Equine Herpesvirus-1 (EHV-1), is a growing concern in the equine industry. This virus can live within horses for years and up to 90% of horses are infected with it by the time they are 2 years old. The virus will be dormant until various stresses can reactivate the virus and allow it to start causing disease. There are three forms of the disease: (1) reproductive (2) respiratory and (3) neurologic.
The reproductive form of EHV-1 can result in abortions or premature foaling. If this occurs the mare should be isolated from other horses and your veterinarian should test for causes. Typically these mares will recover and breed back normally.
The respiratory form of EHV-1 presents with signs that are similar for many respiratory infections. They include fever, loss of appetite, cough, nasal discharge and/or may act depressed. Horses showing these signs should be isolated form other horses and should be examined by a veterinarian and treated accordingly. Horses with respiratory EHV-1 will generally recover with supportive care, nonsteroidal antiinflammatories and occasionally antibiotics for secondary bacterial infections. Typically horses recover in a few days to weeks.
The most concerning form of the disease are horses that develop the neurologic form of EHV-1. The disease progresses rapidly with the only early sign being a fever and then rapidly progressing neurologic signs. These horses often become acutely ataxic (i.e. stumble and act drunk), act weak, head tilt, have trouble urinating and defecating, leaning against a fence or wall and sometimes lose the ability to stand. Once affected horses are unable to stand they have a guarded prognosis. As many as 30% of affected horses will die from the disease.
EHV-1 is contagious and spread by direct horse-to-horse contact via the respiratory tract through nasal secretions. It is important to know that this disease can also be spread indirectly through contact with physical objects contaminated with the virus: hands, tack, trailers, feed buckets, boots, clothing,etc. Because of this affected horses should be isolated from other horses for 21 days after their symptoms are resolved. Affected horses should not be moved as this only exposes other horses to the virus.