The pathogenicity of a Philippine isolate of Naegleria sp. in mice: effects of dose levels and routes of infection.

The pathogenicity of a Philippine isolate of Naegleria sp. was evaluated using 3-4 week-old mice as experimental animals. Results showed that only the massive doses of 10(6) and 10(7) amebae/mouse inoculated intranasally could successfully establish ameba infection in the brain and cause death after 2-6 days. The effect of the ameba on the mortality rate of inoculated mice was dose-dependent. The amebae were recovered in the brain when inoculated through intracerebral and intranasal routes and in the lungs, liver, and intestines when administered through intranasal and oral routes. By intraperitoneal inoculation, recovery of amebae was positive in all major organs except in the heart. Intravenous inoculation resulted to positive recovery in the lungs, spleen, liver, and heart. Infectivity of the ameba isolate in major organs was route-dependent.