Demonstration of specific antigen(s):
The presence of the viral antigen in the infected tissues and cells can be demonstrated by fluorescent antibody technique (FAT) and immunoperoxidase test (IPT) either in impression smears or in tissue sections cut in frozen state. Formalin fixed tissue can also be used for FAT and IPT. Other serological tests, viz. agar gel precipitation test (AGPT), counter immuno-electrophoresis (CIE), complement fixation test (CFT), rocket immuno-electrophoresis (RIE), enzyme-linked immunosorbent assay (ELISA), single radial haemolysis (SRH), agglutination and conglutinating complement adsorption test (CCAT) may also be utilized for the purpose depending upon their suitability in a particular infection.