Babesiosis in a six-day-old calf.

Babesiosis was diagnosed in a six-day-old calf born indoors to a heifer which had been on a tick-infested pasture until 14 days before calving. The calf had typical symptoms of haemolytic anaemia and died after three days despite a blood transfusion. The erythrocytes in a blood smear made on the day it became ill were heavily infected with Babesia divergens and the lesions observed post mortem were similar to those described in babesiosis in adult cattle.