Abstract
Studies were carried out on the lethal susceptibility of mice to L. icterohaemorrhagiae. The following results were obtained. 1. Three-day-old mice were lethally susceptible to L. icterohaemorrhagiae at 100% lethality. Five- to 7-day-old mice were also susceptible at high lethalities and at 100% infectivity. 2. Three-day-old mice were protected from the lethal effect of leptospirae by specific anti-serum. No surviving mice, however, were prevented from the leptospiral infection of the kidneys. 3. It was estimated that 1 leptospira was infective to the mouse, but that at least 100 leptospirae were required to display lethal effect on 3-day-old mice. 4. The susceptibility of adult mice to L. icterohaemorrhagiae was enhanced by gammairradiation of the mice. The availability of mice to the leptospiral experiment or the routine use for the virulence titration, neutralization test, and the maintenance of the pathogenic strain was discussed.
