Case Presentation:

A 61‐year‐old visiting Trinidadian woman with squamous‐cell rectal cancer and hypertension who had received multiple courses of chemotherapy and radiation therapy beginning in May 2012 and was hospitalized in July 2012 at a New York hospital for suspected chemotherapy‐induced anemia. During this hospitalization she received 3 units of packed red blood cells (pRBCs). Four weeks after discharge the patient completed her cisplatnin/etoposide and radiation regimens, with computed tomography imaging indicating successful remission of the carcinoma. Two weeks after completing the treatment the patient was transfused 2 units of pRBCs as an outpatient for persistent anemia. The patient was then readmitted 6 weeks later on October 10 at the same New York facility with suspected gastrointestinal bleeding. The patient presented with acute worsening of generalized weakness with associated nausea, vomiting, and dark stools. Further history revealed no changes in the patient's diet, absence of sick contacts, or travel outside Queens, New York, since her arrival in April. The patient's hematology labs on admission were notable for anemia, leukopenia, thrombocytopenia, and abnormal red blood cell morphology. Her stool was positive for fecal occult blood. These values were consistent with the patient's hematology values at the time of the last transfusion on August 24. Upper endoscopy colonoscopy and urinalysis were noncontributory; however, further anemia evaluation revealed evidence of intravascular hemolysis. Peripheral blood smear was performed and then evaluated by parasitology, confirming “ring forms” consistent with Babesia parasitemia in 1.1% of red blood cells.


Babesiosis is a tick‐borne parasitic infection that is an emerging health risk in several parts of the world. It is now classified as a nationally notifiable disease. Babesia microti is the most common organism implicated in babesiosis cases in the United States. The disease is often thought to present with constitutional symptoms; however, it commonly presents asymptomatically. In endemic areas, such as the south fork of Long Island, as much as 16% of the population demonstrates seroprevalence of the disease. Babesiosis in asplenic, neonatal, or otherwise immunocompromised patients can be fatal. Over the past decade there have been increasing case reports of clinically confirmed babesiosis in the absence of tick exposure.


(1) Babesiosis is often asymptomatic, and it should be considered in recipients of blood products with hemolytic anemia. (2) Babesiosis immunocompromised patient's presentation may be subclinical. (3) On diagnosis and in the absence of tick exposure, donor blood centers should be promptly contacted in order to initiate an investigation. (4) Transfusion‐transmitted infection is a risk to the national blood supply. (5) Cost‐effective blood donor babesiosis screening in endemic areas may limit Babesiosis emergence and improve health outcomes.