Studies on the exoerythrocytic stages of simian malaria. VIII.

Abstract

Exoerythrocytic schizonts of Plasmodium knowlesi were found in liver tissue acquired every 8 hr between 48 and 136 hr following intrahepatic inoculation of Macaca mulatta monkeys with sporozoites from Anopheles balabacensis balabacensis mosquitoes. Development was completed as early as 112 hr after inoculation as evidenced by presence of parasites in the peripheral circulation. This paper, the eight in a series on the exoerythrocytic (EE) stages of simian malaria, describes the EE stages of Plasmodium knowlesi in the liver of the Macaca mulatta monkey. Plasmodium knowlesi was originally de- scribed by Sinton and Mulligan (1932, 1933) from material supplied by Knowles and Das Gupta (1932) and their own isolate from a M. irus (= fascicularis) monkey obtained from Singapore. It is unique among the primate malarias in being the only species with a quotidian asexual cycle in the blood. Next to P. cynomolgi, it is probably the most widely used simian malaria for chemotherapeutic and immunologic studies. The only previous de- scription of the EE forms of P. knowlesi was by Garnham et al. (1957); the earliest forms seen were in biopsy material taken 92 hr after inoculation of sporozoites. Reported here are the results of studies to determine the rate of growth of the EE forms of this parasite beginning 48 hr after sporozoite inoculation and to describe forms at various intervals in the developmental cycle in the liver tissues.