A private veterinarian reported to State Veterinarian Dr. Heather Hirst Dec. 15 that a horse in her care, on a separate farm from where the original equine herpesvirus case occurred, had clinical signs consistent with the neurologic form of the disease.

Hirst and Bob Moore, Delaware Department of Agriculture animal health inspector and supervisor, went to the farm and placed a hold order (stop movement) on the single barn where the case was found.

Blood/nasal swab samples were collected from the neurologic horse and another barnmate that had shared a trailer, and samples were sent to the University of Kentucky (UK) for testing.

In-depth investigations were initiated by the Delaware Department of Agriculture (DDA) and the Delaware Harness Racing Commission to trace back all movement of the horse and its barnmates.

UK reported Dec. 16 that the sick horse tested positive for equine herpesvirus (EHV-1) on blood/nasal swab. The barnmate tested negative. Blood/nasal swab samples were taken from three other barnmates that had shared equipment with the sick horse and sent to UK. Other barnmates were not considered to be at high risk for exposure and will be sampled at a later date.

A quarantine was placed Dec. 17 on the single barn only on the farm that is situated five to 10 miles from the first quarantined barn. A single barn was quarantined because adjacent barns on the premises are not considered to be at significant risk for having had contact with the horses of the quarantined barn.

To date the investigation has not found any epidemiological links between the farms, except that both animals are involved in the harness racing industry.

Hirst announced Dec. 18, that test results on the four barnmates of the second EHV-1 neurologic horse were received from the University of Kentucky. Three tested negative for the blood/nasal swab tests and one tested positive. The positive horse is not showing clinical signs of illness. The positive test was pathotyped as non-neuropathogenic EHV-1 by Kentucky.

The second horse with neurologic disease was euthanized Dec. 17. During the current EHV-1 event in Delaware, two horses have developed neurologic disease and both have been euthanized based on decisions made by the owners of the horses and their private veterinarians. No other horses in the quarantined barns have come down with neurologic disease. One horse developed a fever of short duration but tested negative on two consecutive days. All other animals to date are asymptomatic.

The barn on the second premise will remain quarantined for 21 days.