[Serological diagnosis of IBR. Comparative studies of cattle sera in the virus neurtalization and passive hemagglutination reactions].

Three hundred eighty six cattle serums were simultaneously investigated by virus neutralizing (VN) and passive hemagglutination (PSH) reactions. Results obtained by the two methods coincided in 94% of the sermums studied and all serums with VN antibodies had also antibodies which can be established by the PSH reaction. About 6% of the positive reagents for PSH reaction were negative for the VN reaction. These were serums containing early antibodies (IgM) or low-titer antibodies of the IgG class, and were subtreshold for the VN reaction. The antibody titers determined by the PSH reaction were 7 to 10 times higher than these determined by the VN reaction, while their mean titer in serums with minimum VN index 1.0 was 1:23. The conclusion is drawn that PSH can be used as an independent serological test.