EHV-1 Outbreak: One New Case

After several new cases of equine herpesvirus-1 (EHV-1) were reported over the weekend, just one new confirmed case had been reported at press time. It has been two and a half weeks since the first cases in the outbreak--the point of origin is believed to be a national cutting horse competition held recently in Utah--were reported.

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.

Additionally, the USDA Animal and Plant Health Inspection Service released an updated situation report on May 26, which can be viewed online.

New Case

California--One additional case of EHV-1 was confirmed in California yesterday, according to a statement on the state's Department of Food and Agriculture's (CFDA) website. A previous statement on the CFDA's website indicated that seven horses displayed neurologic signs (two of which were euthanized), and the remainder were febrile or showed no clinical signs.

The surviving horses are located in the following counties: Glenn, Plumas, and Shasta in Northern California; Amador, Colusa, Marin, Napa, Placer, and Sacramento in North Central California; Stanislaus in Central California; Kern in South Central California; and Los Angeles and Ventura in Southern California.

No Change At Press Time

  • Alberta--8 positives (one displayed neurologic signs, three showed respiratory signs and/or a fever, and four had no clinical signs)
  • Arizona--11 positives (one euthanized after developing neurologic signs; clinical signs of other cases not reported)
  • British Columbia--0 positives
  • Colorado--9 positives (Six horses have shown neurologic signs; the remaining three have displayed respiratory signs and/or a fever)
  • Idaho--7 positives (four horses have displayed neurologic signs and three have only exhibited 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
  • South Dakota--0 positives
  • Oregon--5 positives (one euthanized with neurologic signs; four showing no clinical signs)
  • Texas--1 positive (not believed to be related to outbreak)
  • Utah--7 positives (one euthanized after becoming recumbent, or unable to rise; clinical signs of surviving horses 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, and enjoys photography in her spare time.

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