EHV-1 Outbreak: No New Cases Reported Today

For the first time since the onset of the widespread equine herpesvirus-1 (EHV-1) outbreak, no new cases have been reported since the last update. Animal health officials in numerous Western states and provinces have been working diligently for the past month to control the outbreak, which is believed to stem from a national cutting horse championship competition held in Ogden, Utah, in early May.

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

At press time (4:00 p.m. EDT), no new confirmed cases of EHV-1 had been reported to state or provincial animal health officials.

The Nebraska Department of Agriculture issued a press release indicating that they have removed the quarantine from the state's previously restricted farms, as more than 28 days have passed and no confirmed cases of EHV-1 have been reported. The USDA recommends quarantining horses exposed to EHV-1 for 21 to 28 days to account for the incubation period before allowing them contact with any other horses.

No Change or Updates

  • 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 eventing with her OTTB, Dorado.

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