Detection of pseudorabies virus DNA in individual single-reactor pigs found in certified pseudorabies-free herds

During monitoring of certified pseudorabies (PRV)-free herds to confirm the ir PRV-free status, occasional individual gE-seropositive pigs are detected . These single-reactor pigs remain gE-seropositive when further serum sampl es are collected and tested. For the eradication programme to proceed, it i s important to determine whether these pigs are only false positives or are ; in fact, infected with field PRV. The purpose of this study was to determ ine whether the polymerase chain reaction (PCR) could detect field PRV DNA in single-reactor pigs and so confirm positive reactions in the serologic m onitoring programme. First, DNA samples of various tissues from 15 single-r eactor pigs all from different herds were examined for field PRV by PCR. Ad ditionally, serum samples from these pigs were analyzed in a gE-confirmatio n enzyme linked immunosorbent assay (gE-confirmation ELISA). PCR detected P RV DNA in five of the 15 pigs, and these results were confirmed by the gE-c onfirmation ELISA. The remaining 10 pigs that tested negative in the PCR al so tested negative in the gE-confirmation ELISA. We conclude that PCR can b e used to discriminate between true and false serological positive single-r eactor pigs and, moreover, that the gE-confirmation ELISA confirms these PC R results. (C) 1999 Harcourt Publishers Limited.