RESUMO
An owner of a pigeon farm in Buraydah [Central Saudi Arabia] complained that one of his birds developed abnormal behaviour and signs. Clinically the bird was unable to flight, running into objects and showed unusual movement of the head and neck together with weakness of the muscles of legs and neck. In certain instances, the pigeon failed to hold the head in position and it dropped downward and rested on the ground. The head might also be twisted to face upwards or laterally. Sometimes the legs were so weak and the bird assumed a sitting position and was reluctant to move when pushed. Simple tests for vision [avoiding an approaching fingure towards the eyes] and hearing [Jerking to clamping] showed that the bird vision and hearning were normal. At certain times, the bird reverted to normal and when it offered grains and water, it ate and drank normally. The bird was kept in the Experimental Animal House at the Department of Veterinary medicine for observation but its condition deteriorated 4 days later and was sacrificed and post-mortemed. On post-mortem examination, no gross lesions could be observed in internal organs or the brain. Histopathological examination showed no microscopical lesions in the liver, heart or kidneys, but a nearly typical lesion of spongiform encephalopathy was seen in the brain. Small to very large vacuoles were seen in the cytoplasm of medullary neurons. Degeneration of some neurons was also seen especially around blood vessls