Study Illuminates Benefits of Red Blood Cell Exchange in Severe Babesiosis

A new study led by investigators from Mass General Brigham and Yale School of Public Health reveals that red blood cell exchange transfusion (ET) may provide critical benefits for patients hospitalized with severe babesiosis. Babesiosis is a tick-borne parasitic disease that infects red blood cells and can have life-threatening complications. ET, a procedure sometimes used in severe cases, involves removing a patient’s infected red blood cells and replacing them with healthy donor red blood cells. The study’s results, published in JAMA Internal Medicine, have the potential to improve outcomes for patients with severe disease.

"Reported cases of babesiosis in the United States have increased over the past several decades, yet large-scale, high-quality data to guide the treatment of severe babesiosis—including the role of exchange transfusion—remain limited,” said lead author David E. Leaf, MD, MMSc, an associate physician in the Renal Division of the Mass General Brigham Department of Medicine and an associate professor of Medicine at Harvard Medical School. “Our study provides the first large, multicenter evidence demonstrating that ET is associated with a substantially lower risk of in-hospital death or readmission.”

Babesiosis is a tick-borne illness found primarily in the northeastern and upper Midwestern U.S., as well as parts of Europe and Asia. It is transmitted by the same tick that carries Lyme disease. Babesiosis can lead to severe illness, including multi-organ failure and even death, especially in high-risk patients such as the elderly or immunocompromised. The current standard treatment for babesiosis involves antibiotics, but this treatment may be insufficient in more severe cases. The use of ET remains a topic of debate among providers, as it is an invasive and resource-intensive treatment, and data on its effectiveness remains limited. This study provides the first comprehensive data assessing whether ET improves clinical outcomes for patients with severe babesiosis, a disease historically under-researched.

The study used data from over 3,000 patients hospitalized with babesiosis at 82 medical centers across the northeastern U.S. over a 15-year period. Of the 629 severely ill patients included in the analysis, 33% received ET within the first seven days of hospitalization. The results showed that the composite endpoint of in-hospital death or 30-day readmission occurred in 3.6% of patients treated with ET, compared to 9.8% of those who did not receive ET.

“Our study shows that among patients hospitalized with severe babesiosis, those who received exchange transfusion were significantly less likely to die in the hospital or be readmitted within 30 days compared to those who did not receive ET,” said senior author Peter J. Krause, MD, a senior research scientist at Yale School of Public Health and Yale School of Medicine. “Even though the patients who received exchange transfusion were initially more severely ill, their outcomes were significantly better. This study provides strong evidence that exchange transfusion improves outcomes in high-risk patients.”

The study noted limitations, including residual imbalances in certain baseline patient characteristics. Future research is necessary to further identify which patients are most likely to benefit from ET, especially among those with less severe illness.

"This project represents a grassroots, investigator-initiated effort that brought together more than 100 collaborators across numerous hospitals and specialties, underscoring the power of large-scale, community-driven research to address important clinical questions,” said Leaf. “As cases continue to rise, improving recognition of severe babesiosis and ensuring access to effective treatments such as exchange transfusion will be critical.”

Authorship: In addition to David Leaf, Mass General Brigham authors include Audrey E. Monson, Julie-Alexia Dias, Rebecca Wenzel-Rideout, Julio Javier Baigorri, Aranya Bagchi, Ahmad Jaser, Guillermo Socorro Matos, Daniel Sanchez-Almanzar, Steven T. Hoge, Tushar Shenoy, Shoba Krishnamurthy, Sarah A. Kaufner, Jack A. Blau, and Ann Woolley. A large research team from the Yale School of Medicine, in addition to Peter Krause, also contributed to the study.

Disclosures: David E. Leaf received research support, unrelated to the current project, from BTG International, Metro International Biotech LLC, Renibus Therapeutics, Inc., Alexion Pharmaceuticals, and 60 Degrees Pharmaceuticals, Inc, and served as a consultant for MexBrain, Entrada Therapeutics, CardioRenal Systems, Inc., and Alexion Pharmaceuticals. Peter J. Krause received payments, unrelated to this project, from UpToDate, Inc, 60 Degrees Pharmaceuticals, Inc, and Pfizer, Inc, and serves on the American Lyme Disease Foundation Board of Directors.

Funding: Llura A. Gund Fund for Vector-Borne Disease Research and the Gordon and Llura Gund Foundation (PJK).

Paper cited: Leaf, D., et al. “Red Blood Cell Exchange Therapy for Severe Babesiosis” JAMA Internal Medicine DOI: 10.1001/jamainternmed.2026.0244