Molecular identification of Rickettsia typhi and R. felis in co-infected Ctenocephalides felis (Siphonaptera: Pulicidae).

Rickettsia typhi and R. felis, 2 closely related rickettsial species, often have been identified in cat fleas, Ctenocephalides felis (Bouché) from the same geographical location. However, no fleas have been found to be naturally infected concurrently with both rickettsial species. To examine whether one rickettsial species can develop simultaneously with another species in the same flea host, cat fleas, naturally infected with R. felis, were allowed to feed on blood containing R. typhi (Ethiopian strain, 10(7) PFU/ml). Experimental controls consisted of uninfected cat fleas, fleas infected with only R. typhi; and fleas naturally infected with only R. felis. After 9 d at 28 degrees C, the fleas were examined by PCR amplification and subsequent restriction digest analysis and dot blot hybridization of PCR products. Results from these studies demonstrated that R. felis and R. typhi are capable of co-existing in the same flea host. Subsequent isolation of R. typhi from dually infected fleas by tissue culture indicated that R. typhi was viable and capable of being maintained in fleas naturally infected with R. felis. As more studies confirm the presence of R. felis and R. typhi in domestic pets and peridomestic vertebrates in urban areas, the ability of the individual cat fleas, which live on these animals, to support both rickettsial species could be an epidemiologically important consideration.