To clarify the incidence of avian infectious bronchitis (IB) in the field and serological types of IB virus, surveys of virus neutralizing (VN) antibodies were performed on chickens in Tottori prefecture. The results are as follows.
1. For the VN test, four strains of IB virus, Beaudette-42, KH (isolated in Japan), Holte and A-5968 were used as antigens. Consequently, in six of eleven flocks examined, the antibodies against one to four IB viruses used were demonstrated.
2. Four stocks showing some clinical signs, from two of which IB viruses were isolated, were immune to viruses used.
3. Out of the six immune flocks, five showed high VN titer to the Massachusettstype viruses. Thus this type of virus may have been distributed predominantly in this area. Moreover it was considered that the Connecticut-type virus affected the remaining one flock.
4. When investigations on the distribution of neutralizing antibodies against IB virus are performed, IB viruses of different serological types should be used as antigens.