The morphology of Plasmodium berghei before and after treatment with drugs

Abstract

1. (1) A description is given of normal parasites of Plasmodium berghei as seen by phase contrast microscopy, after staining with eosin, and after staining with leuco-fuchsin and methyl green. Pigment was demonstrated in trophozoites and schizonts. It was not present in the small ring stage nor in some large trophozoites developing in reticulocytes. The haemoglobin content of the parasitized erythrocytes decreased during the development of the parasites. 2. (2) Daraprim, 2 : 4-diaminopteridines and the proguanil metabolite 2 : 4-diamino-1-p-chlorophenyl-1 : 6-dihydro-6 : 6-dimethyl-1 : 3 : 5-triazine resembled proguanil and sulphadiazine in primarily attacking the early schizonts. The nuclei became finely divided and the parasites degenerated.' 3. (3) Pamaquin caused vacuolation and disintegration of the cytoplasm before the nuclei were greatly affected. 4. (4) Methylene blue also caused vacuolation and disintegration of cytoplasm. At the same time the nuclei became diffuse. 5. (5) After exposure to all the above drugs the pigment granules were larger than usual but were not extruded. 6. (6) Mepacrine and chloroquine caused rapid clumping and extrusion of pigment from trophozoites and schizonts and, less rapidly, from gametocytes. The cytoplasm then disintegrated before the nuclei appeared to be affected. 7. (7) The morphological changes caused by daraprim, 2 : 4-diaminopteridines and the proguanil metabolite have not been described before. The changes caused in P. berghei by the other drugs are similar to those previously described in other species of malaria. 8. (8) Trophozoites of P. berghei were as infective as normal for 12 hours after treatment with daraprim. Between 12 and 48 hours the degree of infectivity decreased more quickly than the percentage of morphologically normal trophozoites, although some parasites were still infective 48 hours after treatment.