A hamster model of equine herpesvirus 9 induced encephalitis

An acute and lethal infection of equine herpesvirus 9 (EHV-9), a new type o f equine herpesvirus, was established in Syrian hamsters by intranasal inoc ulation. Clinical symptoms included the loss of body weight, nasal and ocul ar discharges and apparent neurological symptoms. Both LD,, and ID,, were e qual at 33 plaque forming units. Histological and immunohistochemical exami nation demonstrated that the virus replicated in the olfactory mucosal cell s and in the neurons of the olfactory bulbs, cerebrum and mesencephalon. Th e induction of encephalitis by intranasal but not by other routes of inocul ation (i.v., i.p., i.m.) indicated that EHV-S entered the brain via the olf actory nerve and then spread trans-synaptically to connecting neurons along the olfactory tract. This animal model should be useful for studying the p athogenesis and neurovirulence of this newly discovered neurotropic virus a s well as other neurotropic herpesviruses.