Adaptation of the Panama II strain of Plasmodium falciparum to Panamanian owl monkeys.

The Panama II strain of Plasmodium falciparum, acquired at the second passage level in splenectomized Colombian owl monkeys, was adapted to owl monkeys of Panamanian origin. Patent infections were induced in 22 of 27 unaltered and 20 of 21 splenectomized recipients during 19 serial passages. The infections were significantly more virulent in splenectomized than normal Panamanian owl monkeys, however recrudescences in seven normal monkeys achieved peak parasitemias 48 times greater than in the primary attack. These results describe the first reproducible infections of indigenous falciparum malaria in Panamanian owl monkeys.

Studies with induced malarias in Aotus monkeys.

Aotus monkeys have been shown to be susceptible to the three most important species of human malaria as well as to simian, ape, and rodent malaria. The parasites natural to man were maintained by serial passages using trophozoite infected blood. It was then possible to transfer the infections to, and among, other New World monkeys which previously were refractory. The parasites retained their viability in the monkey, were infective to mosquitos, and were transmitted between monkeys and back to man. Exoerythrocytic stages, similar to those demonstrated in man, occurred in the Aotus liver. Drugs exerted similar action against the parasites in the monkey as against parasites in man. The human malaria-Aotus model has made possible other extensive studies in various disciplines important to the understanding of the parasites in man. These included parasite biology, host-parasite-vector relationships, immunology, pathology, and physiology.

Chemotherapy of Plasmodium vivax in Saimiri and Aotus models.

Three standard antimalarial compounds were tested against trophozoite or sporozoite induced infections of the Panamanian Achiote strain of Plasmodium vivax in two species of monkeys. In Saimiri sciureus (24 subjects) and Aotus trivirgatus (11 subjects), parasite clearance from the peripheral blood averaged 3 days after initiating chloroquine therapy (total dose of 25 mg base/kg body weight over 3 days or single dose of 10 mg base/kg. Trophozoite induced infections were cured in all of 10 Saimiri and all of 6 Aotus, as indicated by the absence of relapses. Relapses did occur in 3 of 11 tests with Saimiri and 3 of 5 tests with Aotus against sporozoite induced infections. Subpatent periods ranged from 38 to 111 days among intact and splenectomized hosts. This is the first chemotherapeutic evidence for the persistence of exoerythrocytic stages of P. vivax in New World monkeys. Pyrimethaminr (single dose of 1 mg/kg) cured trophozoite induced infections in all of five Saimiri hosts. Radical cure of sporozoite induced infections was accomplished in each of six trials with chloroquine (25 mg base/kg) plus primaquine (1 mg base/kg for 14 days). The primary attack or relapse was treated. These models warrant further investigation in chemotherapy.

The prevalence of trypanosomes and microfilariae in Panamanian monkeys.

A total of 3,523 wild caught monkeys from Panama was examined for blood parasites from August 1968 through June 1972. Trypanosomes or microfilariae were observed in the blood of 31.1% of the monkeys. Mixed infections, with microfilariae and trypanosomes, were detected in 6.6% of the animals. Trypanosoma cruzi was found in marmosets. Saguinus geoffroyi (12.2%), in white-faced capuchins, Cebus capucinus (5.0%), in squirrel monkeys, Saimiri sciureus (1.7%) and in black spider monkeys, Ateles fusciceps (1.2%). Trypanosoma rangeli was found in S. geoffroyi (55.8%) and C. capucinus (12.5%). Other trypanosomes found in Panamanian monkeys included T. minasense, and T. mycetae. Saguinus geoffroyi showed the highest infection rate (88.9%) with trypanosomes and/or microfilariae; trypanosomes were seen in 68.1%, and microfilariae in 73.0%, of the animals examined. The marmosets, white-faced capuchins, and squirrel monkeys should be considered as significant hosts of T. cruzi in sylvatic habitats and may serve as reservoir hosts of Chagas' disease in Panama. The microfilariae seen in monkeys from Panama were tentatively identified as larval forms of Dipetalonema gracile in Aotus trivirgatus; D. obtusa in C. capucinus and S. geoffroyi; and D. marmosetae in Alowatta villosa, C. capucinus, A. trivirgatus, S. sciureus, A. fusciceps, and S. geoffroyi.