Some Studies on the Infectious Bursal Agent

A condition causing considerable mortality in young chickens, described by Cosgrove in 1962 (1), has been designated Gumboro disease. The same year Winterfield et al. (4) isolated and identified the causative virus and suggested the name bursal (IBA) for it. Helmboldt and Garner described the pathology of the disease in 1964 (2). When first recognized, infectious bursal disease (IBD) produced high mortality in affected flocks and spread rapidly throughout the Delmarva Peninsula and other broiler-producing areas. The disease tends to recur in successive flocks, and the mortality in each outbreak usually decreases. On some farms, however, severe losses occur in flock after flock in spite of good sanitary measures. Since an attack of the disease seemed to produce immunity, an attempt was made to egg-propagate and attenuate the causative agent sufficiently to produce an effective vaccine.