血液薄層塗抹標本におけるマラリア原虫感染赤血球の形態学的変化 Morphological Changes of <I>Plasmodium</I>-infected Red Blood Cells in Thin Blood Smears

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血液薄層塗抹標本におけるマラリア原虫感染赤血球の形態的変化を調べた.各症例における赤血球の平均直径は, 非感染赤血球6: 93~8.30μm, 熱帯熱マラリア原虫感染赤血球7.25~8.40μm, 三日熱7.47~10.76μm, 卵形8.64~9.36μm, 四日熱6.77~9.45μmと幅広い分布を示した: 各症例ごとに非感染赤血球の平均直径と比較した場合, 三日熱マラリア原虫環状体感染赤血球は症例の71.4%で, 栄養体, 分裂体, 生殖母体, および卵形マラリア原虫環状体, 栄養体, 生殖母体感染赤血球は全症例で有意に大きかった.また, 各原虫の発育環別では, 分裂体や生殖母体の感染している赤血球が大きい傾向がみられた.感染地域別の有意差は認められなかった.<BR>Schüffnerの斑点が認められた三日熱あるいは卵形マラリア患者の血液塗抹標本における原虫の各発育環ごとの斑点出現状況は, 三日熱マラリアでは環状体感染赤血球7.5%, 栄養体72.9%, 分裂体95.0%, 生殖母体90。0%, 卵形マラリアでは環状体感染赤血球90.0%, 栄養体95.0%, 生殖母体100.0%であった.熱帯熱マラリア患者9例の血液塗抹標本においてはMaurerの斑点はみられなかった.卵形マラリア原虫感染赤血球における鋸歯状縁の出現頻度は環状体感染赤血球20.0%, 栄養体27.5%, 生殖母体40.0%であった.多くの症例では, 適正な染色と一定数以上の感染赤血球の観察により原虫種の鑑別が可能であると考えられた.

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.<BR>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 Scht ffner'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.<BR>Mean red cell diameters of each specimen ranged as follows: 6.93.8.30μm for non-infected red cells, 7.25-8.40μm for <I>Plasmodium falciparum</I>-infected, 7.47.10.76μm for <I>P. vivax</I>-infected, 8.64-9.36μm for P. ovale-infected, and 6.77-9.45μm for P. malariae-infected ones. Red cell diameters were significantly larger in <I>P. vivax</I> (71.4% of cases for ring form, and all cases for the other developmental stages) and P. ovale (all cases for ring form, trophozoite and gametocyte)-infected ones. No significant differences in the size of infected red cells according to the area of infection were observed.<BR>The percentages of Schaffner's dots, when seen, were 7.5% ring form of <I>P. vivax</I>-infected, 72.9% trophozoite of <I>P. vivax</I>-infected, 95.0% schizont of <I>P. vivax</I>-infected, 90.0% gametocyte of <I>P. vivax</I>infected, 90.0% ring form of P. ovale-infected, 95.0% trophozoite of P. ovale-infected, and 100.0% gametocytes of P. ovale-infected red cells. The incidence of fimbriated margin on P. ovale-infected red cells by developmental stages were 20.0%, 27.5% and 40.0% for ring form-infected, trophozoite-infected, and gametocyte-infected ones. It was concluded that, in many cases, we can differentiate the species of Plasmodium by proper staining and investigation of a certain number of infected red cells.

Journal

  • Kansenshogaku Zasshi

    Kansenshogaku Zasshi 67(10), 1016-1022, 1993

    The Japanese Association for Infectious Diseases

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