Abstract
A hereditary nervous disorder in Fayoumi chickens is described. Affected chickens developed seizure symptoms characterized by sudden crouching to the ground with neck rigidly flexed. The duration of the seizure varied from case to case, usually lasting for 15 to 30 s. The seizure was triggered by unexpected loud noise, sudden movement, bright light and other audiovisual stimuli. The main histopathological lesions consisted of degeneration of small arteries, with cellular infiltration in the cerebrum of all chickens examined and demyelination and/or loss of nerve fibres with oedema and Schwann cell proliferation in the cervical spinal nerves of most birds. Genetic analysis revealed that the condition was heritable and apparently controlled by an autosomal recessive gene.