Isolation of pseudorabies virus from trigeminal ganglia of a latently infected sow

A 2-year-old sow with a relatively low virus-neutralization (VN) titer (1:8) against pseudorabies virus (PRV) was brought to the National Animal Disease Center for observation and study. The sow was kept in isolation for approximately 6 weeks, and repeated nasal and tonsillar swabs for virus isolation and blood samples for VN tests were obtained during this interval. At the end of 5 weeks' observation, the sow was injected IM with 200 mg of dexamethasone and was euthanatized 1 week later. Parts of the two trigeminal ganglia, tonsillar tissue, and nasal secretions were cultured in porcine kidney cells. The rest of the trigeminal ganglia was extracted with phenol and tested for presence of the PRV-DNA genome by hybridization with tritiated complementary RNA. The PRV was isolated from the trigeminal ganglia only, and the PRV genome was demonstrated in the same tissue. This latently infected sow was a potential shedder of PRV.