After one horse competing at a Marion County showgrounds tested positive for the Equine Herpes Virus last month, the Florida Department of Agriculture and Consumer Servicesplaced the showgorunds and several Florida farms under quarantine.
After the first case was discovered, six more horses have tested positive for the disease. It is spread through direct horse-to-horse contact or through indirect contact such as feed and water buckets, wipe rags and transportation trailers.
The disease cannot be passed to humans.
According to the American Association of Equine Practitioners, most horses infected with the virus will not have any serious medical side effects but a small number could suffer neurological damage or death.
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 epidemic abortion in mares, the birth of weak nonviable foals, or 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, by direct and indirect (fomite) contact with nasal secretions, and, in the case of EHV-1, contact with aborted fetuses, fetal fluids, and placentae associated with abortions. 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.