Comparative Outcomes of Babesiosis in Immunocompromised and Non-Immunocompromised Hosts: A Multicenter Cohort Study

Abstract

Background: Babesiosis poses significant risks of adverse outcomes in individuals with immunocompromising conditions (IC) and asplenia/hyposplenia (AH). This study compares clinical outcomes between these vulnerable groups and immunocompetent patients.

Methods: A multicenter retrospective cohort study included adult patients with laboratory-confirmed babesiosis from 2009 to 2023. Complications, management, and outcomes were compared between patients with IC/AH (ICAH) and without ICAH (immune intact cohort).

Results: Of 225 patients (mean age 66 years, 36% female), 112 were ICAH. ICAH patients had higher median peak parasitemia (2.8% vs. 0.9%, p<0.0001) and higher rates of complications, including acute kidney injury (24% vs. 11%, p=0.016), acute respiratory distress syndrome (11% vs. 4%, p=0.041), and were more likely to undergo packed red blood cell transfusion (31% vs. 17%, p=0.023) and exchange transfusion (18% vs. 6%, p=0.008). Treatment duration was longer in the ICAH cohort (median 27 vs. 10 days, p<0.001), particularly in those with both IC and AH (median 43 days, p=0.003). ICAH patients had higher 12-month all-cause mortality (7% vs. 1%, p=0.019) and recurrence rates (8% vs. 0%, p=0.001). Hematologic malignancy (OR=7.0, p=0.023) and B-cell-depleting therapies (OR=9.4, p=0.015) were significant predictors of recurrence. Despite most patients undergoing follow-up testing with blood smears and PCR, these did not reliably predict recurrence.

Conclusion: Patients with ICAH with babesiosis experience more severe disease and higher complication rates. Follow-up testing, including blood smear and PCR, did not reliably predict recurrence, highlighting the need for more effective monitoring strategies in these high-risk populations.

Keywords: Babesia microti; TNF inhibitors; relapse; rituximab; transplant infectious diseases.