EHV-1 Outbreak: New Cases Trickling In

The equine herpesvirus-1 (EHV-1) outbreak that captured the attention of horse owners and animal health officials across the nation continues to see new cases diagnosed; however, the rate at which these confirmed cases are cropping up has dropped.

In a statement on the Colorado Department of Agriculture's website, State Veterinarian Keith Roehr, DVM, said, "The encouraging news for us is that we have not seen any new confirmed cases in Colorado since May 20, 2011, and we hope that trend continues. But we still cannot let down our guard as we work to mitigate and control EHV-1."

Additionally, the Colorado State University Veterinary Teaching Hospital (VTH) has reopened its doors to all patients after restricting cases to emergencies only in an attempt to squelch the spread of EHV-1.

"Our equine section is now open to all equine patients but will continue to use extra biosecurity precautions," a statement on the VTH website read. "This revises previous limitations to accept only emergency cases that were enacted as a precaution in response to the recent widespread outbreak equine herpesvirus-1. The hospital also remains open to all other animal patients."

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.

At press time (4:30 p.m. EDT), only one new case had surfaced since the last update:

South Dakota--One confirmed case of EHV-1 has been reported in South Dakota, according to the state's Animal Industry Board. A press release indicated that the horse had been quarantined; however, the clinical signs associated with the horse were not reported. The EHV-1 positive horse is located in Gregory County, which is in Southern South Dakota.

No Change:

  • 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
  • California--20 positives (two euthanized; seven reported to display neurologic signs while the remainder were febrile [feverish] or asymptomatic)
  • 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
  • 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

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.