Causes of losses including a Borna disease paralytic syndrome affecting young ostriches of one breeding organization over a five-year period (1989-1993).

Necropsy records and causes of mortality of ostriches up to 3 months old over a 5-year period (1989-1993) are presented. The data relate to one ostrich enterprise that comprises 10 breeding flocks, five rearing farms, and one hatchery. Causes of mortality are classified into nine major categories. The annual mortality percentages of all hatched ostriches over the 5-year period were 61%, 58%, 30%, 29%, and 16.6%, and the most significant cause of death was a paresis syndrome that accounted for 20%, 11%, 16%, 10.1%, and 2% mortality, respectively. Limb deformities and gastroenteritis were the other principal specific causes of mortality. The paresis syndrome was caused by an agent serologically related to Borna disease virus. Brain extracts from paralyzed ostriches, when given orally or intramuscularly to 5-week-old birds, reproduced the clinical signs and microscopic lesions. The mean time to death was less than 3 weeks for the intramuscularly infected group and was almost twice as long for the orally infected group.