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Journal of Clinical Microbiology, June 2001, p. 2178-2183, Vol. 39, No. 6
School of Veterinary Medicine, Rakuno-Gakuen
University, Ebetsu 069-8501,1 Hoygo Red
Cross Blood Center, Kobe 651-0062,2
Third Division of the Department of Medicine,
Kobe University School of Medicine, Kobe
650-0017,3 and Kyoto Prefectural
University of Medicine, Kyoto 602-8566,4
Japan, and Harvard School of Public Health, Boston,
Massachusetts 021155
Received 16 January 2001/Returned for modification 20 March
2001/Accepted 2 April 2001
To determine the source of infection for the Japanese index case of
human babesiosis, we analyzed blood samples from an asymptomatic individual whose blood had been transfused into the patient. In addition, we surveyed rodents collected from near the donor's residence. Examination by microscopy and PCR failed to detect the
parasite in the donor's blood obtained 8 months after the donation of
the blood that was transfused. However, we were able to isolate
Babesia parasites by inoculating the blood sample into SCID mice whose circulating red blood cells (RBCs) had been replaced with human RBCs. A Babesia parasite capable of
propagating in human RBCs was also isolated from a field mouse
(Apodemus speciosus) captured near the donor's
residential area. Follow-up surveys over a 1-year period revealed that
the donor continued to be asymptomatic but had consistently high
immunoglobulin G (IgG) titers in serum and low levels of parasitemia
which were microscopically undetectable yet which were repeatedly
demonstrable by inoculation into animals. The index case
patient's sera contained high titers of IgM and, subsequently,
rising titers of IgG antibodies, both of which gradually diminished
with the disappearance of the parasitemia. Analysis of the parasite's
rRNA gene (rDNA) sequence and immunodominant antigens revealed
the similarity between donor and patient isolates. The rodent isolate
also had an rDNA sequence that was identical to that of the human
isolates but that differed slightly from that of the human isolates by
Western blot analysis. We conclude that the index case patient acquired
infection by transfusion from a donor who became infected in Japan,
that parasitemia in an asymptomatic carrier can persist for more than a
year, and that A. speciosus serves as a reservoir of an
agent of human babesiosis in Japan.
0095-1137/01/$04.00+0 DOI: 10.1128/JCM.39.6.2178-2183.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Human Babesiosis in Japan: Isolation of
Babesia microti-Like Parasites from an Asymptomatic
Transfusion Donor and from a Rodent from an Area Where Babesiosis
Is Endemic
*
Corresponding author. Mailing address: School of
Veterinary Medicine, Rakuno-Gakuen University, 582-1 Bunkyodai-Midorimachi, Ebetsu 069-8501, Japan. Phone and fax:
81-11-386-3144. E-mail: tsuji{at}rakuno.ac.jp.
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