Quantitative evaluation of syncytium formation in cell culture by British isolates of Aujeszky's disease virus

Measurement of the extent of syncytium formation by UK isolates of Aujeszky's disease virus growing in pig kidney cell cultures was a useful means of differentiating between them. Results correlated well with results of a virulence test performed in mice. Use of both markers together demonstrated the variation in biotype among nine isolates studied. Two of eight British isolates were relatively avirulent for mice and formed only a few syncytia. Two separate clones of one isolate were also differentiated using these markers. It was concluded that the syncytium size marker is a useful adjunct to existing methods of characterizing Aujeszky's disease virus strains.