The Brief case: Probable transfusion-transmitted babesiosis in a transplant recipient

Kitt E, Keaton AA, Graf EH.
Journal of Clinical Microbiology 54:2632–2634.


A 3-year-old immunocompromised male who had been hospitalized for 7 months in the cardiac intensive care unit developed fever and tachycardia in December. He was prenatally diagnosed with hypoplastic left heart syndrome and received right ventricle to pulmonary artery conduit surgery days after delivery. Due to worsening right ventricular function, after a hemi-Fontan procedure, he received an orthotopic heart transplant at the beginning of his 3rd year of life.

His posttransplant course was complicated by multiple episodes of rejection, cytomegalovirus (CMV) pneumonitis, and several central-line-associated bloodstream infections. As a result of the rejection, necessitating plasmapheresis as well as frequent blood draws for management, which led to anemia, he received 36 packed red blood cell transfusions over the course of 7 months posttransplantation. These transfusions were evenly spaced, and he remained hospitalized during the 7 months.

At the time of the febrile episode, he was on caspofungin, trimethoprim-sulfamethoxazole, and ganciclovir. The subsequent diagnostic workup included multiple sets of blood cultures, a urine culture, and a CMV viral load analysis. He was started on vancomycin and cefepime while awaiting microbiologic results. Other pertinent test results included a complete blood count (CBC) with differential showing pancytopenia and an aspartate transaminase (AST) level of 200 U/liter (reference range, 20 to 60 U/liter), an alanine aminotransferase (ALT) level of 84 U/liter (reference range, 5 to 45 U/liter), and a C-reactive protein level of 3.1 mg/dl (reference range, 0 to 0.9 mg/dl), which increased to 7.1 mg/dl over 4 days.

On the 5th day of fever, another CBC with differential was ordered and was noted by the hematopathologist to contain intraerythrocytic parasites. Immediately, a blood smear with Giemsa stain (Harleco Giemsa stain; EMD Millipore, Billerica, MA, USA) was performed by the microbiology laboratory, yielding the definitive diagnosis. Babesia species with a parasitemia level of 18% was reported to the clinical team. Real-time PCR testing, performed by a reference laboratory, provided the species-level identity of Babesia microti. All other infectious workups were negative. The patient was started on azithromycin plus atovaquone due to the contraindications against treatment with quinidine (QT interval prolongation in a heart transplant recipient with declining heart function).

Three days later, clindamycin was added when his parasitemia level did not decline. He was also given an exchange transfusion on day 4 after diagnosis in an attempt to reduce his parasitemia. After 14 days of therapy, his parasitemia became undetectable and he completed 6 full weeks of therapy, at which time he remained aparasitemic. Since transfusion was the child’s only known risk factor for Babesia infection, a complete investigation into the blood products used was conducted, but the infectious unit/donor could not be definitively identified. Banked products from the organ donor were also tested, and it was determined that the heart transplant was not the source of the Babesia infection.