Polymerase chain reaction amplification of latent Aujeszky's disease virus in dexamethasone treated pigs.

A polymerase chain reaction (PCR) amplification assay was developed for the detection of Aujeszky's disease virus (ADV) DNA in cell cultures and clinical samples. Pigs vaccinated with commercial ADV vaccines and challenged with a field isolate of ADV were immunosuppressed by dexamethasone treatment. Nasal swabs collected from the pigs at various times post-immunosuppression showed that ADV was excreted for at least four to six days starting from day 8 or day 10 following dexamethasone treatment, by virus isolation and/or PCR. However, PCR only detected latent ADV in the trigeminal ganglia, mandibular lymph node, spleen and tonsils, but not in the brain stem, pons and olfactory lobe of two pigs following dexamethasone treatment, whereas tissue explanation and cocultivation failed to demonstrate the presence of the virus.