EHV-1 Outbreak: Case Counts Remain Unchanged

There were no new cases of equine herpesvirus-1 (EHV-1) reported to state and provincial animal health officials today, marking the second day in a row the number of confirmed cases remained steady. The point of origin for the related outbreak is thought to be an Ogden, Utah, cutting horse championship competition that ended a month ago.

"The vast majority of horse owners in Oregon and in the Pacific Northwest should feel free to participate in horse shows, rodeos, and other equine events as a recent outbreak of the neurological form of equine herpesvirus appears to be well contained," read a statement on the Oregon Department of Agriculture's website today. "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."

"While we appear to be out of the current episode, herpes viruses in general are common in horse populations as they are in human populations," State Veterinarian Don Hansen, DVM, said in the statement. "It's always a good idea to take steps that minimize the threat of disease. That was the case before the recent outbreak and will continue to be the case in the future."

Likewise, the Utah Department of Agriculture has encouraged horse owners in the state to participate in regularly scheduled events. The department also noted that good biosecurity practices be followed at all times in an attempt to prevent another EHV-1 outbreak.

Although it's not transmissible to humans, EHV-1 is highly contagious among horses and camelids, and it is generally passed from horse to horse via aerosol transmission (when affected animals sneeze/cough) and contact with nasal secretions. The disease can cause a variety of ailments in equines, including rhinopneumonitis (a respiratory disease usually found in young horses), abortion in broodmares, and myeloencephalopathy (EHM, the neurologic form). Myeloencephalopathy is characterized by fever, ataxia (incoordination), weakness or paralysis of the hind limbs, and incontinence.

At press time (4:00 p.m. EDT), the case counts remained the same in the following states and provinces:

  • Alberta-- 10 positives (four horses had no clinical signs but tested positive through laboratory testing, three had respiratory signs, and three displayed neurologic signs; one horse has died; however, it's unclear if that horse was neurologic or not)
  • Arizona--11 positives (one euthanized after developing neurologic signs; clinical signs of other cases not reported)
  • British Columbia--2 positives (clinical signs not reported)
  • California--21 positives (Eight displayed neurologic signs [two of which were euthanized] and 13 horses have only been febrile)
  • Colorado--9 positives (six horses have shown neurologic signs; the remaining three have displayed respiratory signs and/or a fever)
  • Idaho--8 positives (four EHV-1 positive horses have displayed neurologic signs [two were euthanized]; the rest have only displayed a fever)
  • Montana--0 positives
  • Nebraska--0 positives
  • Nevada--3 positives (two have displayed neurologic signs)
  • New Mexico--4 positives (USDA Situation Report indicates two have been euthanized; clinical signs not reported for other horses)
  • North Dakota--0 positives
  • Oklahoma--1 positive (displayed mild neurologic signs)
  • Oregon--5 positives (one euthanized with neurologic signs; four showing no clinical signs)
  • Saskatchewan--1 positive (no information about clinical signs released)
  • South Dakota--1 positive (clinical signs not reported)
  • Texas--1 positive (officials believe it is not related to the outbreak, but is an isolated case)
  • Utah--8 positives (two euthanized after becoming recumbent, or unable to rise; clinical signs associated with the other confirmed cases were not reported)
  • Washington--8 positives (four did not display clinical signs; signs associated with other cases not reported)
  • Wyoming--0 positives

About the Author

Erica Larson, News Editor

Erica Larson, news editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in three-day eventing with her OTTB, Dorado.

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