HISTOLOGY, IMMUNOHISTOCHEMISTRY, AND ULTRASTRUCTURE OF HYDROPERICARDIUM SYNDROME IN ADULT BROILER BREEDERS AND BROILER CHICKS - CASE-REPORT

Ten 250-day-old broiler breeders, seven 16-day-old broiler chicks, and three 25-day-old broiler chicks suffering from hydropericardium syndr ome (HPS) in Japan were examined histologically, immunohistochemically , and ultrastructurally. Clinically, the chickens died suddenly withou t apparent signs. The mortality rates were 6.4%, 20.2%, and 26.1%, res pectively. The common characteristic histologic lesion was necrosis of hepatocytes, accompanied by intranuclear inclusions of hepatocytes an d hemorrhages. In the spleen, there were activation of macrophages in splenic sinus and ellipsoids and erythrophagocytosis in the splenic si nus. The interlobular interstitium of the lung showed marked edema. Th e air and blood capillary areas of parabronchi included many macrophag es with yellow pigments. With immunoperoxidase staining, intranuclear inclusion bodies within degenerating hepatocytes stained positively fo r group I adenovirus antigen. Ultrastructurally, numerous viral partic les (65-70 nm in diameter) were demonstrated in the intranuclear inclu sions of hepatocytes. Group I adenovirus (serotype 4) was isolated fro m liver samples of adult broiler breeders and broiler chicks with HPS. This study suggests that HPS may be caused by group I adenovirus.