Differential diagnosis of bastianellii and vivax malaria.

With a view to establishing criteria-applicable, if possible, in field work-for differentiating infection with Plasmodium bastianellii (of simian origin) from that with P. vivax (which is not infectious to rhesus monkeys), the authors describe the morphological characters of P. bastianellii as seen in simian and human blood and have followed the course of infection in these hosts.Human infections with P. bastianellii were characterized by relatively severe symptoms associated with very low parasitaemia. While no absolute criteria for differentiation between these two plasmodia have been found, the authors suggest that the presence of a scanty infection in the blood associated with small, poorly formed schizonts, which do not fill the erythrocyte, and with trophozoites of unsubstantial form is to be regarded as possibly denoting a simian origin of the infection. Subinoculation of the blood into a rhesus monkey may be the only certain guide to identification.