For this research project 120 one-day old broiler chicks were divided into two groups i.e., A and B. The birds in group B were challenged with the H.P.S. agent at 15 days of age, whereas those in group A were dealt with as control birds. After the appearance of the syndrome serum samples were obtained from the diseased as well as control birds and then they were all perfused with 1% silver nitrate solution. Tissue samples from heart, liver, lungs, kidneys, spleen and bursa of fabricius were collected, processed and slides were prepared and stained by Haematoxylin and Eosin staining technique. In addition, tissue sections from all the organs were also stained by Silver nitrate impregnation technique.

The most peculiar post-mortem finding was over distension of the pericardial sac with clear or amber coloured fluid. The heart was mis-shaped, flabby with petechial haemorrhages on the epicardium. The liver was congested, swollen, friable with multiple pale areas of necrosis. Kidneys were enlarged, congested and dark in colour. The renal tissue was found to be much friable. Lungs were oedematous, congested and dark. The spleen showed congestion and haemorrhages. Bursa of fabricius was found to have normal appearance in some cases while in others showed slight atrophy.

For this research project 120 one-day old broiler chicks were divided into two groups i.e., A and B. The birds in group B were challenged with the H.P.S. agent at 15 days of age, whereas those in group A were dealt with as control birds. After the appearance of the syndrome serum samples were obtained from the diseased as well as control birds and then they were all perfused with 1% silver nitrate solution. Tissue samples from heart, liver, lungs, kidneys, spleen and bursa of fabricius were collected, processed and slides were prepared and stained by Haematoxylin and Eosin staining technique. In addition, tissue sections from all the organs were also stained by Silver nitrate impregnation technique.

The most peculiar post-mortem finding was over distension of the pericardial sac with clear or amber coloured fluid. The heart was mis-shaped, flabby with petechial haemorrhages on the epicardium. The liver was congested, swollen, friable with multiple pale areas of necrosis. Kidneys were enlarged, congested and dark in colour. The renal tissue was found to be much friable. Lungs were oedematous, congested and dark. The spleen showed congestion and haemorrhages. Bursa of fabricius was found to have normal appearance in some cases while in others showed slight atrophy.

The histopathological study of tissue sections stained by H&E staining technique revealed necrosis, accumulation of mononuclear cells and haemorrhages in the heart. The characteristic feature of liver was coagulative necrosis with disruption of hepatic cords. Some hepatocytes had basophilic intranuclear inclusion bodies. Renal tissue showed massive necrosis and degeneration of tubular epithelium along with lymphocytic infiltration. The lungs had oederna and mononuclear cell infiltration. The spleen showed degeneration, necrosis and haernorrhages while bursa of fabricius exhibited disruptions in the epithelial covering of its follicles.

Silver nitrate impregnation explored distinct changes in the blood vessels. There was disruption of the capillary endothelium along with accumulation of oedema fluid around the capillaries and an increase in the size of intercellular spaces.

The data, obtained by the analysis of serum, statistically indicated that the concentration of serum sodium, potassium, urea and uric acid increased greatly whereas the total serum proteins were markedly decreased in the affected birds. Thus it can be concluded from this study that disruption of the capillary endothelium and severe damage and malfunctioning of the heart, liver and kidneys appear to play a predominant role in the development of edema in this syndrome.