Babesiosis in the U.S. Blood Supply

Sep 14, 2011 | Jane Huston | Research & Policy

On 5 Sept. the Centers for Disease Control (CDC) revealed recently completed research indicating the parasitic infection babesiosis as a growing threat to the blood supply in the United States. The paper, authored by Dr. Barbara Herwaldt and published in the Annals of Internal Medicine, reported 162 cases of babesiosis transmitted through blood transfusion between 1979 and 2009; however, nearly 80% of those cases occurred between 2000 and 2009. Furthermore, while babesiosis has historically been present in the Northeast and upper Midwest areas of the US, cases can now be found across the country. Currently, there is no approved test to screen blood donors for babesiosis infection, nor is there a method for removing the parasite from infected blood products.

Babesiosis is an infection by the Babesia parasite, most often Babesia microti. Transmission traditionally occurs through bites by an infected Ixodes scapularis, more commonly known as the deer tick.  Babesia is most often carried by very young ticks, no larger than a poppy seed, and infected persons often do not notice or recall any bites. Once introduced to the human host, the parasites infect and destroy red blood cells (RBCs), potentially leading to a deficiency of RBCs known as hemolytic anemia. Symptoms of babesiosis generally resemble a flu-like illness, and can include fever, chills, sweats, headache, body aches, nausea, fatigue and loss of appetite. Many people infected with the parasite will not experience any symptoms. In severe cases, babesiosis can lead to malfunction of vital organs and death.

Effective treatment is available, and traditional prevention strategies include limiting exposure to deer ticks through clothing or bug repellent. However, with the newly revealed transfusion transmission and the lack of detection methods for blood products, there are currently no means of prevention from transfusion-transmitted infection. Babesiosis is the most frequently reported parasite acquired through blood transfusions, though still rare. To monitor the situation, as of Jan. 1, 2011 the CDC listed babesiosis as a notifiable disease. This means state health departments are encouraged to share information about cases, though the disease may not be a reportable condition in individual states.

The newly reported transmission route is important because of the potential severity of the disease in certain vulnerable populations, such as the elderly, immunocompromised, premature infants, those with other severe diseases or those without a normally functioning spleen. Additionally, due to movement of blood donors and blood products, many more people can now be considered at risk for the disease. According to CDC authorities, “findings underscore the year-round vulnerability of the U.S. blood supply—especially, but not only—in and near babesiosis-endemic areas.” To combat this potential epidemic, the CDC urged manufacturers to develop a screening test for Babesia infection to help prevent transfusion transmission.

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