Equine Herpes Virus type 1

Equine Herpes Virus (EHV-1) infection in horses can cause respiratory disease, abortion in mares, neonatal foal death, and/or neurologic disease. The neurologic form of EHV-1 is called Equine Herpes Virus Myeloencephalopathy (EHM). The virus can spread through the air, contaminated equipment, clothing and hands. EHV-1 is endemic to the United States and is usually handled by the States involved; USDA becomes involved in cases involving multiple States or movement of horses across State lines.

2011 Incident Information

State and Federal Resources Allocated in Response to the Ogden, Utah EHV-1 Disease Outbreak (pdf)

Several horses that competed in the National Cutting Horse Association Western National Championship in Ogden, Utah, on April 29-May 8, 2011, were diagnosed with EHV-1. Following that event, reports were received about affected horses from multiple States and Western Canada, with several fatalities. Weekly situation reports were provided by APHIS VS from May 19 through June 23, 2011. A total of 90 confirmed EHV-1 or EHM cases were reported in 10 States (AZ, DA, CO, ID, NM, NV, OK, OR, UT, and WA). The total confirmed cases and fatalities as of June 22, 2011 are shown in the table below.

# EHV-1 Confirmed Cases
# EHM Confirmed Cases
# Dead or Euthanized Suspect or Confirmed Cases
Primary Exposed Horses (at Ogden, UT event)
Secondary and Tertiary Exposed Horses

EHV-1 Reports and Information

Additional EHM / EHV-1 Resources

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