Presbytis entellus, a new experimental host for Plasmodium fragile.

The course of blood-induced Plasmodium fragile infection in 3 simian hosts, Macaca radiata (bonnet monkey), Macaca mulatta (rhesus monkey), and Presbytis entellus (Indian langur), was studied. The infection in 8 bonnet monkeys was very mild and nonfatal. In M. mulatta, P. fragile produced acute initial infection followed by anemia and death in 3 of 6 monkeys. The parasite has a relatively high level of virulence for P. entellus, a new experimental host for P. fragile, in which peak parasitemia ranging between 15 and 75% was recorded, and the infection was uniformly fatal. Plasmodium fragile infection in P. entellus can serve as an ideal biological counterpart to human Plasmodium falciparum.