[Asymptomatic course of infectious bursitis in chickens]

Morphologic and serologic studies were carried out with a total of 190 birds of three breeds (Cornish, White Plymouth Rock, and Gillink) aged 1 to 50 days, with which Gumboro disease ran a symptomless course. Gross lesions were established in 3.1 per cent of the birds only. Histopathologically, however, there were changes in the bursa Fabricii (73.6 per cent), the spleen (68.4 per cent), the thymus (10.5 per cent), and the cecal tonsils (5.2 per cent). The microscopic lesions consisted in malacia of the elements of the lympho-reticular system. Serologically, mother precipitating antibodies were found in the first 2-3 weeks following hatching. The postinfection antibodies were shown to be released in the sixth to seventh week of even later. It was demonstrated that the symptomless course of infectious bursitis in birds could be histologically and serologically diagnosed as early as the first week following hatching, whereas the morphologic changes were mostly manifested between the 36th and the 50th day of age.