Plasmodium simium in the Aotus trivirgatus Monkey

Abstract

Plasmodium simium was shown to be infectious to Aotus trivirgatus monkeys by the inoculation of sporozoites or parasitized blood. Anopheles freeborni mosquitoes were infected by feeding on an intact monkey. However, splenectomy resulted in increased parasitemia and increased mosquito infection leveis. Since the discovery that the owl monkey, Aotus trivirgatus, was susceptible to infection with the human malarias (Young et al., 1966), there has been a great interest in investigating these animals as hosts for the human and nonhuman malarias. Of the two species of nonhuman primate malarias which have been reported from South America, Plasmodium simium and P. brasilianum, only the latter has been shown to be transmissible to Aotus monkeys by sporozoite inoculation (Coatney et al., 1971). However, daily feeding of mosquitoes on infections of P. brasilianum in Aotus failed to result in infection. It appears, therefore, that the infection in this host may be a dead end. Reported here are the results of studies to determine if the Aotus monkey is susceptible to P. simium and, once infected, to determine if it could serve as a host for mosquito infection. MATERIALS AND METHODS The strain of P. simium was provided by Dr. L. M. Deane in blood from a natural infection in the howler monkey (No. 397) and was received for study in our laboratory in 1966 where this strain has been maintained in the squirrel monkey, Saimiri sciureus (Collins et al., 1969). The A. freeborni mosquitoes were the F-1 strain originally isolated from Marysville, California, and maintained for many years in our laboratory (Hardman, 1947). The procedures used for feeding the mosquitoes on the monkeys were reported earlier (Collins et al., 1968). Aotus trivirgatus monkeys were obtained commercially. Prior serologic and parasitologic examination indicated that they were free of natural malaria infection. During the infection, thick (Earle-Perez) and thin blood films were made and stained with Giemsa stain. Parasite counts were recorded per Received for publication 3 August 1972. mm3 and gametocyte counts were recorded per 100 WBC. The splenectomy of monkey AO-281 was performed using the technique of Sodeman et al. (1970).