Four horses stabled in Allegheny County, Pa., have been euthanized after developing neurologic signs consistent with equine herpesvirus-1 (EHV-1), according to a statement circulated by the Animal Health Emergency Management and Information Network on behalf of the Pennsylvania Department of Agriculture Bureau of Animal Health and Diagnostic Services. Three of the euthanized horses tested positive for EHV-1. A fifth horse has since developed signs of the disease.

The four barns on the premises house 117 horses. All of the affected horses were stabled in one barn.

An official quarantine of the entire premises was put into place July 20 by the Pennsylvania Department of Agriculture. The quarantine will remain in effect from 21 days after the resolution of clinical signs and all horses test negative for neurologic EHV-1.

Officials are tracing all horses that were in contact with horses from this facility starting July 7