no signs and never be an issue. In 2006, an outbreak of EHV-1 among stables in Florida resulted in the institution of various quarantine measures. The outbreak was determined to have originated with several horses imported from Europe via New York, and then shipped to Florida.


The report that came out from is as follows –

February 06, 2018
Equine Herpes Viruses
Campbell County, WY
Confirmed Case(s): No Quarantine

Source: Wyoming Department of Agriculture

“The Office of the Wyoming State Veterinarian confirmed a case of Equine Herpesvirus Myeloencephalopathy (EHM) at a private facility in Campbell County, Wyoming. On January 30, 2018 a 6-year-old QH gelding of unknown vaccination status at a private facility had rapid progression of hind leg ataxia, weakness, recumbency and normal cranial nerve response. The Wyoming Livestock Board was informed on Friday 2/3/18 of a horse in the Gillette area seen by a practitioner for rapidly progressive neurologic signs which upon referral was ultimately euthanized and transported to Colorado State University for necropsy.  Nasal swabs taken before euthanasia were positive on PCR for EHV-1 wild type.  On 2/5/18,  a second horse in the Gillette area seen by another practitioner was reported as having a sudden onset of neurologic signs and is currently being treated and held in isolation at the veterinary facility. Results from nasal swabs and blood samples are pending from the Wyoming State Veterinary Laboratory. Horses stabled at the premise where the positive horses originated are being monitored with temperatures taken twice daily and recorded. Self-imposed quarantines at the recommendation of the Livestock Board are in place pending final necropsy report and test results respectively. Both of the positive horses had competed at the Cam-Plex in Gillette within the past three weeks, though neither had been stabled at the facility. There are no known affected horses at the Cam-Plex which will be instituting enhanced biosecurity measures and public awareness as well as releasing a precautionary statement to the public and those that may have been potentially exposed.”

Info about this has just started showing up on social media. I saw this post on Yellowstone Equine Hospital Facebook page. It covers the subject well. –


Dear Friends and Clients:

As you may have heard, we are experiencing an outbreak of neuropathic equine herpes virus in our practice area. Sadly, one of our Gillette clients lost a very nice horse last week, just days after competing in a barrel race at the Gillette Cam-Plex.

Equine herpes virus EHV-1 and very rarely, EHV-4 are the causes of Equine Herpesvirus Myeloencephalopathy (EHM). EHV-1 is easily spread from horse to horse through contact with nasal discharge or spread in aerosol droplets. Horses can also contract the virus by coming into contact with contaminated surfaces such as stalls, trailers, water, feed and tack. Humans can spread the virus from horse to horse by contaminated hands and clothing.

The incubation period of EHV-1 ranges from 2-10 days. Horses can shed the virus during the incubation period. Infected horses can shed the virus even without showing clinical signs.

Horses infected with EHV-1 typically develop a biphasic (two phase) fever, most often on day 1 or 2, then again on day 6 or 7. Some horses do not develop a fever. Neurologic signs may not develop until the second fever. Once horses develop a fever, we recommend immediate testing via nasal swab. The risk of shedding the virus in these horses is extremely high.


Fever (biphasic), nasal discharge, depression, incoordination, hind limb weakness, loss of tail tone, urine dribbling or inability to urinate, dog sitting position, leaning into a wall or fence, or inability to rise.

Treatment includes aggressive supportive care. In addition, we recommend the use of the anti-viral drug Valacyclovir, and the anti-clotting drug heparin in all cases. Once a horse develops severe neurologic signs, the prognosis becomes much worse. The key to successful treatment is recognition of early signs and aggressive, prompt treatment.

None of the current USDA approved vaccinations are proven to prevent the neuropathic form of EHV-1. Because the disease is shed via the respiratory route, we always recommend that you maintain current EHV-1 vaccines on all horses at all times and follow biosecurity measures if your horses are at risk for EHM.

Please do not hesitate to contact me directly if you have any questions about this life-threatening disease. Our office number is 307-527-6968.

Best regards, Dr.V”

I feel so bad for the young cowgirl who lost her horse this week. Her horse had been vaccinated, but this virus is hard to combat against. The horse contacted it at a barrel race that had people there from several different states… so it is hard to know where it came from.

Posted in: Featured, Horse Care, Ranch Life, Rodeo

About Tiffany Schwenke

My family has been ranching and raising horses for over 100 years. We raise, train, and market AQHA horses at North Four Mile Creek Horse Ranch. We produce the annual event WYO WILD RIDE RANCH RODEO. I am a wife and a mother to 3 amazing...

View all posts by Tiffany Schwenke