Induction of retarded exoerythrocytic schizonts by chloroguanide resulting in delayed parasitaemia of Plasmodium inui in Macaca mulatta

Three Rhesus monkeys inoculated with a large number of sporozoites of Plasmodium inui dissected from the salivary glands of infected mosquitoes, Anopheles dirus. Two of the monkeys (inoculated with 8.06 x 10(5) and 1.3 x 10(7) sporozoites, respectively) were treated with chloroguanide base 6 mg/(kg.d) x 4 d starting from 24 h after the inoculations and the other one (inoculated with 5.93 x 10(6) sporozoites) was not treated with chloroguanide as control. The primary parasitaemia attacks occurred in the former 2 monkeys were 31 and 25 d respectively after inoculation, while in the control was 7.5 d. Liver biopsies were done in all of the 3 monkeys, normal schizonts were seen in the control monkey on d 8 after inoculation, while none were detected in the 2 monkeys treated with chloroguanide. However, the retarded exoerythrocytic schizonts were found by indirect fluorescent antibody test (IFAT) in liver sections of the monkey inoculated with 1.3 x 10(7) sporozoites. Therefore, it is evident that moderate doses of chloroguanide retarded the formation of schizonts and thus delayed the primary parasitaemia.