Babesia microti in a Canadian blood donor and lookback in a red blood cell recipient.

Background and Objectives: We describe the third documented case of autochthonous human babesiosis in Canada and the second in a Canadian blood donor.
Materials and Methods: Multiple laboratory investigations were carried out on the donor and the immunocompromised recipient of an associated, potentially infectious red blood cell product.
Results: The donor had not travelled except for outdoor exposure in south-eastern Manitoba, followed by illness and hospital admission. The donor had a notable parasitaemia, positive for Babesia microti using whole blood nucleic acid testing (NAT). The recipient was negative for B. microti by both serology and NAT.
Conclusion: There was no evidence of transfusion-transmitted babesiosis.
(© 2021 International Society of Blood Transfusion.)