Vaccination against Newcastle disease and infectious bronchitis. 2. Field trials in mass vaccination with live virus dust vaccines. Poultry Sci

DATA have been presented elsewhere (Markham et al., 1955) indicating that, under laboratory and limited field conditions, micronized vaccines prepared from the B-1 strain of Newcastle disease virus and the DG strain of infectious bronchitis virus, individually or in com-bination, can be successfully employed for mass vaccination when dispersed as dusts over the heads of birds. The efficacy of the method was determined by means of hemagglutination-inhibition and serum neutralization test, and by challenge with virulent virus. To amplify those prelimi-nary observations, a series of carefully supervised field trials was instituted i