The Colorado Department of Agriculture reported that a horse residing in Weld County began displaying signs of equine herpesvirus myeloencephalopathy (EHM, the neurologic form of EHV-1) after attending an event at the Colorado Horse Park from June 22-25. The horse is currently hospitalized at the CSU Veterinary Teaching Hospital with signs clinically compatible with EHM. However, testing has not yet confirmed this diagnosis.
The horse left the Colorado Horse Park prior to showing clinical signs, so the other horses at the horse park are at low risk for exposure. However, owners and attendees should monitor their horses for clinical signs and take temperatures twice daily. If horses develop fever or any neurologic signs, owners are advised to contact their veterinarian as well as show management.
The Colorado Horse Park, while not under quarantine, is working closely with the State Veterinarian’s Office and is practicing biosecurity measures.
EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.
Herpesvirus is highly contagious among horses and can cause a variety of ailments in equids, including rhinopneumonitis (a respiratory disease usually found in young horses), abortion in broodmares, and EHM.
In many horses, the first or only sign of EHV-1 infection is fever, which can go undetected. In addition to fever, other common signs of EHV-1 infection in young horses include cough, decreased appetite, depression, and a nasal discharge. Pregnant mares typically show no signs of infection before they abort, and abortions usually occur late in gestation (around eight months) but can be earlier. Abortions can occur anywhere from two weeks to several months following infection with EHV-1.
Horses with EHM usually have a fever at the onset of the disease and might show signs of a respiratory infection. A few days later, neurologic signs such as ataxia (incoordination), weakness or paralysis of the fore- and hind limbs, urine retention and dribbling, loss of tail tone, and recumbency (inability to rise) develop.
Herpesvirus is easily spread by nose-to-nose or close contact with an infectious horse; sharing contaminated equipment including bits, buckets, and towels; or clothing, hands, or equipment of people who have recently had contact with an infectious horse. Routine biosecurity measures, including hygiene and basic cleaning and disinfection practices, should be in place at all times to help prevent disease spread.
Current EHV-1 vaccines might reduce viral shedding but are not protective against the neurologic form of the disease. Implementing routine biosecurity practices is the best way to minimize viral spread, and the best method of disease control is disease prevention.