Table 2.

Summary of fleabite challenges

MouseMice bitten by fleas infected with:
Wild type
Δpla
Δpla (complemented)
Infective fleabitesOutcomeInfective fleabitesOutcomeInfective fleabitesOutcome
11B6S3B
22B6S5B
32B3S7B
46B38B
59B48B
610B512B
73S56S
810S611S
9688
10799
Median65.58
  • Shown is the cumulative number of bites from infective fleas, which had the characteristic bacterial blockage of the proventricular valve in the flea foregut that is prerequisite for efficient transmission (see refs. 4 and 38). The median number of infective bites received by each group was not significantly different (P > 0.6 by Mann–Whitney test). B, bubonic plague; S, primary septicemic plague; —, no disease. Disease type and outcome were significantly different for the Δpla group compared with the other two (P < 0.05 by χ2 test).