Relationship between tick bites and the seroprevalence of Babesia microti and Anaplasma phagocytophila (previously Ehrlichia sp.) in blood donors.

Abstract

Tick-borne diseases, particularly babesiosis and ehrlichiosis, represent recently emerging infections. Despite an increased recognition of the threat tick-borne agents pose to blood safety, our understanding of the prevalence and transmissibility of these agents in blood donors is limited. Babesia microti and Anaplasma phagocytophila (previously Ehrlichia sp.) seroprevalence was determined in random Connecticut and Wisconsin donors, and subsequently in Connecticut donors reporting tick bites. In the interim, a postcard survey regarding tick bites during the previous 6 months was sent to 6,000 random donors in six geographically distinct collection regions. In total, 3 of 999 Wisconsin donors (0.3%) and 6 of 1,007 Connecticut donors (0.6%) had antibodies to B. microti. Of 992 donors tested for A. phagocytophila, 5 Wisconsin donors (0.5%) and 35 Connecticut donors (3.5%) were seropositive. A total of 2,482 donors (41.4%) completed the survey; 103 (4.1%) reported a tick bite. Of 848 Connecticut donors (0.4%) reporting tick bites, 3 had B. microti antibodies, while 8 (0.9%) had A. phagocytophila antibodies. These rates were not significantly different from control donors. Blood donors seropositive for B. microti and A. phagocytophila are present in Connecticut and Wisconsin. Donors readily recall previous tick bites, but self-reported bites are not reliable indicators of serologic status. The exposure of blood donors to tick-borne pathogens does suggest a need to better understand the transfusion transmission potential of these agents.