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Summary
The properties of four serotypes of New Zealand Infectious Bronchitis (IB) virus in the 10th and the 40th to 50th egg passage were investigated. All viruses were chloro-form-sensitive. Three types in the 10th egg passage were inactivated by heating to 56°C within 10 minutes, the fourth one within 30 minutes. The growth curve of all viruses at a low and a high passage level has been determined.
On the basis of degree of attenuation and type-distribution in the New Zealand poultry population an isolate of serotype A in the 46th egg passage was selected as being the most suitable seed virus for a New Zealand IB vaccine.