RODENT MALARIA MODEL OF PLASMODIUM BERGHEI ANKA STRAIN FOR ANTIMALARIALS SCREENING: ITS ESTABLISHMENT AND USE

For the purpose of screening both suppressive therapeutic and causal prophylactic antimalarials, Plasmodium berghei ANKA strain-rodent system and P. berghei ANKA strain-Anopheles stephensi-rodent (C₅₇BL or ICR/JCL strain) system were established. The results obtained are summarized as follows.1. The inbred strains of mice (C₅₇BL, ICR/JCL, 615, SMMC/B, SMMC/C) and one outbred strain (Kunming strain) were all found to be very susceptible to infection by blood inoculation (dose: 1×10⁷ rbc infected with P. berghei ANKA strain), the infection rate being 100%. 2. After the 3 rd mice-to-mice passage of the parasite the salivary gland infection rate of the mosquitoes decreased markedly with each passage. The 4 th day of blood induced infection was found to be the best time to feed mosquitoes. Under certain conditions the salivary gland infection rate of the A. stephensi was shown to be 38.0±4.8%. 3. A very significant difference in susceptibility to sporozoite-induced infection among different strains of the test mice was observed. C₅₇BL and ICR/JCL strains which showed a susceptibility rate of 85～93%, survived as long as 20 days on the average after ip inoculation with sporozoites. Tests of a number of current antimalarials in this model using the "4-day suppressive test" of blood schizontocidal action and Peters's method for causal prophylactic action showed that the ED₅₀s of drugs like chloroquine. mefloquine, primaquine and pyrimethamine were similar to those reported by other authors and that the drugs' causal prophylactic activity and residual activity could be correctly differentiated in one model. These results suggest that this may be a dependable model for antimalarials screening.