Objectives: Infectious bursal disease (IBD, Gumboro) is an acute, highly contagious viral infection. Avian amyloidosis is a well-recognized pathological disorder which is a common cause of death in birds, especially chickens. It is a fatal progressive condition in which an abnormal protein (amyloid) builds up within the bird's tissues and organs, leading to organ failure, due to biochemical reactions of some viruses. Amyloidosis represents substantial economic losses, in addition to welfare concerns. This study documented the histopathological changes in spleen tissue from samples birds. Infectious bursal disease with Diagnosis of amyloidosis was made with necropsy of spleen tissue. Materials and Methods: A total of 16 chickens were collected from poultry farm within 4 weeks of old and had clinical signs of infectious bursal disease. Since clinical signs of amyloidosis are non‐specific, diagnosis requires histopathology following biopsy or necropsy to obtain a definite diagnosis. The organs such as the spleen, liver, thymus and bursa fabricius were removed and fixed in 10% buffered formalin after postmortem examination. All tissue samples were embedded in paraffin, sectioned at 5 µ and stained with hematoxylin-eosin for histopathological observations. Results: Clinically the disease was seen only in chickens older than 3 weeks. The spleen was the most frequently and usually the most seriously affected organ, followed by the liver and then the thymus. Histopathology was observed in lymphoid tissues of spleen that occurred through the deposition of amyloid fibrils. Evolution of infection depends on age, race, level of maternal antibodies in chickens and virulence viruses. Amyloid deposits were also observed at a high rate in the tissues of apparently healthy chickens. Conclusion: The histopathological diagnosis of these pathologies can be contributing factors to differential diagnosis. Vaccination should therefore be considered as a potential risk factor for the development of amyloidosis in poultry. Do not administer multiple vaccines in one setting to chickens. Amyloid deposition in chickens may tend to regress when causative factors, such as vaccinations and/or chronic inflammation, are absent.
