Brain lesions and transmission of experimental equine herpesvirus type 9 in pigs.

We demonstrated that pigs are susceptible to acute infection by equine herpesvirus type 9 (EHV-9). Six 8-week-old SPF pigs were inoculated intranasally and four were inoculated orally with different doses of EHV-9, and observed for 6 days. Although neurological signs did not develop in any of the infected pigs, the six intranasally infected pigs and one of the orally infected pigs developed lesions of encephalitis consisting of neuronal necrosis, neuronophagia, and intranuclear inclusion bodies, distributed mainly in the rhinencephalon. EHV-9 antigen was localized in the necrotic neuronal cells and was closely associated with the presence of inclusion bodies. These findings clearly demonstrate that pigs are fully susceptible to EHV-9 infection following intranasal inoculation (but less so following oral inoculation), and that EHV-9 in pigs has a highly neurotropic nature.