Pathological changes in HPCD pigs with prednisolone induced recrudescence of pseudorabies virus.

In HPCD pigs inoculated with PRV, latent PRV could be reactivated in-vivo by the administration of large doses of prednisolone 3 months after the primary infection. In two pigs, virus shedding was without clinical signs of disease, whereas depression of circulating lymphocytes was prominent. Reactivation of PRV was also demonstrated by cultivation of the brain cortex on the 7th day and the mandibular lymph node on the 9th day after the prednisolone began treatment. Coincident with the virus isolation, characteristic lesions were observed in 2 pigs in the central nervous tissues and mandibular lymph nodes and these were composed of cell necrosis and eosinophilic intranuclear inclusion bodies. Cells containing the intranuclear inclusion bodies had immature and mature PRV particles. Results of the present study with HPCD pigs indicated that the lesions in the brain and lymph node accompanied by eosinophilic intranuclear inclusion bodies were pathogonomonic lesions induced by reactivation of PRV.