FIG. 2.

Rickettsial infection density in fleas fed an R. felis–infected blood meal 7–28 dpe. The R. felis infection density was determined by quantitative real-time polymerase chain reaction of individual cat flea samples. Bars represent the mean (±standard error of the mean) Rf17kDa/Cf18S ratio of three experimental groups exposed to identical R. felis exposure meals for 1 day and assessed at weekly intervals in two replicate trials. Mean R. felis infection density was 0.54 and 0.57 in trials 1 and 2, respectively, and significantly greater density was observed in fleas sampled at later time points. *Significant difference from 7 dpe.