EHV-1 Outbreak: One Additional Confirmed Case Reported

Just one additional case of equine herpesvirus-1 (EHV-1) was confirmed yesterday in the outbreak that has killed a dozen horses and sickened many more. For a month, state and provincial animal health officials have been working to control the outbreak, which is believed to stem from horses that recently attended a national championship cutting competition in Utah. As the number of new confirmed cases dwindles, many believe the outbreak has reached a state of containment.

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.

While many states and provinces haven't seen a new confirmed case in more than a week, officials still remain diligent in monitoring EHV-1 positive horses and those exposed to the virus after the outbreak began.

"While the number of confirmed EHV-1 cases (in Colorado) has not increased in over a week, you must all still be vigilant in caring for your horses," state Commissioner of Agriculture John T. Salazar said in a statement on the Colorado Department of Agriculture website. "Please remember to practice disease prevention within your own barns; the spread of EHV-1 is a reminder to all horse owners that disease prevention practices should be practiced as a habit and not just during times of a disease spread."

New Case

California--The lone case of EHV-1 reported in the last 24 hours is located in Glenn County, California. A statement on the state's Department of Food and Agriculture (CDFA) website indicated that the newly confirmed EHV-1 positive horse is residing on the same premises at which the last three confirmed cases in the state make their home.

According to the CDFA, two confirmed positive (EHV-1) horses were euthanized after showing severe neurological signs; eight confirmed cases displayed neurologic signs; thirteen EHV-1 positive horses displayed only a fever; and one confirmed case displayed only a nasal discharge.

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

No Change

As of press time (4:00 p.m. EDT), the following states and provinces had not reported any new confirmed cases of EHV-1:

  • Arizona--14 positives (one euthanized; no clinical signs reported for surviving horses)
  • 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.)
  • British Columbia--2 positives (clinical signs not reported)
  • 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 in a racing Quarter Horse)
  • 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

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