An Illinois boarding stable remains quarantined after eight horses tested positive for the equine herpes virus (EHV-1). Two infected horses have been euthanized at Kane County’s Sunset Hill Farm.
EHV-1 is not a reportable disease in Illinois, so veterinarians are not required to report new cases to the state.
The incubation period of EHV-1 is 1-10 days and signs are typically seen within 1-3 days. Viral shedding of the virus occurs for 7-10 days, but can occur up to 28 days from the onset of signs.
Symptoms may include fever, decreased coordination, nasal discharge, urine dribbling, loss of tail tone, hind limb weakness, leaning against a wall or fence to maintain balance, lethargy, and the inability to rise. While there is no cure, the symptoms of the disease may be treatable.
No horses have left the farm since September, and no new ones have come in, but the virus can be spread through various methods. Direct, horse-to-horse contact is a common route of transmission.
Indirect transmission happens when infectious materials are carried between infected and non-infected horses by people or inanimate objects such as buckets, tack, or trailers. Aerosol transmission can also occur when infectious droplets are inhaled. The source of infectious droplets is most often respiratory secretions.
EHV-1 may lie dormant for long periods of time and then re-activate during a horse’s period of stress, which can result in clinical disease.
Since the beginning of the year, cases of the virus have been diagnosed in California, New Mexico, Arizona, and Illinois. Pennsylvania also saw cases of EHV at the end of 2015.