Rickettsia felis infection rates in an east Texas population.

Murine typhus (Rickettsia typhi), endemic in southern California and South Texas, is maintained within a host-vector system consisting of the opossum and cat flea. In the early 1990s, a second rickettsial species, Rickettsia felis, was also found to be maintained within the opossum-cat flea system and is, in fact, found more commonly than R. typhi in the opossum and cat flea. Recognized as a human pathogen in 1994, R. felis causes an infection that produces symptoms indistinguishable from classic murine typhus caused by R. typhi. Just how frequently "murine" typhus is caused by R. felis versus R. typhi is uncertain. By using a recombinant antigen specific for R. felis, 148 human serum samples were assayed for the presence of antibodies specific for R. felis. Results indicated that out of 32 samples that were positive when run against R. typhi, only 3 were also positive for R. felis. Thus, we conclude that R. felis infections are rare in Texas and most murine typhus is due to R. typhi infection.