First documented human Rickettsia aeschlimannii infection. (Letters).

To the Editor: Rickettsia aeschlimannii, which was first isolated from Hyalomma marginatum ticks collected in Morocco in 1997 (1), has also been found in H. marginatum ticks from Zimbabwe, Niger, and Mali (2). For the past 3 years, we have included this species in the panel of rickettsiae for which sera from patients with suspected tickborne diseases are routinely tested. This procedure allowed us to document, by polymerase chain reaction (PCR) amplification and serologic testing, the first case of R. aeschlimannii human infection, which occurred in a patient returning from Morocco.

This 36-year-old man traveled to Morocco in August 2000. On returning to France, he noticed a vesicular lesion of the ankle, which became necrotic and resembled the typical "tache noire" of Mediterranean spotted fever (3). He became ill with fever of 39.5[degrees]C and a generalized maculopapular skin rash. Laboratory tests showed a normal blood cell count but moderately increased transaminases. An early serum specimen was tested to confirm the diagnosis of Mediterranean spotted fever. By microimmuno-fluorescence, the patient's serum had immunoglobulin G and M titers of 1:32 and 1:16, respectively, against R. aeschlimannii; 0 and 1:16 against R. conorii, R. africae, R. slovaca, R. helvetica, and R. massiliae; and 0 and 1:8 against "R. mongolotimonae." Western blot results showed that the patient's serum reacted more intensively with R. aeschlimannii proteins than with those of the other tested rickettsiae. Attempted PCR amplification of a 630-nt portion of the rickettsial ompA gene (nt 70 to 701) (4) from the early serum specimen yielded a product of the expected size. The sequence of this amplicon allowed the identification of R. aeschlimannii with 100% homology. The patient was treated with doxycycline, 200 mg daily for 1 week, and rapidly recovered.

This case is the first documented infection caused by R. aeschlimannii, a Rickettsia that had been isolated only from Hyalomma marginatum ticks from Africa. In our patient, its pathogenic role was demonstrated by PCR, a technique that has also proven useful in identifying other new rickettsial diseases, including infections with R. helvetica (5), R. slovaca (6), and R. felis (7). The serologic findings indicated antibodies at a higher level to R. aeschlimannii than to other tested species. R. aeschlimannii is phylogenetically distant from R. conorii but is closely related to R. rhipicephali and R. montanensis, which have never been described as human pathogens. This patient appeared to have a typical case of R. conorii infection, with seasonal and geographic characteristics favoring this diagnosis (3). This case was clinically and epidemiologically mistaken for R. conorii infection, suggesting that R. aeschlirnanii may be another cause of Mediterranean spotted fever in Morocco.

The systematic identification of rickettsial species in human infections continues to increase the number of recognized human pathogens (3). This finding has demonstrated once again that more than one species or serotype of tick-transmitted rickettsia may be prevalent in the same area, as observed, for example, with R. slovaca, "R. mongolotimonae," and R. conorii in southern France (3); R. africae and R. conorii in sub-Saharan Africa (8); and R. conorii and Israeli spotted fever rickettsia in Sicily and Portugal (9). Rickettsia species first identified in ticks should be considered as potential human pathogens, as all recently described tick-transmitted rickettsiae pathogenic for humans were initially found in ticks and were considered nonpathogenic for several years (3).

Didier Raoult, * Pierre-Edouard Fournier, * Philippe Abboud, ([dagger]) and Frangois Caron ([dagger])

* Unite des Rickettsies, Universite de la Mediterranee, Marseille, France; and ([dagger]) Service de Maladies Infectieuses, Centre Hospitalier Universitaire de Rouen, Rouen, France

References

(1.) Beati L, Meskini M, Thiers B, Raoult D. Rickettsia aeschlimannii sp. nov., a new spotted fever group rickettsia associated with Hyalomma marginatum ticks. Int J Syst Bacteriol 1997;47:548-54.

(2.) Parola P, Raoult D. Ticks and tickborne bacterial diseases in humans: an emerging infectious threat. Clin Infect Dis 2001;32:897-928.

(3.) Raoult D, Roux V. Rickettsioses as paradigms of new or emerging infectious diseases. Clin Microbiol Rev 1997;10:694-719.

(4.) Roux V, Fournier PE, Raoult D. Differentiation of spotted fever group rickettsiae by sequencing and analysis of restriction fragment length polymorphism of PCR amplified DNA of the gene encoding the protein rOmpA. J Ciin Microbiol 1996;34:2058-65.

(5.) Nilsson K, Lindquist O, Pahlson C. Association of Rickettsia helvetica with chronic perimyocarditis in sudden cardiac death. Lancet 1999;354:1169-73.

(6.) Raoult D, Berbis P, Roux V, Xu W, Maurin M. A new tick-transmitted disease due to Rickettsia slovaca. Lancet 1997;350:112-3.

(7.) Raoult D, La Scola B, Enea M, Fournier PE, Roux V, Fenollar F, et al. Isolation and characterization of a flea-associated rickettsia pathogenic for humans. Emerg Infect Dis 2001;7:73-81.

(8.) Raoult D, Fournier PE, Fenollar F, et al. Rickettsia africae, a tick-borne pathogen in travelers to sub-Saharan Africa. N Engl J Med 2001;344:1504-10.

(9.) Bacellar F, Beati L, Franca A, Pocas J, Regnery R, Filipe A. Israeli spotted fever rickettsia (Rickettsia conorii complex) associated with human disease. Emerg Infect Dis 1999;5:835-6.