Studies on a new enterovirus-like virus isolated from chickens

During investigations into an outbreak of respiratory distress in broilers chicks, a small round virus was isolated following inoculation into chicken embryos. The isolate, designated 612, was identified as an enterovirus-like virus on the basis of its size and morphology, resistance to chloroform and to treatment at pH 3.0, and intracytoplasmic replication in cell culture. The virus produced a partial cytopathic effect following inoculation into chick embryo kidney cell cultures and viral antigens could be detected by immunostaining. The preferred culture method for 612 virus was by inoculation onto the CAM of chick embryos. Cross-immunofluorescence indicated that the virus is not antigenically related to five previously identified chicken enterovirus/enterovirus-like virus serogroups. Following experimental inoculation of 1-day-old male broilers a number of which had maternal antibody to 612, growth retardation ranging from 9.6 to 20.4% was detected. Serological studies demonstrated antibody to 612 virus was widespread in commercial chicken flocks in N. Ireland.