Symposium on Exoerythrocytic Forms of Malarial Parasites. IV. The Chemotherapy and Immunology of Pre-Erythrocytic Stages in Avian Malaria

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Abstract
The action of various anti-malarial drugs on the pre-erythrocytic stages of Plasmodium gallinaceum was studied cytologically. Cryptozoites were able to grow in the macrophages of the skin in chickens fed sulfadiazine, sulfamerazine, sulfapyrazine, a metanilamide and a naphthoquinone in dosages several times as great as was necessary to prevent parasitemia. The majority of such cryptozoites were normal in appearance. However, sulfadiazine, the naphthoquinone and to a lesser extent, tne metanilamide produced marked damage to some of them. The effects of the above-mentioned prophylactic drugs on metacryptozoites were more marked. The suppressive drugs quinine, quina-crine, chloroquine, pamaquine, and pentaquine produced morphological changes in both cryptozoites and metacryptozoites but no appreciable reduction in the numbers of merozo-ites. Comparisons between the type of cytological effects produced by chemotherapeutic agents and the natural and acquired immunity of the hosts indicated that these were essentially similar.