Susceptibility of Guyanan Saimiri monkeys to a chloroquine-sensitive and a chloroquine-resistant strain of Plasmodium vivax from Papua New Guinea.

Attempts were made to infect splenectomized Guyanan Saimiri sciureus monkeys with the following Papua New Guinean strains of Plasmodium vivax: AMRU-1, a chloroquine-resistant strain; and AMRU-2, a chloroquine-sensitive strain. Inoculation of 7 monkeys with the AMRU-1 strain, 4 using blood-stage parasites and 3 using sporozoites, all failed to produce infections. Inoculation of 4 monkeys with the AMRU-2 strain, 3 using blood-stage parasites and 1 using sporozoites, were all successful in establishing infections. The results suggest that Guyanan Saimiri are refractory to infection with the AMRU-1 strain. If refractoriness occurs in other species and subspecies of Saimiri monkeys, then studies on the AMRU-1 strain of P. vivax may be restricted to work using Aotus monkeys.