Comparison of live Newcastle disease vaccines in a simple vaccination and challenge experiment

Abstract

Groups of day-old chicks with haemagglutination inhibiting antibodies (HIA) were exposed by the spray method to equal doses of three different live Newcastle disease (ND) commercial vaccines and allantoic preparations of them. After three weeks the HIA response was measured and the chicks were challenged with a pathogenic strain of Newcastle disease virus (NDV). The degree of protection of each bird was compared with its HIA response. The commercial vaccines all provided good protection at identical levels, but significant differences were detected between the allantoic fluid preparations. Two of the commercial vaccines produced significantly better protection than the allantoic fluid preparations. In addition to the protection conferred by HIA antibody, other mechanisms of protection apparently played a part.