Agar gel precipitin line patterns and pathogenicity of infectious bursal disease viruses.

Twenty-nine strains of infectious bursal disease virus could be classified into three groups by the agar gel precipitin line patterns using two representative base antigens of F539 and G691 strains. The precipitin line of the first group (16 strains including F539) did not fuse with that of G691 base antigen and spur was seen. The line of the second group (2 strains) did not fuse with those of both base antigens. The line of the third group (11 strains including G691) did not fuse with that of F539 base antigen. Every strain of the first group was highly pathogenic for chickens showing a mortality of 40% or more.