New strains of infectious bronchitis virus isolated in Maine.

Twelve IBV isolants from diseased chickens in Maine were studied by serum-neutralization tests in chicken tracheal culture. Six isolants were neutralized by Mass-type antisera. The serum-neutralizing characteristics of six other isolants from vaccine breaks differed from any of the standard IBV viruses and appear to comprise three new strains, Maine 209, 212,and 246. The data provide additional evidence that strains of IBV responsible for disease probably vary from region to region and that the strains present must be known for a regional vaccination program to be effective.