NEW YORK (Reuters Health) - Since the end of 2005, the US Food and Drug Administration has received nine reports of deaths due to a parasitic infection called babesiosis transmitted by blood transfusions, following nearly a decade in which no cases were reported.

Babesiosis, caused by the parasite Babesia, is usually transmitted through the bite of a tick, the same tick responsible for Lyme disease, although transmission via blood transfusion has also been reported. The disease is hardest on the elderly and people with compromised immune systems.

Doctors should consider babesiosis in immunocompromised patients fever with a history of recent transfusion, Dr. Diane M. Gubernot at the FDA in Rockville, Maryland, and colleagues advise in a report in the medical journal Clinical Infectious Diseases.

Gubernot and colleagues queried FDA safety surveillance systems for trends in babesiosis reporting since 1997. Nine of 10 deaths they uncovered occurred between 2005 and 2008. The patient ages ranged from 43 to 88 years.

Most of the patients developed altered mental status, kidney failure, or respiratory distress, with symptoms appearing anywhere from 2.5 to 7 weeks following blood transfusion. Once symptoms developed, death followed within 5 to 17 days. Implicated blood donations were identified, and all donors tested positive for the infection.

In addition to the nine fatal cases, the number of reports of potential transfusion-transmitted Babesia infection and post-donation babesiosis rose from zero in 1999 to 25 in 2007.

Gubernot and her associates note that Babesia species can survive blood banking procedures, including freezing.

SOURCE: Clinical Infectious Diseases, January 1, 2009.

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