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Babesiosis should be considered more frequently when diagnosing certain fevers
Herwaldt BL. Ann Intern Med [Published online ahead of print Sept. 5, 2011].
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Babesia microti cases occurred in 19 states, some of which were not the main regions where the infection is endemic, according to recent study results.
Researchers from several US institutions conducted a study of B. microti incidence rates to illuminate the frequency of transfusion-associated infections. Eligible case-patients had received transfusions from 1979 to 2009 and had post-transfusion Babesia infection diagnosed by 2010, according to the results. The researchers said potential case-patients were eligible if there was no evidence that another transmission route may have occurred and ineligible if all pertinent donors had tested negative for the infection.
The final analysis included 159 transfusion-associated B. microti cases. A donor was implicated in 136 (86%) of these cases. Red blood cell components were linked to most cases, and four cases were linked to whole blood–derived platelets.
Cases were observed in all four seasons and in 22 of the 31 years evaluated. However, 77% of cases occurred between 2000 and 2009.
Eighty-seven percent of cases occurred in the seven states where the infection most frequently occurs. However, cases occurred in 19 states overall, including three cases that occurred in the West.
The researchers said donor-screening strategies may reduce the risk for this infection. “Babesiosis should be included in the differential diagnosis of unexplained post-transfusion hemolytic anemia or fever, regardless of the season or US region,” they wrote.
Not emphasized nearly enough is the great severity and even mortality suffered by recipients of contaminated transfusions. The disease is usually caused by B.microti in the US that infects blood, especially from donors residing in the same regions endemic for Lyme disease and granulocytic anaplasmosis — the Midwest and Northeast — since all three etiologic parasites utilize the same tick vector. Hematologists are critical for rapid diagnosis as blood smears in severe cases demonstrate classical round or oval ring structures in red cells — often in more than 10% of them. In splenectomized individuals the disease may take several weeks of clindamycin/quinine infusions before cure is certain.
– Harry S. Jacob, MD, FRCPath(Hon)
HemOnc Today Chief Medical Editor
Disclosure: Dr. Jacob reports no relevant financial disclosures.
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