Isolation of an antigenically unusual paramyxovirus type 1 from chickens

An antigenically unusual paramyxovirus type 1, designated PMV-1/ chicken/Ulster/Espey/86, was isolated from 22-week-old broiler breeders. Using cross-haemagglutination inhibition tests, this virus showed a predominantly one-way cross with the Ulster 2C strain of Newcastle disease virus (NDV). Antisera to NDV had similar titres to Ulster 2C NDV and to PMV-1/Espey, but convalescent antisera to PMV-1/ Espey had substantially lower titres to NDV than to the homologous virus. These low antibody titres could in some circumstances be ignored or misinterpreted as being non-specific, particularly as PMV-1/Espey was shown to be avirulent for chickens.