DNA restriction fragment length polymorphism among British isolates of Aujeszky's disease virus: use of the polymerase chain reaction to discriminate among strains.

A retrospective analysis of DNA restriction fragment length polymorphism (RFLP) of Aujeszky's disease (AD) virus isolates from England and Wales over a 22-year period revealed considerable homogeneity of BamHI restriction endonuclease sites, both in number and size. The appearance of a new DNA RFLP in 1981 coincided with a marked increase in the number of new outbreaks of AD. A polymerase chain reaction (PCR) method was developed to discriminate between the established strains and the new type. By relating these results to pig movement records it was possible to trace the spread of the new type virus which was isolated from 39/60 (65%) of the new outbreaks of AD in England and Wales in 1982. The study suggested that airborne spread of up to 17 km was the most likely route of transmission in many of the new type cases. The discriminatory PCR was shown to be a useful tool for the rapid and sensitive detection of latent AD virus in pigs.