Transmission of Babesia microti by blood transfusion in Texas.

In the USA, seasonal tickborne transmission of Babesia microti occurs in the Northeast and upper Midwest. A resident of Texas became infected through a red blood cell transfusion from an asymptomatic local donor who had summered in Massachusetts. The patient's infection was diagnosed by blood smear examination in January, 7 weeks post-transfusion. He died 1 week later from variceal haemorrhage complicated by haemolysis. Premortem patient specimens and archived blood from the donor unit tested positive for B. microti antibodies and DNA. Babesiosis should be included in the differential diagnosis of post-transfusion haemolytic anaemia or thrombocytopenia, regardless of the geographical region or season.