Studies on Human Malaria in Aotus Monkeys, IV. Development of Plasmodium falciparum in Two Subspecies of Aotus trivirgatus

Abstract

Comparative susceptibility studies with a strain of Plasmodium falciparum from Panama indicated that the Aotus trivirgatus griseimembra subspecies of douroucoulis monkeys is more susceptible to infection than is the A. t. trivirgatus subspecies. Serum electrophoretic studies indicated that all of the latter contained a third alpha globulin whereas the former contained only 2. Preinoculation serum electrophoretic studies may be useful as indicators of the level of susceptibility of these animals to this parasite. As reported previously (Collins et al., 1973), a strain of Plasmodium falciparum from Panama (Panama II) has been established in Aotus trivirgatus monkeys. Previous observations had indicated, however, that differences exist in the susceptibility of these monkeys to infection, particularly in the orange-throated variety. All of our previous studies with this strain had been with the grey-legged douroucoulis, A. trivirgatus griseimembra. The availability of a number of the orange-throated animals, identified as A. t. trivirgatus, the three-lined douroucoulis, at the same time made possible a comparison of the susceptibility of these two subspecies to the Panama II strain, the results of which are reported here. MATERIALS AND METHODS The monkeys were procured primarily from Tarpon Zoo, Tarpon Springs, Florida, which imported the animals directly from Colombia, South America. Prior parasitologic and serologic examination indicated that the animals were free of natural malarial infection. Some of the animals were splenectomized prior to infection according to the technique of Sodeman et al. (1970). All but 2 of the A. t. trivirgatus monkeys (AO-419 and AO-426) were infected with microfilariae which were usually abundant on the routine blood films. All animals were infected by the intravenous inoculation of parasitized heparinized blood via the femoral vein. Thick and thin blood films (Earle-Perez) were stained with Giemsa stain and the parasite counts recorded per mm3. During the early and late stages of the infections, blood films were made 3 times a week; during other periods, blood films were made daily. Total proteins in the serum samples were deReceived for publication 15 November 1973. termined by the routine biuret method (Weichselbaum, 1946) and read on a Beckman? DU spectrophotometer at 540 mAu. Serum protein electrophoretic studies were conducted using a Beckman? Model R-100 Microzone? electrophoresis system utilizing cellulose acetate membranes. Membranes were scanned in an R-110 Microzone? densitometer using a 520-m,t interference filter.