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Comparative Study
. 2025 Dec 24;81(5):987-994.
doi: 10.1093/cid/ciaf034.

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

Loukas Kakoullis  1   2 , Carolyn D Alonso  2   3 , Rebecca Burns  2   3 , Muneerah M Aleissa  4 , Esther Arbona Haddad  2   5 , Andy J Kim  5 , Rebecca Rooks  5 , Bridget Yates  5 , Urwah Kanwal  5 , Nicholas P Morreale  5 , Alexandra Morgan  6 , Ramy Arnaout  6 , Alexandra Tong  5 , Natalie E Izaguirre  5 , Jessica S Little  2   5 , Sarah P Hammond  2   5   7 , Mary W Montgomery  2   5 , Amy C Sherman  2   5 , James H Maguire  2   5 , Ann E Woolley  2   5 , Lindsey R Baden  2   5 , Nicolas C Issa  2   5 , Courtney E Harris  8
Affiliations
Comparative Study

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

Loukas Kakoullis et al. Clin Infect Dis. .

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: 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).

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 < .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.

Conclusions: 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.

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

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