On the Naming of Rickettsiae after Paul Ehrlich
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On the Naming of Rickettsiae after Paul Ehrlich

Some months ago, the New York Times carried the report of an outbreak of a disease called ehrlichiosis, apparently due to infection by a tick-borne rickettsia. Few seemed to know why such an organism should have been named in honor of Paul Ehrlich, who had never worked on any microorganisms except (as a morphologist) to stain them when dead, or (as a pharmacologist) to develop therapeutic drugs to treat such diseases as trypanosomiasis and syphilis. Among all of the scientists associated with rickettsial nomenclature (Ricketts, Rocha-Lima, Cox, Prowazek, Cowdry, Wolbach, etc.), only Ehrlich was not a professional rickettsiologist. The search for an explanation of this honor given to Paul Ehrlich proved to be quite interesting.

According to Bergey’s Manual of Systematic Bacteriology, it was the American C. B. Philip who in 1956 gave the name Ehrlichieae to Tribe II of the family Rickettsiaceae of the order Rickettsiales (Tribe I is Rickettsieae, and Tribe III is Wolbachieae). 1 Within Tribe II are three genera: Ehrlichia, Cowdria, and Neorickettsia. Within the genus Ehrlichia are four species: E. canis, E. phagocytophila, E. equi, and E. sennetsu; and four other candidate species: E. bovis, E. ovina, E. kurlovi, and E. platys. [NOTE: Of these eight species only one, E. kurlovi, is named after an individual! We shall see below why this is so.] Most of these organisms infect and form inclusion [End Page 731] bodies in one or another of the blood cells of (usually) single species of animals. As Bergey’s Manual puts it, the genus Ehrlichia was “named after Paul Ehrlich, a German bacteriologist” (sic!). 2

It turns out that Philip had taken up the use of Ehrlich’s name in his revision of an earlier nomenclature of the order Rickettsiales. In 1945, the Russian rickettsiologist Sh. D. Moshkovsky had introduced a new nomenclature that included a family Ehrlichiaceae. 3 Philip accepted Moshkovsky’s use of Ehrlich’s name, but changed the family to a tribe, the Ehrlichieae. He did, however, retain Ehrlichia as the name of a genus.

But 1945 was not the first introduction of the name Ehrlich into bacteriological nomenclature. Rather, it was the same Moshkovsky who had published a paper in French in 1937, in which he discussed a rickettsial inclusion body in the monocytes of guinea pig blood, previously called “Kurloff bodies.” He attributed these inclusions to an organism that he proposed to name Ehrlichia kurlovi, “in honor of Paul Ehrlich, since it was in his laboratory that the first representatives of this group were discovered, and because he has contributed so much to the study of the morphology of the blood and of the agents of infectious diseases.” 4

It seems that in 1888 a Russian, Prof. Mikhail Georgiyevich Kurloff (later a noted balneologist!), worked with Ehrlich, who at the time was employed as a physician/scientist in the Charité Hospital in Berlin. (This must have been not long before Ehrlich left the Charité to travel on a rest cure to Egypt on account of his tuberculosis.) Ehrlich was still much involved with his studies on the staining qualities of blood cells and was very interested in anemias. Kurloff was apparently assigned to investigate the effects of splenectomy on blood cell formation in the guinea pig. In the course of these studies, he discovered that some guinea pig leukocytes contained atypical granules, and he published the observation the next year in the local Saint Petersburg magazine Vratch [Doctor]. 5 [End Page 732]

But how did the 1889 article by Kurloff come to be associated with rickettsia, since the title of his paper referred only to alterations in the blood of splenectomized animals? Nor was there any hint in the title as it appeared in Index Medicus that it involved the finding of inclusion bodies in leukocytes. 6 Indeed, the paper was mentioned in Ehrlich and Lazarus’s famous book Die Anaemie, but the granules described were assumed to be constitutive, like those of normal eosinophiles and basophiles; rickettsial inclusions had not yet been identified. 7 Only after the discovery of rickettsiae several decades later was the significance of their typical cytoplasmic...