Transmission of Babesia microti Parasites by Solid Organ Transplantation

Abstract

Babesia microti, an intraerythrocytic parasite, is tickborne in nature. In contrast to transmission by blood transfusion, which has been well documented, transmission associated with solid organ transplantation has not been reported. We describe parasitologically confirmed cases of babesiosis diagnosed ≈8 weeks posttransplantation in 2 recipients of renal allografts from an organ donor who was multiply transfused on the day he died from traumatic injuries. The organ donor and recipients had no identified risk factors for tickborne infection. Antibodies against B. microti parasites were not detected by serologic testing of archived pretransplant specimens. However, 1 of the organ donor's blood donors was seropositive when tested postdonation and had risk factors for tick exposure. The organ donor probably served as a conduit of Babesia parasites from the seropositive blood donor to both kidney recipients. Babesiosis should be included in the differential diagnosis of unexplained fever and hemolytic anemia after blood transfusion or organ transplantation.

Keywords: Babesia microti; Minnesota; United States; Wisconsin; babesiosis; erythrocyte transfusion; hemolytic anemia; human babesiosis; kidney transplant; organ transplantation; parasites; protozoa; tissue donor; vector-borne infections.

Figure 1

Timelines showing key clinical and laboratory events for 2 renal transplant recipients (patients A and B) infected with Babesia microti parasites, Wisconsin, USA, 2008. Trauma, transfusions, death, and organ procurement for the organ donor all occurred on the same day in late August 2008. NPF, no parasites were found by examination of thick and thin blood smears.

Figure 2

Wright-stained peripheral blood smear from patient A (index case-patient), a renal transplant recipient infected with Babesia microti parasites, Wisconsin, USA, 2008. The smear shows intraerythrocytic Babesia parasites, a ring form (black arrow), and a Maltese cross or tetrad form (red arrow), which is pathognomonic for babesiosis. Scale bar indicates 10 μm.

Figure 3

Computed tomography (CT) scan of the abdomen of patient B, a renal transplant recipient infected with Babesia microti parasites, Wisconsin, USA, 2008. Taken on November 5, the scan shows a splenic infarction (white arrow) that had not been visualized on a CT scan on October 5. Although the cause of the splenic infarction was not determined, the infarction might have been a complication of babesiosis, as reported for other patients (16,17).