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

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.

This 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).

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 < .0001) and higher rates of complications, including acute kidney injury (24% vs 11%, P = .016) and acute respiratory distress syndrome (11% vs 4%, P = .041), and were more likely to undergo packed red blood cell transfusion (31% vs 17%, P = .023) and exchange transfusion (18% vs 6%, P = .008). Treatment duration was longer in the ICAH cohort (median 27 vs 10 days, P < .001), particularly in those with both IC and AH (median 43 days, P = .003). ICAH patients had higher 12-month all-cause mortality (7% vs 1%, P = .019) and recurrence rates (8% vs 0%, P = .001). Hematologic malignancy (odds ratio = 7.0, P = .023) and B-cell-depleting therapies (odds ratio = 9.4, P = .015) were significant predictors of recurrence. Despite most patients undergoing follow-up testing with blood smears and polymerase chain reaction, these did not reliably predict recurrence.

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