[Morphological changes of Plasmodium-infected red blood cells in thin blood smears]

Malaria is absent in Japan, but about sixty imported cases are reported in a year. We think it desirable that all medical care institutions should examine for malaria infection promptly. Diagnosis of malaria, in Japan, depends mostly on the examination of thin blood smears stained by Giemsa. However, we sometimes find atypical changes of infected red blood cells, especially in their size. It was also presumed that infected red cells may differ in their size and other morphology by their geographical origin. The present study was designed to investigate the influences of malaria infection on the morphology of host red cells. Thin blood smear samples from the cases of a single species plasmodial infection with epidemiological circumstances were chosen for this investigation from the specimens which we examined in our laboratory. Cases with a history of chemoprophylactic or chemotherapeutic use within 1 month prior to the blood examination were excluded. Cases were classified according to species of the infected parasites and the geographical origin; Africa, South-East Asia, and Western Pacific. The distribution of red cell diameters and the ratio of maximum diameter to minimum diameter were determined on blood smears using oil immersion lens. Measurement was completed with 20 or 30 infected red cells for each developmental stage of the parasites and 30 non-infected red cells per slide. The presence of Schüffner's dots was observed on blood smears from vivax or ovale malaria patients. We examined also for Maurer's dots and fimbriated margin of red cells on falciparum and ovale malaria specimens respectively.(ABSTRACT TRUNCATED AT 250 WORDS)