Observations on the Pre-erythrocytic Stages of Plasmodium Relictum, Plasmodium Cathemerium, and Plasmodium Gallinaceum in Various Birds

Abstract

Search for pre-erythrocytic and erythrocytic stages of the above 3 spp. of parasites was made in 15 new parasite-host combinations. Neither was found in: P. relictum in chickens or guinea-fowl; P. cathemerium in ring-neck doves; P. gallinaceum in guinea-fowl, California Valley quail or ring-neck doves. Pre-erythrocytic but no erythrocytic stages were found of P. relictum in turkeys, pheasants and ducks; of P. cathemerium in ducks; and of P. gallinaceum in turkeys and canaries. Both stages were found in canaries inoculated with sporozoites of P. cathemerium and in pheasants inoculated with sporozoites of P. gallinaceum. Erythrocytic but no pre-erythrocytic stages of P. gallinaceum were found in pigeons. No clear relationship was discovered between ability of sporozoites to develop in the tissues of hosts and the systematic classification of the hosts. Degenerating pre-erythrocytic stages were observed along with normal ones in the tissues of ducks inoculated with sporozoites of eithex P. relictum or P. gallinaceum. Degenerative changes in the pre-erythrocytic stages of P. gallinaceum in chickens with acquired immunity were similar to changes observed in corresponding stages effected by natural immunity or by anti-malarial drugs. Pre-erythrocytic stages of P. cathemerium were morphologically similar to, but not identical with, those of P. relictum. Cryptozoites of P. gallinaceum were found only in the spleen of chicks which received 100-300 sporozoites intraven.; metacryptozoites were found in all organs except bone marrow. The observed morph. similarities between exoerythrocytic stages of P. gallinaceum and of Leucocytozoon indicate a possibly closer systematic relationship between Plasmodium and Leucocytozoon than formerly believed.