Babesiosis: The Infectious Disease Spreading With Blood Transfusions

Experts call for better screening methods for donor blood after a study found the babesia parasite has infected at least 159 Americans


Ticks, whose bite has long been known to spread potentially devastating diseases like Lyme, have never been the most popular bug on the block. Now a new study reports that there's another tick-related disease to be aware of: The parasite Babesia microti can be transmitted through ticks, but it can also pass from one person to the next through blood transfusions at hospitals. Experts call for better screening methods for donor blood.

According to the background information in an editorial accompanying the study, Babesia infection -- babesiosis -- is now considered an "emerging infectious disease" in the U.S. The new report, led by CDC researchers, found that there were 159 transfusion-related cases in the country from 1979-2009.

A small minority of cases appeared in the first ten years of the study, while the vast majority occurred between 2000 and 2009, indicating a rise in babesiosis spread through transfusions. The authors suggest, however, that more cases probably exist than are reported, since doctors may not often realize that what they're dealing with is Babesia. Many cases are misdiagnosed as malaria, which is another red blood cell infection.

Some infected people have no symptoms while others may show fever, headache, chills, drenching sweats, muscle pain, malaise, and hemolytic anemia, which is when red blood cells die too early. Most severe cases develop in people without spleens, and in others with compromised immune systems, such as the elderly, newborns, and infants. In very bad cases, patients can experience organ failure, heart attack, red blood cell breakdown, and even death.

"We want clinicians to become more aware of babesiosis, including the small possibility of transmission via blood transfusion," says lead author Barbara Herwaldt, M.D., M.P.H., a medical epidemiologist with the CDC. "If a patient develops unexplained fever or hemolytic anemia after a transfusion, babesiosis should be considered as a possible cause, regardless of the season or U.S. region."

Babesia infection via tick bites is most common in the Northeast and Midwest, though a related infection has been seen in California and Washington state. Bites occur year-round, though they tend to spike during the summer months.

The authors call for better screening methods to be used for transfused blood. Currently there is no FDA-approved blood test for donor blood, which the authors say should quickly be addressed. Of course, preventing tick bites from occurring in the first place is an even better method for prevention.

The study and accompanying editorial were published in the September 5, 2011, online issue of Annals of Internal Medicine.

Image: Wikimedia Commons.

This article originally appeared on

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Alice G. Walton, PhD, is a health journalist and an editor at The Doctor Will See You Now.

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