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Preventing Transfusion Transmitted Babesiosis

Babesiosis is a tickborne zoonotic disease that is caused primarily by Babesia microti in the United States. Babesia is endemic in New England and regions of the upper Midwest. In recent years, babesiosis has been increasingly transmitted blood transfusions. The incubation period for transfusion-related babesiosis ranges from 11 to 176 days (median, 37 days), and the diagnosis is often made unexpectedly, after a routine blood-smear examination.

The clinical manifestations of B. microti infection range from asymptomatic infection to severe disease resulting in hemolysis, shock, and death. The risk of severe infection is particularly high among patients who do not have a functional spleen or are immunocompromised. Symptoms such as fatigue, malaise, weakness, fever, nausea, anorexia, myalgias, abdominal pain, and diarrhea are frequently reported. Abnormal laboratory test results, such as thrombocytopenia, hemolytic anemia, and elevated aminotransferase and serum alkaline phosphatase levels, may occur, but none of these results are highly sensitive for the diagnosis of babesiosis.

During 2010–2014, babesia species were responsible for 4 of the 15 deaths caused by transfusion-transmitted infections in the United States. Obtaining a donor history is largely ineffective in preventing transfusion-transmitted babesiosis, because 80% of infected persons are asymptomatic and may remain parasitemic for several months. In addition, babesia species survive in red cells that are stored in either liquid or frozen form. In regions in which babesia is endemic, approximately 1 to 2% of blood donors have laboratory evidence of current or past infection, with the prevalence reaching 10% in some hyperendemic areas. Currently, donors are deferred if they have a history of babesiosis or have been implicated in a case of transfusion-transmitted babesiosis. No laboratory tests are currently licensed for donor screening.

A recent study reported that screening blood donations for Babesia microti using both antibody and DNA based tests significantly reduced the risk of transfusion transmitted infection. The study was undertaken in four states (Connecticut, Massachusetts, Minnesota, and Wisconsin) where Babesia is endemic. A total of 89,153 donations from 60,512 donors were screened by PCR to detect Babesia microti DNA and an arrayed fluorescent immunoassay to detect IgG antibodies. Confirmatory testing was performed with IgG and IgM Western blots and quantitative PCR.

A total of 335 of the 89,153 blood donation samples (0.38%) were confirmed to be posi- tive. Of these 335 positives, 9 samples were PCR positive and antibody negative, 67 (20%) were PCR positive and antibody positive and 259 were PCR negative and antibody positive. PCR-positive samples were identified all through the year while antibody-negative infections occurred from June through September.

The Food and Drug Administration’s Blood Products Advisory Committee recommended universal babesia antibody screening in May 2015. The current study suggests that both antibody and PCR testing may be required to prevent transfusion transmitted babesiosis.

Manian FA et al. Case 27-2016 — A 71-Year-Old Woman with Müllerian Carcinoma, Fever, Fatigue, and Myalgias. N Engl J Med 2016; 375:981-991September 8, 2016DOI: 10.1056/NEJMcpc1607091

Moritz ED et al. Screening for Babesia microti in the U.S. Blood Supply. N Engl J Med. 2016;375:2236-45

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