[Studies on the establishment of malarial animal model of short-term relapse. IV. Short-term relapse in rhesus monkeys infected with sporozoites of Plasmodium cynomolgi].

The present paper reports that the short-term relapse could be artificially made by the application of the experimental method, and thus we established the monkey model of the short-term relapse. According to the experimental design, when the parasitemia was detected in rhesus monkeys infected with sporozoites of Plasmodium cynomolgi, a combined therapy of pyronaridine 6 mg/kg body weight, artemether 10 mg/kg and chloroquine 20 mg/kg once daily for 3 days was carried out to clear the erythrocytic parasite and then the short-term relapse was observed in the animal follow-up for 100 days. The combined therapy was given again when relapse occurred. One onset of relapse occurred on 47 days after therapy in monkey M194 infected with sporozoites 11 x 10(3). In M195 infected with sporozoites 55 x 10(4), relapses occurred for 3 times on 30, 37 and 51 days respectively after medication, but during a follow-up period of 200 days, no relapse was shown in M192 and M193 infected with sporozoites 50 and 55 x 10(2), respectively. The results showed that the frequency of the short-term relapse was relative to the sporozoites inoculation, and sporozoites less than 11 x 10(3) were not suitable for making short-term relapse in animal model. No long term relapse could be seen in all the 4 monkeys until 400 days. Under existing conditions that the relapse was generally explained with hypnozoite assumption, the establishment of animal model of short-term relapse could be tenable.(ABSTRACT TRUNCATED AT 250 WORDS)