Plaque morphology of some South American strains of foot-and-mouth disease virus and the effects of polyionic compounds on plaque formation

Summary

The plaque forming ability of attenuated and field strains of FMDV of types A and O Vallée and C Waldmann were compared in BHK cell cultures. It was found that the vaccine strains attenuated by chick embryo passage produced smaller plaques. Reactor viruses recovered from vaccinated animals generally produced larger plaques than the vaccine and field strains. Type O vaccine, reactor and field viruses produced plaques of less variation in size and morphology. Field viruses of types A and C produced non-clear plaques which are readily distinguishable from the corresponding vaccine and reactor viruses.

All viruses produced larger plaques in the presence of dextran sulfate, whereas the plaque size was reduced with all viruses in the presence of DEAE-dextran. The plaque size and morphology of the field viruses were altered following passage in cell culture. The possible usefulness of these findings in relation to virus markers is discussed.

The results obtained in this study emphasize the necessity of comparing the characteristics of reactor virus with those of the vaccine and field strains.