Virus alert: Saddlebred in California, British Show Horse, and a Herd of Wild Utah Burros Latest Equine Herpes Virus Victims

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Virus season is upon us. It opens with two unusual cases in California, in that the affected horses are Saddlebreds. There is also news from the United Kingdom about an EHV case euthanized there, as well, and from Utah comes news that a herd of wild burros have died after showing signs of what is, so far, an unidentified respiratory-type disease.

Equine Herpes Virus is usually quiet in the summer, even with the mixing of so many horses at shows and on the trail. Cases usually start to be reported in the fall through winter, and it is not uncommon for the virus to close stable areas at racetracks or horse shows.

True to form, three situations involving what is believed to be a form of Equine Herpes Virus caused the death of horses in three farflung locations in the United States and abroad in the past week. It's important to check horses' vaccination records, and make sure that a biosecurity plan is in place for horses coming and going from shows and races or breeding sessions, or moving in as new residents.

Horse owners in California will want to be aware of an official warning about the first-of-fall small but deadly outbreak of Equine Herpes Virus in that state.

The California incident was announced on November 3, by the California Department of Food and Agriculture (CDFA) Animal Health and Food Safety Services, Animal Health Branch in Sacramento. It was also posted on social media by the Equine Disease Communication Center.

CDFA provided this news capsule:
“On November 3, 2016, a five-year-old Saddlebred displaying severe neurologic signs and a ten-year-old Saddlebred in Los Angeles County displaying moderate neurologic signs were confirmed positive for the non-neuropathogenic strain Equine Herpesvirus-1 at the California Animal Health and Food Safety Laboratory. 

“Due to severity of clinical signs, the 5 year-old horse was euthanized on (the same day) November 3, 2016. The Department has issued a quarantine for exposed horses at the facility and has implemented enhanced biosecurity measures. All exposed horses will have temperatures taken twice daily and be observed for clinical signs compatible with EHV.

“The two confirmed positive horses, along with four other horses, recently returned from a horse show in Las Vegas, Nevada from October 27 to 29, 2016. These horses returned to the California home premises on October 30. Out of an abundance of caution, show management has notified trainers/owners participating in the event to recommend twice daily temperature monitoring and observation of compatible clinical signs. 

“CDFA Animal Health Branch veterinarians are onsite monitoring the situation and will provide additional updates as they become available.”

The next day, CDFA posted this update: "Three additional horses were confirmed positive for the non-neuropathogenic strain of Equine Herpesvirus-1 on the Los Angeles County index premises. Two of the three affected horses display neurologic signs and the third horse is febrile and all three are in isolation. Two of these newly confirmed equine cases attended the Las Vegas horse show last week.

"At this time, no additional EHV-1 cases have been confirmed in horses that exhibited at the Las Vegas horse show on October 27 - 29, 2016. Exposed horses on the Los Angeles index premises continue to have their temperatures monitored twice daily and enhanced biosecurity measures remain in place. CDFA Animal Health Branch veterinarians continue to monitor the quarantine and situation on-site and will provide additional updates as they become available."

On November 5th and 6th, CDFA posted assurances that there were no new cases. However, over the weekend, NBC News reported that the horses were quarantined in Barn A at the Los Angeles Equestrian Center at Griffith Park in Burbank.

United Kingdom case
In the United Kingdom, authorities and the media are working hard to remind the horse-owning public about the risks of equine herpes virus, in its varied forms, and the need for best biosecurity practices. A horse returned to its boarding stable after a local horse show and developed signs of lethargy and was unable to stand by evening, according to a report in Horse and Hound. The horse was transferred to the nearby Royal Veterinary College isolation unit, but was euthanized.

On Monday, Horse and Hound updated its report to note that a total of four horses from that boarding stable had been euthanized, with two additional horses being supported for showing symptoms of the disease.

Other horses at the stable, and horses that attended the show, are being monitored for early signs of the virus but none have been reported so far. Equine herpes virus is not as common in Great Britain as it is in the United States.

25 Dead Burros in Utah
A third story is being reported by local newspapers in the western United States, although we don’t yet have a source document to back it up. This report, originally published in the Sanpete Register in Utah, describes the death of 25 wild burros in an off-range containment in Extell, Utah. According to the paper, the BLM suggests that the cause of the burros’ death may have the relatively rare asinine herpes virus (AHV). The burros were tested for Equine Herpes Virus and Equine Influenza, without positive results, according to the news reports, and the BLM is pursuing DNA testing for asinine herpes virus. AHV also may affect horses.

As this article proves, Equine Herpes Virus comes in many forms, touches many types of horses, and no longer pays attention to the calendar. EHV may affect horses any time of the year and while it is of paramount importance to practice good biosecurity and prevent infection, this is a virus that has many cards up its sleeve. 

Try to protect your horse and learn as much as you can about the new forms of the disease and why it can be so unpredictable. Make sure that your reference material on EHV is updated, and only rely on website references with a publication date in the last year or two. If a reference does not have a date and a primary source such as the AAEP, a university vet school or a state or federal animal health agency, find a different resource.

Reader resources for this article:

CDFA Equine Health Alert, November 3

What the horse owner should know about Equine Herpes Virus-1 (Michigan State University Veterinary Extension document, published in 2015)

Horse and HoundHorse put down in equine herpes ‘outbreak’

San Pete Messenger:Dead burros in Axtell contracted rare virus

An interesting reference paper abstract (paywall to view full paper):

Prevalence of asinine herpesvirus type 5 (AsHV-5) infection in clinically normal Lipizzaner horses
James Oliver Rushton, Jolanta Kolodziejek, Barbara Nell, Norbert Nowotny, 
The Veterinary Journal, Volume 200, Issue 1, April 2014, Pages 200-203, ISSN 1090-0233,
http://dx.doi.org/10.1016/j.tvjl.2013.10.035.