dry. Pneumonic plague, not being spread by the flea, is not influenced by temperature in this way (see p. 344).[1]
Bionomics of the rat-flea.—In ordinary circumstances the rat-flea completes its developmental cycle in fourteen days to three weeks, but in warm, damp weather this may be shortened to ten days. The average life of a flea, apart from its host, is about ten days, but it is capable of remaining alive without food for two months, should the temperature of the
ŒS., Distended œsophagus containing fresh blood; P.C., obstructing mass of plague culture.
air be low at the time. In tropical temperatures the insect can harbour the plague bacillus without feeding on blood for forty-five days.
Apart from the very serious danger arising from vermin affected with chronic plague, which may hang about a house for a long time, it would appear that the house itself does not retain the infection for any length of time. The Plague Commission has shown that floors of cow-dung if contaminated with Bacillus pestis do not remain very infective for more
- ↑ Though it is possible to transmit plague experimentally by means of the human flea, Pulex irritans, yet this flea plays little or no part in the spread of plague at the present day.
