Equine Herpesvirus (EHV, EHV-1, EHV-4)

Equine Herpesvirus (EHV) is a viral disease of horses and other equidae. The disease can be caused by several different strains, but most commonly type 1 which causes respiratory disease, abortions, and/or neurologic disease, type 3 which causes coital exanthema, a venereal disease resulting in vesicles/pustules on the genital area of both male and female equidae, and type 4 which causes respiratory disease, especially in weanlings, but can rarely cause abortions, too. The neurologic form of type 1, also called Equine Herpesvirus Myeloencephalopathy, and the respiratory form of type 1 and type 4, called Rhinopneumonitis, are reportable in the State of Michigan. The disease is transmitted by direct contact with ill equidae via respiratory or reproductive secretions, but also can be spread indirectly via contact with people, tack, buckets, vehicles, and other items that have had contact with ill animals. The best way to prevent the disease is via vaccination. Biosecurity is also very important. Horses and other equidae entering the premises (new horses and horses returning from events) should be quarantined from resident equidae for 4 weeks. Pregnant equidae should be kept away from young equine as they are the population most likely to become ill with the respiratory form. Ill equidae should be isolated from healthy equidae and either be cared for solely by a designated caretaker or cared for after healthy horses. Individuals caring for ill animals should wear protective gloves, boots, and clothing when caring for those animals to avoid spreading the disease to other equidae. All items in contact with ill animals should be cleaned and disinfected before contact with other equidae.

Equine Herpesvirus-1 (strain 1) has been an emerging disease as of late, especially in the neurologic form. Horses with the neurologic form of the disease may develop incoordination, weakness, paralysis, recumbency, or even death. The vaccine does not protect from this form of the disease. Most recently, an outbreak of Equine Herpesvirus-1 occurred in May of 2011 stemming from horses that attending a show Utah. State and federal officials worked together to control the outbreak and prevent further spread. No horses that attended the event were known to have come to Michigan.

Suspected or confirmed cases of Equine Herpesvirus Myeloencephalopathy and Rhinopneumonitis should be reported to our office at 517-373-1077.