The USDA Animal and Plant Health Inspection Service released its final situation report on the equine herpesvirus-1 (EHV-1) outbreak that affected the western United States and Canada starting in mid-May. The outbreak is believed to have stemmed from horses attending a national championship cutting competition held in Utah in early May. In its most recent report the USDA indicated that disease spread had been contained.

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.

The California Department of Food and Agriculture issued a press release June 20 indicating that animal health officials believe the outbreak has been successfully contained in that state. The release indicated that California has not diagnosed a new case of EHV-1 in the past 14 days.

"It is important that the California horse owners remain vigilant as there is always risk of disease when horses of unknown health status are commingled at one location," the release continued. "Consistent, basic biosecurity practices play an important role in reducing risk of exposure to diseases such as influenza, strangles, pigeon fever, or equine herpesvirus