The New Jersey Department of Agriculture has quarantined a Warren County farm after a 22-year-old horse was diagnosed with the highly infectious equine herpes myeloencephalopathy (EHM), the often deadly neurologic form of equine herpesvirus-1 (EHV-1). The horse had not left the premises in years.

The Thoroughbred mare was euthanized March 31 after she exhibited a rapid progression of neurologic signs typical of EHM; she was subsequently tested positive for EHV-1. There are a number of other horses present at the facility, none of which have shown signs of the disease.

This is the third case of EHM in New Jersey this year. An EHM-positive horse in Somerset County prompted quarantines at two farms in January, and two other farms were quarantined in February due to a sick horse in Gloucester County. No other horses in the two unrelated cases showed signs of the illness and the quarantines were lifted after 21 days of quarantine.

“The department took swift action to prevent the disease from spreading to other horses by enacting a quarantine, which stops movement of horses in and out of the farm and puts in place preventive measures to contain the virus,” said New Jersey Secretary of Agriculture Douglas H