EHV-1 Outbreak: New Cases, New USDA Report Released

State officials reported just two new confirmed case of equine herpesvirus-1 (EHV-1) yesterday. However, new information surfaced about some of the existing cases in the outbreak, which is thought to have stemmed from a cutting horse championship competition recently held in Ogden, Utah.

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 yesterday, which can be viewed online.

New Information

At press time (4:00 p.m. EDT), state officials had reported the following updates:

Oregon--The Oregon Department of Agriculture released a statement yesterday indicating a fourth confirmed case of EHV-1, but not showing clinical signs, was reported. These four cases are located in the following counties: Clackamas (Northwest Oregon), Umatilla (Northeast Oregon), and Deschutes (Central Oregon).

Another horse was euthanized earlier this week after developing neurologic signs; veterinarians yesterday reported an EHV-1 case confirmation for this horse, bringing Oregon's confirmed total case count to five.

New Mexico--The USDA situation report noted that New Mexico currently has two confirmed cases of EHV-1 within state borders and that two other horses that tested positive for the neurologic form of the virus were euthanized (prior reports didn't include numbers). The clinical signs associated with the living EHV-1 positive horses were not reported. Four facilities remain under quarantine in the state, the report said.

Colorado--At press time there were still nine confirmed cases of EHV-1 in Colorado and 22 suspected cases. Two of the horses confirmed as having EHV-1 were euthanized after displaying severe neurologic signs.

"Six of the nine positive horses are showing neurological signs," Nick J. Striegel, DVM, MPH, assistant state veterinarian confirmed today.

Twelve facilities remain under quarantine in the following counties: Bent, in Southeast Colorado; Boulder and Larimer, in North Central Colorado; Garfield and Mesa, in Western Colorado; Gunnison, in West Central Colorado; and Morgan and Weld, in Northeast Colorado.

No Change

  • Alberta--5 positives (three displaying respiratory signs and two exhibiting no signs of illness).
  • Arizona--1 positive (euthanized with neurologic signs)
  • British Columbia--0 positives
  • California--18 positives (one neurologic horse euthanized; seven others displaying neurologic signs, and the remainder only were febrile or showed no clinical signs)
  • Idaho--6 positives (three displaying neurologic signs and three exhibiting a fever only)
  • Montana--0 positives
  • Nebraska--0 positives
  • Nevada--3 positives (two have displayed neurologic signs)
  • North Dakota--0 positives
  • Texas--0 positives
  • Utah--7 positives (one euthanized after becoming recumbent, or unable to rise; clinical signs of surviving horses were not reported)
  • Washington--7 positive (three of the seven have displayed signs of a fever only; clinical signs associated with the other positive cases were 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 eventing with her OTTB, Dorado.

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