Afebrile but Infected: Severe Babesiosis Requiring Exchange Transfusion in an Elderly Patient

Introduction: Babesiosis is a tickborne illness endemic to the Northeastern United States with testing often performed on locals with fever, anemia, thrombocytopenia, and transaminitis. Babesia may be overlooked without known exposure or typical clinical features. Prognosis ranges from asymptomatic to death with increased risk of severe disease with age >50. There is limited data supporting red blood cell (RBC) exchange transfusion in babesiosis and the effect on time to parasite clearance is not well defined.


Description: An 84-year-old immunocompetent female presented to a Massachusetts emergency department with several days of subjective fevers, malaise, anorexia, dyspnea, and encephalopathy. She had relocated from Florida 6 weeks prior. She was afebrile and mildly hypoxic with acute severe anemia, thrombocytopenia, transaminitis, and hyperbilirubinemia, and was admitted for heart failure exacerbation. Within 2 days of hospitalization, anemia worsened requiring multiple RBC transfusions, and workup was consistent with hemolytic anemia. Given peripheral smear with rare schistocytes, new acute kidney injury, and encephalopathy, thrombotic thrombocytopenic purpura (TTP) was suspected. Over the next 24 hours, she was transferred to the ICU for undifferentiated shock requiring pressors and completed plasma exchange (TPE) for presumed TTP pending further testing. Within 12 hours of TPE, peripheral smear revealed 10-15% intraerythrocytic parasites consistent with babesiosis (later confirmed with babesia PCR). Despite severe illness, she remained afebrile. Treatment with atovaquone, azithromycin, and RBC exchange was immediately initiated with post-procedure parasitemia of 2.9%. On further investigation, the patient had been exposed to dogs that frequented wooded areas on Long Island prior to hospitalization. Time to parasite clearance was 3 days with significant clinical improvement before discharge.


Discussion: Babesiosis can cause life-threatening illness that mimics TTP in the absence of acute fever in geriatric patients. Workup for babesiosis should not be delayed in afebrile patients with hemolytic anemia, thrombocytopenia, transaminitis, and any travel to endemic areas despite lack of confirmed tick exposure. In cases with high-grade parasitemia and shock, exchange transfusion should be considered.