Abstract
Except for falciparum-malaria, severe multiple infections are rather rare in usual human malarias. However, abnormally heavy multiple infections up to 8 ring forms in a single erythrocyte have sometimes been recorded in literatures. Such extreme cases are compared for their rate of multiple infections and parasitemia. By contrast, in simian malarias multiple infections are rather frequent, especially in Plasmodium eylesi, P. cynomolgi bastianellii, P. cynomolgi cyclopis, and P. gonderi. Reported cases of human infections with simian malaria have been reviewed and summarized as a table. Of about 25 species or subspecies of simian malarias, 10 have been reported to infect human beings as routes of natural, accidental, experimental, or therapeutical infections. Human infections with simian malaria parasites are generally characterized by severe or mild attacks with rare or low parasitemia. Surveys of "abnormal form"of human malarial cases in literatures are suggestive of the presence of some doubtful cases of simian malarial infection. In routine clinical examinations of blood smears for malaria,it is rather impossible to distinguish simian malaria parasites from human malaria ones. Therefore, recorded simian malaria infections of human patients might be only a visible tip on an iceberg, and many more human infections with simian malaria might actually occur in nature.
