Tick-borne alpha-gal syndrome poses potential risks during blood transfusions

A new multi-institute study led by researchers at Dartmouth Health and Geisel School of Medicine at Dartmouth suggests that alpha-gal syndrome, the tick-borne disease that can result in a chronic allergy to meat and animal byproducts, also may complicate certain patients' ability to safely receive a blood plasma or platelet transfusion.

Alpha-gal syndrome (AGS) is a serious allergy transmitted by a sugar molecule called alpha-gal in the saliva of Lone Star ticks. First documented in 2025, the allergy is triggered by ingesting meat from mammals, such as beef, pork and lamb, as well as other products from these animals, like dairy and gelatin. An AGS reaction can trigger delayed, severe reactions like hives, stomach pain and anaphylaxis.

At the same time, Dartmouth Health's Dartmouth Hitchcock Medical Center (DHMC) has seen an uptick in recent years of patients with type O blood experiencing severe and even life-threatening allergic reactions after receiving platelets or plasma from type B or AB donors.

DHMC pathologists Nancy M. Dunbar, MD, and Richard M. Kaufman, MD, who led the study published August 24 in JAMA Internal Medicine, hypothesized that these patients may have pre-existing antibodies to alpha-gal from tick bites, and that hospitals in regions with higher concentrations of AGS patients, like DHMC, might also see an increase of allergic reactions in O patients receiving B or AB units. The international team of researchers now reports that transfusion-related alpha-gal syndrome, or TRAGS, is a legitimate manifestation of AGS and should be taken into account in the safety practices of hospital transfusion services.

We anticipate that this will change transfusion practices in the U.S., at least in AGS high-prevalence regions. DHMC has already taken the step to cease giving transfusions of B or AB platelets to O patients to avoid potential injury to these patients."

Richard M. Kaufman, MD, study's corresponding author and professor of pathology and laboratory medicine, Geisel School of Medicine

Dunbar and Kaufman's study was carried out at 40 sites in five countries, where over 550,000 platelet and plasma transfusions were analyzed. The study also included Anne G. Hoen, PhD, an associate professor of epidemiology, biomedical data science, and microbiology and immunology at Geisel.

In the study's nine U.S. sites in areas with high concentrations of AGS, significantly more allergic transfusion reactions were reported among type O patients who received B or AB units compared to type O patients who received O units.

"The changing climate and ensuing greater proliferation of ticks is leading to illnesses and symptoms we had not seen before, and we continue to learn about them in real time," said Dunbar, the study's senior author and a professor of medicine and pathology and laboratory medicine at Geisel. "AGS is a particularly fascinating and challenging tickborne disease as it causes this life-threatening allergy the patient did not have before, and now we know the risk is even greater for AGS patients who are type O. It is our hope that other hospitals, especially in regions with high tick populations, will follow DHMC's lead and avoid B and AB units for O-group patients in need of platelet or plasma transfusion. Even if it's an abundance of caution, it could save the patient's life."