Newly isolated serotypes of infectious bronchitis virus: their role in disease.

The pathogenicity of isolates of infectious bronchitis virus (IBV) made from broiler or breeder flocks in Britain between 1981 and 1983, together with three made from flocks of commercial laying hens during 1984, has been investigated. When 11-day-old IBV-free chicks were challenged with these IBV isolates, together with a pool of pathogenic strains of E. coli, some mortality was recorded, together with a high incidence of morbidity. Three IBV isolates, when given to groups of IBV-free brown-egg laying hens, caused only a minimal effect on egg production but markedly affected egg shell colour.