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

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

doi:10.1371/journal.pntd.0007632

Abstract

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 <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/SignificanceThe findings offer further support for Babesia in rural Tanzania. However, low prevalence of seroreactivity questions its clinical significance.

Highlights

Babesia is a ubiquitous [1, 2] genus of intraerythrocytic, apicomplexan parasites, that is increasingly recognized as posing risk to human health
A family of tick-borne parasites, causes babesiosis, a disease that is very similar to malaria
We conducted a study of two rural communities in Tanzania where earlier findings had suggested Babesia was present

Summary

Introduction

Babesia is a ubiquitous [1, 2] genus of intraerythrocytic, apicomplexan parasites, that is increasingly recognized as posing risk to human health. In the case of B. microti, its principal vector, Ixodes scapularis (the blacklegged or deer tick), transmits Borrelia burgdorferi (Lyme disease), Anaplasma phagocytophilum (human granulocytic anaplasmosis) and Borrelia miyomotoi (relapsing fever). Babesiosis, the clinical disease named for infection with any of the Babesia species, is frequently uneventful in the immunocompetent human host following a mild, self-limiting or even subclinical course. Symptoms, when they do occur, are those of mild flu-like illness (e.g. fever, myalgia, fatigue, headache and chills). A tick-borne genus of intraerythrocytic parasites, is understudied in humans outside of established high-endemic areas. A pilot study suggested that Babesia was present in a rural district of Tanzania

Results

Discussion

Conclusion