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Volume 9, Number 8—August 2003

Research

Molecular Characterization of a Non–Babesia divergens Organism Causing Zoonotic Babesiosis in Europe

Barbara L. Herwaldt*Comments to Author , Simone Cacciò†, Filippo Gherlinzoni‡, Horst Aspöck§, Susan B. Slemenda*, PierPaolo Piccaluga‡, Giovanni Martinelli‡, Renate Edelhofer¶, Ursula Hollenstein#, Giovanni Poletti‡, Silvio Pampiglione‡, Karin Löschenberger¶, Sante Tura‡, and Norman J. Pieniazek*
Author affiliations: *Centers for Disease Control and Prevention, Atlanta, Georgia, USA; †Istituto Superiore di Sanità, Rome, Italy; ‡University of Bologna, Bologna, Italy; §Clinical Institute of Hygiene of the University of Vienna, Vienna, Austria; ¶University of Veterinary Medicine of Vienna, Vienna, Austria; #University Hospital for Internal Medicine I, Vienna, Austria

Main Article

Figure 2

Panel of computer-generated electronic images of photomicrographs of Babesia-infected erythrocytes on a Giemsa-stained smear of peripheral blood from the patient who became infected in Austria. The electronic images were edited for uniformity of color, without changing the form or size of the organisms. The image on the far right shows a tetrad (Maltese-cross form). Three glass slides of the actual blood films have been deposited in the Oberösterreichisches Landesmuseum, Biologiezentrum, Linz (i

Figure 2. Panel of computer-generated electronic images of photomicrographs of Babesia-infected erythrocytes on a Giemsa-stained smear of peripheral blood from the patient who became infected in Austria. The electronic images were edited for uniformity of color, without changing the form or size of the organisms. The image on the far right shows a tetrad (Maltese-cross form). Three glass slides of the actual blood films have been deposited in the Oberösterreichisches Landesmuseum, Biologiezentrum, Linz (i.e., Biology Center of the Upper Austrian Museum, Linz), with the accession number 2002/9. The slides are labeled “Babesia sp. (EU1), patient 001, Austria, Krems Land, July 25, 2000.”

Main Article

1The issue of what constitutes a new or newly described species requires periodic reevaluation as the techniques for characterizing microbes improve. Although the advent of molecular biology/phylogeny has made it possible to characterize organisms more precisely, the issue of how large a genetic difference in a particular gene(s) constitutes a new or different species is controversial. Bacterial taxonomy is a much more active and advanced field (26,27) than that for characterizing protozoa, in part because of the increasingly large numbers of bacteria being proposed as new species and the challenges posed by such possibilities as genetic rearrangements. In the recommendations published in 2002 by an ad hoc committee that reevaluated the species definition for bacteria (26), scientists were encouraged to use the “Candidatus” concept (i.e., to propose candidates for newly described bacterial species) for organisms that had been well-characterized, including the sequencing of the small subunit RNA gene, but had not yet been cultured. As noted above, we have referred to the protozoan we characterized as EU1. We have not claimed it as a newly identified species, despite having complete, identical, and novel 18S rRNA sequences for the organism from two patients, who were separated in time and space, and having done the sequence analysis for the two cases in different countries. However, although the Candidatus concept per se does not formally exist now for protozoa, on the basis of the precedent from the field of bacterial taxonomy, we propose that EU1 be considered a candidate species. If additional evidence supports the conclusion that the organism indeed constitutes a newly described species of the Babesia genus, we would favor the name Babesia venatorum, which now does not constitute an official name. We chose this name because the patients whose cases we reported were avocational hunters; “venator” is the Latin word for “hunter” (“venatorum,” the plural genitive case, means “of the hunters”).

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