Rickettsia felis infection in man, France.

To the Editor: In August 2008, a 64-year-old man was admitted to the Salon-de-Provence Hospital, France. He had fever (39°C) and a maculopapular rash. No eschars or adenopathy were noted. The patient had a relatively mild illness; the only abnormal laboratory values were elevated aminotransferase levels (aspartate aminotransferase 85 U/L and alanine aminotransferase 135 U/L). The man was an agricultural worker who had originated from Algeria but at this time lived in a shelter in southern France. His potential for contact with dogs in his environment was noted, but no history of flea exposure was elicted. This disease was postulated to be rickettsiosis because no other cause for his fever and rash was evident. Doxycycline was then administered, and the patient rapidly improved.

Serum testing at the Unité des Rickettsies (Marseilles, France), using a multiple-antigen immunofluorescent assay (

Rickettsiae were first described in the cat flea (

, ticks, and mites; however, the only currently recognized vector is the C. felis flea (). The reported hosts for these vectors are mainly cats, dogs, and rodents. R. felis is the only SFG species that is transmitted by fleas. Studies have confirmed that R. felis in C. felis flea populations is mostly maintained by transstadial and transovarial transmission (). Levels of R. felis infestation in C. felis fleas are variable, and the specific mechanisms of maintenance within each flea remain unknown. Prevalence is increased by fleas feeding on mammalian hosts infected with R. felis. Nevertheless, the precise relationship between the vector and the host remains unknown, and the mechanisms of rickettsial replication have not yet been examined ().

We searched PubMed and found reports (case reports and seroprevalence studies) of 68 R. felis infections. Cases have been reported in the Americas, Asia, Tunisia, and Europe (Technical Appendix). Such clinical cases rarely occur in warm countries, unlike the worldwide distribution of the bacteria, mentioned above. Reports of human infection with R. felis are rare, but the organism is frequently isolated from fleas.

We summarized the available clinical findings for 34 persons infected with R. felis: 32 had fever; 24, cutaneous rash (mostly maculopapular); 4, cutaneous eschar; 5, neurologic signs; 7, digestive symptoms; 3, cough without pneumonia; and 2, pneumonia. Clinical findings for R. felis are often confused with those found for patients with murine typhus or other febrile illnesses, and they appear to be more complex and more severe than initially thought.

Western blot after cross-adsorption with (left to right) Rickettsia conorii, R. massiliae, R. felis, and R. aeschlimannii. When cross-adsorption is performed with R. felis, the specific antigen-corresponding line disappears, which indicates R. felis as the causative microorganism.

Technical Appendix

Rickettsia felis Infection in Man, France