Project: Research project

Project Details


Babesiosis is emerging as a disease of public health significance in the
U.S.A. with increased reports of clinical, even fatal, cases in areas
where the risk of infection with Babesia was not recognized previously.
The potential importance of these hemoprotozoal parasites is also
evidenced by the increased risk of tick-transmitted Babesia in Lyme
disease endemic areas and the enhanced susceptibility of patients with
human immunodeficiency virus infections to severe babesiosis. Until
recently, human babesial infections in this country have been attributed
to B. microti, derived from rodents. The proposed project is designed
to investigate two hypotheses. The preliminary hypothesis is that human
babesiosis in the U.S.A. may be caused by babesial parasites that are
antigenically and genotypically distinct from B. microti. To investigate
this possibility, Babesia will be isolated from asymptomatic carriers,
primarily in Lyme disease endemic areas, and from patients with clinical
babesiosis. The isolates will be characterized and compared molecularly
to morphologically similar Babesia isolates from humans and animals in
other geographic locations. The emphasis of our studies will focus on
parasites that represent genotypically distinct isolates, are
particularly virulent in humans and/or were isolated from a patient after
recovery from clinical disease or from an asymptomatic carrier. Isolates
selected by these criteria will be utilized to test the primary
hypothesis, which is that small babesial parasites, such as B. microti
and other human babesial isolates in the U.S.A., may have an
exoerythrocytic developmental stage, which if like the intralymphocytic
schizont stage of Theileria, would be capable of inducing host cell
transformation and proliferation. To evaluate this possibility, tissues
from babesiosis patients and hamsters infected by tick-transmission of
human babesial isolates will be examined for the presence of
exoerythrocytic parasite stages. Selected tissues with
lymphoproliferative foci and/or potential intracellular parasites will
be evaluated further by in situ hybridization of fluorescent-labelled,
Babesia-specific ss-rDNA probes. In vitro cultivation techniques
developed for the maintenance of Theileria schizont-infected
lymphoblastoid cell will be employed to isolate similar stages in the
blood and/or lymphoid tissues of humans and hamsters with tick-derived
Babesia infections. In addition, the infectivity of tick-derived
babesial sporozoites for human mononuclear cells in vitro will be
determined. The proposed study will provide valuable information about
the basic biology of these Babesia parasites and methodology which can
be applied to improve the diagnosis and control of human babesiosis.
Effective start/end date7/1/936/30/99


  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health


  • Medicine(all)
  • Immunology and Microbiology(all)


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