Experimental Murine Typhus Infection in the Cat Flea, Ctenocephalides Felis (Siphonaptera: Pulicidae)1

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Abstract
During the feeding process, the cat flea, Ctenocephalides felis, acquires Rickettsia mooseri (R. typhi), the etiological agent of murine typhus, just as readily as does the putative vector, Xenopsylla cheopis. The course of infection within the species of fleas is similar. Following the logarithmic growth stage of R. mooseri during the first 9 days after the infectious feeding, the rickettsial content of the infected flea remained within 105–106 plaque-forming units/flea. In frozen sections of infected fleas prepared on the 9th day, the midgut epithelial cells were packed with rickettsiae. Rickettsia mooseri was noted within the lumen of the proventriculus and of the foregut in 20% of the cat fleas tested on the 15th–17th days, suggesting that transmission by bite may sometimes occur. Growth of the rickettsiae within the flea proceeded at a much more rapid rate when fleas were maintained under ambient conditions of 24 and 30 °C than when they were kept at 18 °C. The survival rates of infected fleas corresponded with those of uninfected controls throughout the 21 days of experimentation. The pattern and intensity of the laboratory infection of R. mooseri in C. felis, the broad host range and multiple feedings of this flea, and its past history as a suspected vector all suggest that C. felis may play a significant role in transmitting murine typhus infection to man and other mammals.

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