South Dakota has confirmed its first case of equine herpesvirus-1 (EHV-1), a highly contagious disease that can be fatal to horses. State Veterinarian Dr. Mendel Miller said the case was identified in Hyde County on Nov. 21, with the infected horse showing neurological symptoms.
EHV-1 is not a threat to humans or other livestock, but it can cause respiratory illness, stillbirths in pregnant mares, and the serious neurological condition equine herpes myeloencephalopathy. Signs include staggering, loss of tail control, urine dribbling, and difficulty rising. Horses may also carry the virus without showing symptoms.
Officials urge horse owners to monitor animals closely, avoid unnecessary travel, and isolate horses with fevers or known exposure. The Animal Industry Board recommends PCR testing for horses with temperatures above 102.5°F. Several stables and arenas in the Black Hills have restricted horse movement, and the Custer County Fairgrounds has closed equine events through Dec. 1.
The outbreak is linked to major barrel racing events in Texas and Oklahoma earlier this month, where horses from about 30 states competed. As of Nov. 25, the Equine Disease Communication Center reported 33 cases across eight states, with Texas hardest hit.
Precautionary closures have extended to the Central States Fairgrounds in Rapid City and the Central Wyoming Fairgrounds in Casper. Organizers of the Black Hills Stock Show and Rodeo, scheduled for Jan. 30–Feb. 7, 2026, are monitoring the situation closely, noting the event’s significant economic impact on the region.
Miller emphasized vigilance: “Early detection is so important. The earlier it’s caught, the earlier treatment can be started.”
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