The Development of Plasmodium Gallinaceum from Sporozoite to Erythrocytic Trophozoite

Abstract

A technic developed for the study of the early development of malarial parasites in the vertebrate host was used. Sporozoites of P. gallinaceum entered cells of the lymphoid-macrophage system within 30 mins. after inoculation into the skin of chickens. These cells served as hosts for all stages of the 1st generation of parasites (cryptozoites) from forms still recognizable as sporozoites to large schizonts and segmenters. Sporo-zoites were found in heterophil leucocytes as late as 6 hrs. following inoculation, but only a few of these showed any appreciable development after 24 hrs., and none was found to complete its development in this type of cell. Sporozoites were not found in the intercellular spaces after 6 hrs. The first, or cryptozoic, generation required about 42 hrs. (36-48) whether the parasites grew locally at the site of inoculation or in the spleen. The 2d generation of parasites (metacryp-tozoites) was found in cells of the lymphoid-macrophage system and in endothelial cells. This generation underwent segmentation at 70-84 hrs. The first erythrocytic parasite was found 75 hrs. after intraven. inoc. of sporozoites. After 60 hrs., numerous metacryptozoites were observed, especially at the site of intradermal inoculation and in the spleen, heart, kidney and brain, after intraven. inoculation of sporozoites. At the same time, sparse erythrocytic parasites were seen at 90 hrs., after which they gradually increased in numbers up to about 6 days. Then followed a precipitous increase in erythrocytic parasites. Five days after inoculation of sporozoites or the bites of mosquitoes, 2 types of segmenters were abundant:[long dash]smaller numbers of large-sized merozoites of the cryptozoic type (macromero-zoites); and large numbers of smaller-sized, tightly packed merozoites of the type seen in blood-induced infections (micromerozoites.).