The hydropericardium syndrome in poultry--a current scenario.

Inclusion-body hepatitis hydropericardium syndrome (IBH-HPS) is an important, recently emerged, disease of poultry, particularly of 3- to 6-week-old broiler chicks, characterized by its sudden onset, with high mortality ranging from 20% to 70%, typical hydropericardium and enlarged mottled and friable livers, with intranuclear inclusion bodies in the hepatocytes. The causative agent is a non-enveloped icosahedral fowl adenovirus (FAV) serotype 4, belonging to the Adenovirus genus of the family Adenoviridae, which can be propagated or cultivated in chicken embryo liver and kidney primary cell cultures. The transmission of disease occurs vertically and laterally by the oral-faecal route. The liver of infected birds shows necrotic foci and basophilic intranuclear inclusion bodies in the hepatocytes. The disease can be diagnosed from its gross and histopathological changes in the liver and by various serological tests, such as agar gel immunodiffusion, counterimmunoelectrophoresis, indirect haemagglutination, the fluorescent antibody technique, enzyme-linked immunosorbent assay and the polymerase chain reaction. The disease has been brought under control by the use of formalin-inactivated vaccines, prepared from infected liver homogenate, and of inactivated cell culture vaccines. The vaccines are effective in the face of natural outbreaks or experimental challenge and significantly reduce the mortality.