Hydrops foetalis in sheep.

Hydrops foetalis was observed in foetuses from a sheep flock in southern New South Wales over 4 years. Ewes showed marked abdominal distension and most died at parturition, being unable to deliver large affected foetuses. These had birth weights up to 18 kg and exhibited severe generalised oedema of subcutaneous tissues, fluid accumulation in the serous cavities and oedema of the placenta. Microscopically, there was a generalised extramedullary haemopoiesis and massive oedema, consistent with a chronic foetal anaemia. No infectious or environmental factors could be incriminated in the outbreak. The clinical and pathological findings resemble those of the homozygous alpha-thalassaemia in infants associated with haemoglobin Bart's.