Rickettsia Mooseri Infection in the Fleas Leptopsylla Segnis and Xenopsylla Cheopis

Genetic characterization and transovarial transmission of a typhus-like rickettsia found in cat fleas.

“…The samples of cat fleas obtained in 1985 and 1989 were from a commercial colony maintained by El Labs, Soquel, CA (ELB), from a laboratory colony maintained at the University of Maryland at Baltimore (UMAB), and from the American Biological Supply, Baltimore (ABS). Control fleas were C. felis and Xenopsylla cheopis fleas that were infected with the Ethiopian strain of Rickettsia typhi (AZ332) as described (12).…”

“…with 0.2 ml of flea homogenates (pool = 10 fleas per 1 ml of brain heart infusion broth). Inoculated animals (three animals per flea pool) were observed for 28 days, and seroconversion was measured by the indirect immunofluorescent antibody test to measure specific antibodies to R. typhi in serum as described (12).…”

“…The presence of R. typhi in ELB fleas was determined by DFA and ELISA tests. In DFA the smears of 30 newly emerged unfed fleas were stained with fluorescein isothiocyanate-labeled anti-R. typhi (convalescent) guinea pig serum (12). A double sandwich antigen-capture ELISA test using two monoclonal antibodies (T65-lG9.3 and T66-1E8.1) with specificity for R. typhi was also used as described (13).…”

Epidemiology of Murine Typhus

“…Within the cytoplasm of the midgut cells, the rickettsiae replicate by transverse binary fission and are released in the gut lumen and subsequently excreted with the feces. When X. cheopis was allowed free access to rickettsemic hosts for 16 to 32 hours, there was a nearly 100% infection rate when assayed by direct fluores cent antibody (DFA) test (26,27). Usually, rickettsiae in the gut epithelial cells of infected fleas cannot be detected until 3-4 days following infectious feeding.…”

“…R. typhi tends to escape from the host cell very early in the growth cycle without damaging it (58) and the rickettsiae can spread to the entire midgut lining within 7-9 days after an infectious feeding (26,27). Although most of the epithelial cells have con tained masses of R. typhi by day 10 postinfection, the intensity of the involvement of these cells varied (27). Ito et al (31) noted that some cells were packed with clumps of rickettsiae while others had scattered and fewer organisms.…”