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J Travel Med. 2018 Jan 1;25(1). doi: 10.1093/jtm/tax073.

Case report of the patient source of the Babesia microti R1 reference strain and implications for travelers.

Author information

Institute of Virology, Parasitology Unit, University of Marburg, Marburg, Germany.
Department of Internal Medicine, Section of Gastroenterology and Infectious Diseases, University Hospital Gießen and Marburg, Marburg, Germany.
Internal Medicine Department, Centre Hospitalier Bretagne Atlantique, Vannes, France.
Microbiology Department, Centre Hospitalier Bretagne Atlantique, Vannes, France.
Dynamique des Interactions Membranaires Normales et Pathologiques, UMR5235 CNRS, Université Montpellier, Montpellier, France.
Department of Internal Medicine, Section of Infectious Diseases, Yale School of Medicine, New Haven, CT, USA.
Yale School of Public Health and Yale School of Medicine, 60 College St., New Haven, CT 06520, USA.
Institut de Biologie Computationnelle (IBC), Montpellier, France.
Institut de Recherche en Cancérologie de Montpellier (IRCM - INSERM U1194), Institut régional du Cancer Montpellier (ICM) & Université de Montpellier, France.



In 2002, a previously healthy 69-year-old man travelled to France from the United States and presented to our hospital with a febrile illness that subsequently was determined to be babesiosis. The blood isolated from this patient served as a source for propagation of the Babesia microti R1 strain with subsequent sequencing and annotation of the parasite genome.


Upon admission, we obtained a medical history, performed a physical examination, and examined his blood for the presence of a blood borne pathogen by microscopy, PCR and indirect immunofluorescence antibody testing. Once the diagnosis of babesiosis was made, we reviewed the literature to assess the distribution of B. microti-associated babesiosis cases in immunocompetent patients from outside the USA.


The patient recalled a tick bite during the previous month on Cape Cod, Massachusetts. The diagnosis was confirmed by identification of Babesia-infected red blood cells on blood smears, amplification of B. microti DNA in blood by PCR and the presence of B. microti antibody in the serum. This strain was the first isolate of B. microti to be fully sequenced and its annotated genome serves as a reference for molecular and cell biology studies aimed at understanding B. microti pathophysiology and developing diagnostic tests and therapies. A review of babesiosis cases demonstrates a worldwide distribution of B. microti and identifies potential emerging endemic areas where travelers may be at risk of contracting B. microti infection.


This case provides clinical information about the patient infected with the R1 isolate and a review of travel risk, diagnosis and treatment of babesiosis in endemic and non-endemic areas.


Babesia microti; Babesiosis; R1 strain; tick-borne disease


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