Keeping Blood Transfusions Safe from Blood Parasite

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In the U.S., blood donations are considered safe and contracting infections from blood transfusions is uncommon. Careful screening of potential donors through questionnaires and testing donated blood for various microbes protects the blood supply. A new report looked at the number of infections spread through blood transfusions and found that, although such infections are rare, the parasite Babesia is one of the most common causes of the infections that do occur.

According to the Centers for Disease Control and Prevention (CDC), Babesia infection, also called babesiosis, is most often spread by the bite of certain ticks—the same ticks that carry Lyme disease. The ticks are most common in the Northeast and Midwest U.S., and in the spring and summer. Less common ways to acquire babesiosis include transmission through a blood transfusion and from a mother to her baby during pregnancy and delivery.

Not everyone infected with the Babesia parasite develops symptoms, but some people can have non-specific, flu-like symptoms such as fever, chills, sweating, headache, body ache, loss of appetite, nausea and fatigue. The parasites infect red blood cells and can cause them to burst. In some people, this may lead to a serious condition called hemolytic anemia (from the destruction of red blood cells). Babesiosis can be life threatening, especially in people who:

  • Don’t have a spleen (the spleen helps clear infected red blood cells from the blood)
  • Have a weak immune system, for example because of HIV/AIDS or cancer
  • Have other serious health conditions, such as liver or kidney disease
  • Are older than age 50

A new report on infections linked to blood transfusions was published in January in Transfusion Medical Reviews. It is based on data from the National Healthcare Safety Network (NHSN), a program of the CDC. According to the report, 7.9 million units of blood components (e.g., red blood cells, platelets) were transfused between 2010 and 2016 (the latest year for which data is available). In that time, a total of 111 suspected infections from transfusions were reported, 54 of which were confirmed through testing. Of those, 30% were due to Babesia, the only parasite reported. Overall, there was roughly 1 infection per 147,000 blood components transfused.

Even though transfusion-transmitted infections are rare, these infections can be serious and deadly. Taking steps that lower the risk of such infections, including babesiosis, can reduce illness and death in blood transfusion recipients.

Currently, potential blood donors are asked about possible Babesia infection in a questionnaire they fill out before donating blood. Individuals who have had a confirmed or suspected infection are not allowed to donate again (deferred indefinitely unless the guidelines change in the future). However, the report points out that since many people don’t get symptoms from a tick bite, they might not know whether they were infected.

On March 6, 2018, the Food and Drug Administration (FDA) approved the first two tests for screening blood donors as well as organ and tissue donors for Babesia infection. In a press release at the time, Peter Marks, M.D., Ph.D., director of the FDA’s Center for Biologics Evaluation and Research, remarked that “While babesiosis is both preventable and treatable, until today, there was no way to screen for infections amongst blood donors.”

In follow up, the FDA released draft guidance on testing blood donations for babesiosis in July 2018. Among the recommendations:

  • Testing each donation using the newly approved tests in fourteen states and Washington D.C. where Babesia infection is most likely (i.e., Connecticut, Delaware, Maine, Maryland, Minnesota, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, Virginia, Wisconsin). Testing should be done year-round.
  • People who test positive are not allowed to donate blood for at least two years.
  • Allowing donors with a history of babesiosis to donate blood if testing demonstrates that they don’t currently have an infection.
  • In states that don’t test donors, potential donors need to be asked about both a history of babesiosis and/or a positive test (either from diagnostic testing or donor screening in a state that does testing). Those with a history of infection are not allowed to donate unless guidelines change.

Organizations and blood donation centers including AABB, the American Red Cross and America’s Blood Centers have sent comments on the draft guidance. Among their comments is a recommendation that people with a positive babesiosis test be barred from donating for a shorter period than the recommendation in the draft guidelines (one-year deferral compared to two years).

The date for publication of the final version of the guidance is not known at this time. Until then, the FDA understands some blood donation facilities will implement babesiosis testing and they are advised to notify the FDA about the changes in their procedures to prevent the spread of babesiosis.

View Sources

Sept 28, 2018. Letter RE “Recommendations for Reducing the Risk of Transfusion Transmitted Babesiosis” draft guidance, July 27. Available online at Accessed February 22, 2019.

May 17, 2018. Parasites-Babesiosis. Centers for Disease Control and Prevention. Available online at Accessed February 22, 2019.

July 2018. Food and Drug Administration. Recommendations for Reducing the Risk of Transfusion-Transmitted Babesiosis. Draft Guidance for Industry. Available online at Accessed February 22, 2019.

March 6, 2018. Food and Drug Administration. FDA approves first tests to screen for tickborne parasite in whole blood and plasma to protect the U.S. blood supply. Available online at Accessed February 22, 2019.

Haass K, Transfusion-Transmitted Infections Reported to the National Healthcare Safety Network Hemovigilance Module (January 25, 2019). Available online at Accessed February 25, 2019.

(January 30, 2019) Babesia and Bacterial Contamination Most Frequent Transfusion-Transmitted Infections. Transfusion News. Available online at Accessed February 25, 2019.