[Yucaipa-like viruses isolated in Kazakhstan in 1987-1989].

From domestic birds 13 strains of avian paramyxoviruses, serotype 1, and 14 strains of serotype 2 were isolated. Avian paramyxoviruses, serotype 2, differ antigenically and biologically from each other and from the prototype variant chicken/Yucaipa/California/56. The virus was also detected experimentally in birds having contact with the infected specimens. Examinations of avian blood sera revealed wide dissemination of viruses related to the chicken/Yucaipa/56 strain in domestic bird breeding farms (43.6% to 50.0% of positive birds). The detected variability of the antigenic structure of the isolates attests to the potential emergence of a pathogenic variant.