Characterisation of strains of infectious bronchitis virus isolated in Chile

Nine isolates of infectious bronchitis (IB)-like viruses were made from 23 flocks (broilers or layers) in Chile experiencing the types of disease problems commonly associated with IBV. Their identity as IB viruses was confirmed. The histological changes they caused in tracheal organ cultures (OC) are described. Serum neutralisation tests performed in embryonated eggs (alpha-method) suggested that four of the isolates were serologically related to the Massachusetts (Mass) serotype of IBV and one to Connecticut. The four other strains were examined further by a serum neutralisation test in OC (ss-method). One was found to be of the Mass serotype but the others were found to be unrelated antigenically to a wide range of IBV serotypes isolated in many countries over a number of years. One of these three strains and the Mass strain, when given intranasally to 8-day-old specified pathogen free chickens together with pathogenic serotypes of E.coli, caused some mortality and considerable morbidity. The H120 vaccine strain was found not to protect completely against challenge with these four strains 21 days later.