Transfusion-transmitted babesiosis in Rhode Island.

BACKGROUND: Babesiosis is caused by an intraerythrocytic protozoan transmitted by ticks. Blood transfusion is another mode of transmission.

STUDY DESIGN AND METHODS: This was a retrospective study based on babesiosis cases reported to the Rhode Island Department of Health between 1999 and 2007. Additional cases were also identified.

RESULTS: Twenty-one cases of transfusion-transmitted babesiosis (TTB) were identified from 1999 through 2007. From 2005 through 2007, the incidence approached one case per 9000 units of blood transfused. One of 21 (5%) TTB cases was diagnosed in July, in sharp contrast to 65 of 152 (43%) of the total babesiosis cases diagnosed during July in Rhode Island. Many cases were identified when a complete blood count with a differential was routinely requested and parasites were noted by laboratory technologists. Most patients with TTB had underlying conditions known to predispose to symptomatic infection.

CONCLUSION: Blood transfusion is an important mode of Babesia transmission. The current screening method of omitting donors with a history of babesiosis may be effective in preventing some, but not all, cases of TTB and current processing of blood products does not eradicate this parasite. Thus, a better screening test is needed. Alternatively, pathogen reduction technology could be utilized to prevent this mode of transmission.