Histological development of lesions in the bursa of Fabricius of chickens with inclusion body hepatitis.

Twenty chickens, 4 weeks old, from a flock with spontaneous inclusion body hepatitis were observed for five weeks following the outbreak of disease. Biopsies were made of the bursae of Fabricius on days 1, 3 or 7, and 14 after housing, and the chickens were killed on day 35. Histologically, severe lesions in bursal follicles developed within a few days. At the end of the observation period the bursal structures had completely recovered.