COMPARISON OF THE HEMAGGLUTINATION INHIBITION TEST AND THE SERUM NEUTRALIZATION TEST IN TRACHEAL ORGAN-CULTURES FOR TYPING INFECTIOUS-BRONCHITIS VIRUS-STRAINS

Five strains of infectious bronchitis (IB) virus, which had been compared antigenically by the serum neutralisation (SN) test in tracheal organ cultures (OC), were arbitarily coded and then compared by the haemagglutination inhibition (HI) test. Their antigenic relationships were found to be similar by the two methods but, because of the high and variable cross reactions found in the HI test, the differences between the strains were less clear by that method. It was concluded that the HI test, in its present state of development, is considerably less type-specific than the SN test in OC, and cannot be recommended for defining antigentic relationships between strains of IB virus. However, it retains its value for diagnosing IB or for monitoring the vaccinal status of flocks.