A direct plaque assay for hog cholera virus.

Direct plaque formation with representative strains of hog cholera virus (HCV) has been obtained using several pig kidney cell lines under agar overlay. HCV-infected cells appear as hazy plaques when viewed against an indirect light source, and as white plaques after neutral red staining. HCV assay by direct plaque procedure is rapid and convenient and gives infectivity titres identical to the fluorescent focus assay technique.