On identification of a species of malaria parasite from monkeys.

In present paper,a species of malaria parasite from Vietnam was studied and identified.Experiments were carried out,using the rhesus monkeys as the host and with the Anophles lesteri as the vector.All asexual stages and gametoeytes were found in the peripheral circulation.The data from the infection of monkeys No.29,No.30 and No.739 indicated that an asexual cycle took 48 hours.At the third asexual cycle,maximum parasitaemia occurred in the peripheral blood.The morphological characteristics of this parasite are closely similar to those of Plasmodium vivax,which,in turn,.is similar morphologically to Plasmodium cynomolgi.The early ring form has a diameter that equals approximately to one-fourth of the diameter of an erythrocyte.Multiple invasion with two or three parasites in a corpuscle frequently occurs.With the growth of parasites Shuffner's dots appear,and a little later the corpuscle becomes slightly enlarged and pale.In trophozoites amoeboidicity is obvious and the pigments are brown in colour with a yellowish background.The mature schizont which is characterized by the division of the nuclei at dawn produces about 10 to 20 (generally 12 to 16) merozoites.Macrogametocytes and mierogametocytes appear generally by the third asexual cycle.Anopheles lesteri was tested for transmission.Monkeys No.30 and No.739 were infected experimentally by three batches of the vector with sporozoite rates of 19.0%,7.1% and 12.9 respectively.At a temperature of about 26℃ and in a relative humidity of 70 to 80%,oocysts reach maturity on day 10,and sporogony is completed in 12 days.Sporozoites in stained preparations measure 10 to 12μ in length.The pre-parasitaemia period in monkeys No.29 and No.739 was 9 and 10 days respectively after the introduction of sporozoites.Later on,Anopheles stephensi was also used as vector,and the results of the experimental infection showed that the pre-parasitaemia period was 8 to 12 days.It was,therefore,concluded that this monkey parasite is identical with Plasmo-dium cynomolgi.