Neuropathological study of gazelle herpesvirus 1 (equine herpesvirus 9) infection in Thomson's gazelles (Gazella thomsoni).

Gazelle herpesvirus (GHV-1), correctly designated as equine herpesvirus 9, is a new type of equine herpesvirus immunologically related to equine herpesvirus 1 (EHV-1). As a sequel to a virological study, the neuropathology of encephalitis caused by GHV-1 in Thomson's gazelles (Gazella thomsoni) was examined. Seven gazelles died with or without neurological symptoms between early September and mid-October in 1993. No gross abnormalities were observed at necropsy, but all animals had non-suppurative encephalitis, characterized by necrosis and degeneration of neurons, glial reactions and perivascular cuffing in the cerebrum. Five cases showed intranuclear inclusion bodies, with the appearance of herpesvirus in the degenerating neurons. Immunohistochemically, all seven animals showed a positive reaction to EHV-1 antigen in neurons in the necrotic areas of the cortex. The clinical course and morphological features of GHV-1 encephalitis were distinct from those of EHV-1-induced encephalitis in the horse, which is characterized by vasculitis, thrombosis, ischaemia, and lack of intranuclear inclusions in neurons.