The six diseases of WHO. Leishmaniasis.
The six diseases of WHO. Leishmaniasis.
复制标题
世界卫生组织的六种疾病。
DOI：
10.1136/bmj.283.6301.1245
复制
发表时间：
1981
期刊：
影响因子：
--
通讯作者：
M. Chance
中科院分区：
文献类型：
--
作者：
M. Chance
利什曼病不是一种单一疾病；相反，它是由几种不同的利什曼原虫引起的一系列疾病，每种利什曼原虫都有可能在人类身上引起一组特有的症状。对利什曼病的发病率和流行率没有可靠的估计。据估计，每年有40万新的利什曼病病例，但对公共卫生的重要性可能更好地从比哈尔邦最近内脏利什曼病流行的病例数估计来衡量，当时保守估计1977年有1.8万例，1978年有4万例（R W Ashford，个人交流）。在脊椎动物宿主中，原生动物寄生虫几乎完全局限于单核吞噬细胞（网状内皮细胞）系统的细胞，在这种系统中，它们以无纺锤体的形式存在。利什曼病的临床表现主要有皮肤和内脏两种，其分布如图1所示。在皮肤疾病中，寄生虫局限于皮肤的巨噬细胞，而在内脏疾病中，虽然在许多组织中都可以发现无毛线虫，但主要的感染中心是在肝脏、脾脏和骨髓的吞噬细胞内。对于这些不同的组织趋向性没有令人信服的解释。基于温度敏感性或代谢控制差异的论点很难与同一种寄生虫可能在一个人身上引起内脏利什曼病的观察结果相一致。但另一种是皮肤的表现图1-地理分布在皮肤和内脏感染中，该生物体都是通过昆虫媒介白蛉传播给人类的。在白蛉的消化道内，与血粉一起被摄入的无尾虫转变成纺锤形的鞭毛体——promastigote。这些是感染形式，是生命周期的阶段，可以很容易地在体外的血琼脂斜坡上生长。当一只受感染的白蛉吸食下一顿血时，前驱虫从消化道前部进入皮肤，因此新的感染开始了。多年来，利什曼病若干方面的进展由于难以在不同种类的利什曼原虫之间进行形态学区分而受到阻碍。最近的超微结构研究显示了无尾线虫在大小上的差异，但在鉴定寄生虫方面的主要进展是引入了生物化学分类学技术属的细分是复杂的，在某种程度上是有争议的。一种过于简化的分类包括多诺瓦氏杆菌，它是全世界内脏利什曼病的致病生物。在印度和东非的一些地区，这种寄生虫是人与人之间传播的，而在其他地区，狗和野生犬科动物是动物宿主。在
Leishmaniasis is not a single disease; rather, it is a collection of diseases caused by several different species of Leishmania, each of which has its own potential to cause a characteristic set of symptoms in man. No reliable estimates of the incidence and prevalence of leishmaniasis exist. It has been estimated that there are 400 000 new cases of leishmaniasis every year,' but the importance to public health is perhaps better gauged from the estimates of the number of cases in the recent epidemic of visceral leishmaniasis in Bihar, when it was conservatively estimated that there were 18 000 cases in 1977 and 40 000 in 1978 (R W Ashford, personal communication). Within the vertebrate host the protozoan parasite is restricted almost exclusively to cells of the mononuclear phagocyte (reticuloendothelial) system, in which they are present as amastigotes. Two main clinical manifestations of leishmaniasis exist-cutaneous and visceral-the distribution of which is 0 shown in fig 1. In the cutaneous disease the parasites are restricted to macrophages of the skin, whereas in the visceral manifestation, though amastigotes may be found in many tissues, the major centres of infection are within the phagocytic cells of the liver, spleen, and bone marrow. No convincing explanation of these different tissue tropisms has been presented. Arguments based on differences in temperature sensitivity or metabolic control are difficult to reconcile with the observation that the same parasite may cause visceral leishmaniasis in one individual . but a cutaneous manifestation in another.3 FIG 1-Geographical distribi In both the cutaneous and visceral infections the organism is transmitted to man by an insect vector, phlebotomine sandflies. Within the alimentary canal of the sandfly the amastigotes that are ingested together with the blood meal transform to a spindleshaped flagellated form-the promastigote. These are the infective form and are the stage of the life cycle that may be easily grown in vitro on blood-agar slopes. When an infective sandfly takes its next blood meal promastigotes are delivered from the anterior portion of the alimentary canal into the skin and thus a new infection begins. For many years progress on several aspects of leishmaniasis was handicapped by the difficulties of differentiating morphologically among the various species of Leishmania. Recent ultrastructural studies4 have shown differences in the size of amastigotes, but the main advance in identifying parasites has been the introduction of the techniques of biochemical taxonomy.56 The subdivision of the genus is complicated and to some extent controversial. An oversimplified classification includes L donovani, the causative organism of visceral leishmaniasis throughout the world. In India and some parts of East Africa transmission of this parasite is from man to man, while in other areas dogs and wild canids act as an animal reservoir. In the