Rat and flea conditions in a rural endemic plague area in Kenya

Extract

The female percentage figures for Rattus for the three years are 57.8, 57.7 and 57.5 respectively. Pregnancy records were obtained by counting embryos sufficiently advanced to be recognizable to the naked eye. The average number of embryos per pregnant female agree closely for the three years, and the error of underestimating invisible embroys appears to be constant. There is a slight suggestion of two enhanced breeding periods for Rattus in the area, both periods being coincident with higher rainfall and the growing season. The main interest in these figures lies in the large number of embryos recorded over the nipple provision, the greatest number observed being seventeen.

The average number of fleas per rat shows that the period of their maximum incidence agrees closely with the higher incidence of plague.

The number of traps set out daily in huts has remained constant over the three years. Little reliance could be placed on detailed trapping figures as the trapping varies considerable from village to village and even hut to hut, and gross figures only can be employed. Not only do these figures demonstrate that endemic areas have a much higher Rattus density and higher breeding rates than plague-free areas, but they indicate that the incidence of plague, both in man and rats, is more closely associated with rat population densities than any other factor.