Feeding frequency influences colonization of the cat flea digestive tract by Y. pestis.
Fleas that took a single infectious blood meal that contained ~ 2x108 CFU/ml of Y. pestis were subsequently provided uninfected maintenance feeds at low frequency (twice weekly for 4h), moderate frequency (five times weekly for 4h), or high frequency (daily for 18-22h) according to the schedule shown in (A). Black and grey bars indicate the infectious and maintenance blood meals, respectively; and the width of the bar corresponds to the 4h or 18-22h feeding period. (B) The bacterial load in individual fleas from the low-, moderate-, and high-frequency groups was determined in samples of 10–20 fleas collected immediately after the 4h infectious blood meal (day 0) or at 7–28 days after infection. The low- and high-frequency groups fed on the same infectious blood meal prior to segregating them. Horizontal bars represent the mean CFU/flea; dotted lines indicate the limit of detection (40 CFU). The cumulative results of three independent experiments are shown (Day 0, n = 60; Day 7, n = 60; Day 14, n = 54, 60, 60); Day 28 n = 50, 60, 40). *p <0.05 by Student’s t-test (Day 0) or by Kruskal-Wallis test with Dunn’s multiple comparison (Day 7–28). (C) Infection rate (percentage of fleas from which CFUs were recovered) at different times after infection. The mean and range of 3 experiments are indicated; *p <0.0166 by chi-square test with Bonferonni’s post-test. (D) Cumulative mortality of infected fleas and uninfected control fleas at the end of the 28-day experiments. The mean and standard deviation of 2–3 experiments with each of the three feeding frequency groups are indicated (low, n = 312, 310; moderate, n = 292, 276; high, n = 184, 214; cumulative number of infected fleas and uninfected control fleas, respectively). *p <0.0055 by chi-square test with Bonferonni post-test; NS = not significant.
