The Babesia observational antibody (BAOBAB) study: A cross-sectional evaluation of Babesia in two communities in Kilosa district, Tanzania

BackgroundBabesia, a tick-borne genus of intraerythrocytic parasites, is understudied in humans outside of established high-endemic areas. There is a paucity of data on Babesia in Africa, despite evidence that it is regionally present. A pilot study suggested that Babesia was present in a rural district of Tanzania.Methodology/Principal findingsA cross-sectional study was conducted July-August 2017: residents in a case hamlet that had clustering of subjects with high signal-to-cut off (S/CO) ratios for antibodies against B. microti in the pilot study, and a control hamlet that had lacked significant signal, were evaluated for B. microti. Subjects aged ≥15yrs (n = 299) underwent clinical evaluation and household inspections; 10ml whole blood was drawn for Babesia transcription mediated amplification (TMA), B. microti indirect fluorescent antibody testing (IFA) and rapid diagnostic testing (RDT) for Plasmodium spp. Subjects aged Plasmodium and assessment by ELISA for B. microti antibodies. A total of 570 subjects participated (mean age 22 [Plasmodium RDT positive (+). In those Plasmodium RDT+. The median S/CO ratio (children Babesia, but four subjects (1.4%) were IFA reactive (two each at titers of 128 and 256).Conclusions/SignificanceThe findings offer further support for Babesia in rural Tanzania. However, low prevalence of seroreactivity questions its clinical significance.