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

Evan M. Bloch, Zakayo Mrango, Mabula Kasubi, Jerusha Weaver, Aleksandra Mihailovic, Beatriz Munoz, Anna Weimer, Andrew Levin, Laura Tonnetti, Jeffrey M. Linnen, Vanessa Brès, Douglas E. Norris, Giovanna Carpi, Sheila K. West

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Background Babesia, 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 findings A 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 <15yrs (n = 266) underwent a RDT for Plasmodium and assessment by ELISA for B. microti antibodies. A total of 570 subjects participated (mean age 22 [<1 to 90yrs]) of whom 50.7% were female and 145 (25.5%) subjects were Plasmodium RDT positive (+). In those <15yrs, the median ELISA S/CO was 1.11 (IQR 0.80-1.48); the median S/CO in the case (n = 120) and control (n = 146) hamlets was 1.19 (IQR 0.81-1.48) and 1.06 (IQR 0.80-1.50) respectively (p = 0.4). Children ≥5yrs old were more likely to have a higher S/CO ratio than those <5yrs old (p<0.001). One hundred (38%) subjects <15yrs were Plasmodium RDT+. The median S/CO ratio (children <15yrs) did not differ by RDT status (p = 0.15). In subjects ≥15yrs, no molecular test was positive for Babesia, but four subjects (1.4%) were IFA reactive (two each at titers of 128 and 256). Conclusions/Significance The findings offer further support for Babesia in rural Tanzania. However, low prevalence of seroreactivity questions its clinical significance.

Original languageEnglish (US)
Article numbere0007632
JournalPLoS neglected tropical diseases
Issue number8
StatePublished - 2019

ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health
  • Infectious Diseases


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