A new species of simian malaria, here designated Plasmodium coatneyi, was isolated from a wild-infected Anopheles hackeri mosquito captured at Kampong Rantau Panjang near Klang in Selangor, Federation of Malaya. Its principal characteristics are as follows:
1.Young trophozoites were indistinguishable from those of P. falciparum and characterized by high frequency of double or multiple nuclei, presence of marginal forms, and other variant forms formerly associated only with P. falciparum.
2.Advanced trophozoites were usually small and round with dense and abundant cytoplasm, also resembling those of P. falciparum except that the pigment did not coalesce as maturity was reached. Maurer's spots were present and erythrocyte enlargement was not produced.
3.Schizonts were similar to those of P. falciparum except for the delay in coalescence of pigment. Merozoite number was variable but averaged about 20.
4.Gametocytes were round or oval and quite small. The pigment, usually rod-shaped, was extremely coarse and quite heavy, resembling that of P. falciparum gametocytes. Unique gametocytes with all of the heavy pigment located in a vacuole were seen.
5.The cycle in the rhesus monkey was tertian. Schizogonic forms were for the most part absent from the peripheral blood. When one brood was predominant there were alternate days of high and low parasite numbers, similar to the phenomenon sometimes seen with P. falciparum.
The suggestion was made that this species, in spite of the rounded gametocytes, may be phylogenetically related to P. falciparum, and that experimental studies of it may be useful in interpreting the cycle of P. falciparum.
Far East Research Project, Laboratory of Parasite Chemotherapy, NIAID, NIH, U. S. Public Health Service, Kuala Lumpur, Federation of Malaya.
Institute for Medical Research, Kuala Lumpur, Federation of Malaya.