Heavy parasitemia in babesiosis treated without adjunctive red cell exchange.

Babesiosis is a tick-borne infectious disease caused by the protozoa Babesia but transplacental, and transfusion transmission may occur. While most infections are asymptomatic, rarely, it can present with a severe, life-threatening illness. Treatment is primarily with antibiotics, but red cell exchange (RCE) has been used in more severe cases which are characterized by high-grade parasitemia, evidence of severe hemolysis and or multi-organ failure. A threshold parasite level of 10% has arbitrarily been applied as an indication for RCE; however, this threshold is not evidence-based. We report on three cases of severe babesiosis in which we considered the use of RCE on the basis of a parasite level greater than 10%, but the procedure was not performed. We deferred RCE on account of the good clinical state of the patient and the absence of end-organ failure. All patients were followed daily until discharge. Two of these patients had been splenectomized, and each received a single unit of red blood cells during the hospitalization. The third patient had a long history of refractory lymphoma and was pancytopenic requiring multiple transfusions during the years before the diagnosis of babesiosis. She had transfusion-transmitted babesiosis from a red blood cell transfused 46 days prior to diagnosis. All three patients responded well to antibiotics, and none expired. This small case series suggests that requests for RCE solely on the basis of an arbitrary level of parasitemia should be questioned and the clinical state and evidence of end-organ failure considered in the decision to perform RCE.