On Saturday, September 21, 2013, the Maryland Jockey Club placed a hold order on Barn 16 at the Bowie Training Center is proactive precautionary measure, although the preliminary test came up negative. The tested horse, Clonmeen Lass, was euthanized Saturday morning. The Maryland Department of Agriculture is waiting for results from a lab in Kentucky, and MJC expects to know Tuesday evening, Sept. 24 or Wednesday morning, Sept. 25.

According to an official statement by the Maryland Jockey Club, the Hold Order affects the barn that houses horses trained by Annette Eubanks, Bobby Lee Plummer and Patrick Magill.

Horses conditioned by those trainers are not allowed into or out of the barn until given clearance by the Maryland Department of Agriculture. There will be 24-hour security outside the barn. Anyone leaving the barn needs is being required to follow best management practices for bio-security, including changing clothes and disinfect feet and footwear.

According to the American Association of Equine Practitioners:

Equine herpesvirus type 1 (EHV-1) and equine herpesvirus type 4 (EHV-4) can each infect the respiratory tract, causing disease that varies in severity from sub-clinical to severe and is characterized by fever, lethargy, anorexia, nasal discharge, and cough. Infection of the respiratory tract with EHV-1 and EHV-4 typically first occurs in foals in the first weeks or months of life, but recurrent or recrudescent clinically apparent infections are seen in weanlings, yearlings, and young horses entering training, especially when horses from different sources are commingled.

Equine herpesvirus type 1 causes a sporadic paralytic neurologic disease (equine herpesvirus myeloencephalopathy-EHM) secondary to vasculitis of the spinal cord and brain.

Both EHV-1 and EHV-4 spread via aerosolized secretions from infected coughing horses, and by direct and indirect (fomite) contact with nasal secretions… Like herpesviruses in other species, these viruses establish latent infection in the majority of horses, which do not show clinical signs but may experience reactivation of infection and shedding of the virus when stressed. Those epidemiologic factors seriously compromise efforts to control these diseases and explain why outbreaks of EHV-1 or EHV-4 can occur in closed populations of horses.

Because both viruses are endemic in most equine populations, most mature horses have developed some immunity through repeated natural exposure; thus, most mature horses do not develop serious respiratory disease when they become infected but may be a source of exposure for other susceptible horses. In contrast, horses are not protected against the abortigenic or neurologic forms of the disease, even after repeated exposure, and mature horses are in fact more commonly affected by the neurologic form of the disease than are juvenile animals.

Consistent vaccination appears to reduce the frequency and severity of disease and limit the occurrence of abortion storms but unambiguously compelling evidence is lacking.

Maryland Jockey Club racing secretary Georganne Hale says the Hold Order remains in place until the situation has been rectified.