EQUINE HERPES MYELOENCEPHALOPATHY

Myeloencephalopathy is the most suitable term for describing disease o f the equine herpesvirus 1 because the clinical syndrome results from ischemic damage to the central nervous system secondary to vasculitis (rather than from direct viral infection of neurons). Equine herpes my eloencephalopathy typically causes an acute onset of hindlimb paresis. The forelimbs and cranial nerves may also be affected. Both viral inf ection of the central nervous system endothelium and immune response t o this infection are involved in the pathogenesis of equine herpes mye loencephalopathy. Although horses of any age or gender can be affected by equine herpes myeloencephalopathy, evidence suggests that pregnant or lactating mares may be more susceptible or more severely affected. A diagnosis can be based on characteristic histopathologic lesions an d immunohistochemistry. Equine herpesvirus 1 can be isolated from nasa l swabs, whole blood, and (occasionally) the central nervous system. T reatment involves corticosteroids, nonsteroidal antiinflammatory drugs , dimethyl sulfoxide, and management of complications of recumbency or bladder atony. The prognosis is related to the severity of the clinic al signs. This article discusses the history and clinical signs, epizo otiology, pathophysiology, gross and histopathologic lesions, diagnosi s, treatment, and prognosis of equine herpes myeloencephalopathy. Cons ideration is given to measures that should be taken to control the spr ead of equine herpes myeloencephalopathy during an outbreak as well as to techniques that may be used in future investigations into the epiz ootiology of the disease.