Suspected cases of equine herpesvirus (EHV-1) have caused the Maryland State Veterinarian to place an "Investigational Animal Hold Order" on a private farm in Kent County, Md., located near the state's Eastern Shore.The farm is used as an off-track training facility for a Pimlico-based trainer. The farm received a horse from Pimlico Jan. 10 before track officials closed movement to and from the facility. The Maryland Department of Agriculture is waiting for test results, which are expected next week, to determine the cause of illness for one horse euthanized Thursday morning and another showing neurologic signs. "This new occurrence is extremely unfortunate and we are working closely with everyone involved and using the best science available in the equine research community to prevent any possible spread of illness," said Maryland State Veterinarian Guy Hohenhaus. "It is believed that this incident is not a distinctly new case. We encourage horse owners with concerns to contact their private veterinarian to determine if a vaccination or booster is recommended for their horses at this time." Equine herpesvirus-1 (also known as "rhino"), which causes upper respiratory infection, can also cause neurological signs. Among the first signs of the illness are unexplained fever and mild-to-severe ataxia or unsteady balance. There is currently no known method to reliably prevent the neurologic form of EHV-1 infection. It is recommended to maintain appropriate vaccination procedures in an attempt to reduce the incidence of the respiratory form of EHV-1 infection, which may help prevent the neurologic form. Transmission of the virus can occur via coughing or sneezing, as well as by direct contact with infected horses, feed, and equipment. There is no reason to believe that there is any human health risk. The name and location of the farm will not be released, as it is a private farm. The owners and management are aware of what activities have taken place on the farm and are fully cooperating with officials to prevent the possibility of spread. Private veterinarians with questions or horses with signs they believe may be consistent with equine herpesvirus are asked to call the Maryland Department of Agriculture Animal Health office during business hours at 410-841-5810. Updates will be posted daily on the MDA Website.