Mak J W
International Medical University, Sesama Centre, Plaza Komanwel, Bukit Jalil, 57000 Kuala Lumpur, Malaysia.
Trop Biomed. 2004 Dec;21(2):39-50.
Intestinal protozoa are increasingly being studied because of their association with acute and chronic diarrhoea in immunocompromised as well as immunocompetent patients. Various community outbreaks due to contamination of water or food with these protozoa have further highlighted their importance in public health. Among these important pathogens are Giardia duodenalis, Entamoeba histolytica, Cryptosporidium parvum, Cyclospora cayetanensis, Isospora belli, and microsporidia. Except for the cyst-forming G. duodenalis and E. histolytica, the others are intracellular and form spores which are passed out with the faeces. These organisms are also found in various animals and birds and zoonotic transmission is thought to occur. These infections are distributed worldwide, with a higher prevalence in developing compared to developed countries. However, the relative importance of zoonotic infections especially in developing countries has not been studied in detail. The prevalence rates are generally higher in immunodeficient compared to immunocompetent patients. Higher prevalence rates are also seen in rural compared to urban communities. Most studies on prevalence have been carried out in developed countries where the laboratory and other health infrastructure are more accessible than those in developing countries. This relative inadequacy of laboratory diagnosis can affect accurate estimates of the prevalence of these infections in developing countries. However, reports of these infections in travellers and workers returning from developing countries can provide some indication of the extent of these problems. Most studies on prevalence of amoebiasis in developing countries were based on morphological identification of the parasite in faecal smears. As the pathogenic E. histolytica is morphologically indistinguishable from that of non-pathogenic E. dispar, estimates of amoebiasis may not be accurate. The epidemiology of human microsporidia infections is not completely understood. Two species, Enterocytozoon bieneusi and Encephalitozoon intestinalis, are associated with gastrointestinal disease in humans and it is believed that human to human as well as animal to human infections occur. However, the importance of zoonotic infections has not been fully characterised. G. duodenalis cysts, microsporidia and Cryptosporidium oocysts have been detected in various ground water resources, but their role in community outbreaks and maintenance of the infection has not been fully characterised. The taxonomic classification and pathogenic potential of B. hominis are still controversial. While considered by many as yeast, fungi or protozoon, recent sequence analysis of the complete SSUrRNA gene has placed it within an informal group, the stramenopiles. This review covers recent published data on these zoonotic infections and examines their public health importance in Asian countries.
由于肠道原生动物与免疫功能低下及免疫功能正常患者的急慢性腹泻有关，因此对其研究日益增多。这些原生动物污染水或食物导致的各种社区疫情，进一步凸显了它们在公共卫生中的重要性。这些重要病原体包括十二指肠贾第虫、溶组织内阿米巴、微小隐孢子虫、卡耶塔环孢子球虫、贝氏等孢球虫和微孢子虫。除了形成包囊的十二指肠贾第虫和溶组织内阿米巴外，其他都是细胞内寄生虫，并形成孢子随粪便排出。这些生物体在各种动物和鸟类中也有发现，并且认为存在人畜共患病传播。这些感染在全球范围内都有分布，与发达国家相比，发展中国家的患病率更高。然而，人畜共患病感染的相对重要性，尤其是在发展中国家，尚未得到详细研究。与免疫功能正常的患者相比，免疫缺陷患者中的患病率通常更高。与城市社区相比，农村地区的患病率也更高。大多数关于患病率的研究是在发达国家进行的，那里的实验室和其他卫生基础设施比发展中国家更容易获得。实验室诊断的这种相对不足，可能会影响对发展中国家这些感染患病率的准确估计。然而，从发展中国家返回的旅行者和工人中这些感染的报告，可以提供一些关于这些问题严重程度的线索。发展中国家大多数关于阿米巴病患病率的研究，是基于粪便涂片中原虫的形态学鉴定。由于致病性溶组织内阿米巴在形态上与非致病性迪斯帕内阿米巴无法区分，阿米巴病的估计可能不准确。人类微孢子虫感染的流行病学尚未完全了解。两种微孢子虫，即比氏肠微孢子虫和肠道脑炎微孢子虫，与人类胃肠道疾病有关，并且认为存在人传人以及动物传人感染。然而，人畜共患病感染的重要性尚未得到充分认识。在各种地下水资源中检测到了十二指肠贾第虫包囊、微孢子虫和隐孢子虫卵囊，但它们在社区疫情和感染维持中的作用尚未得到充分认识。人芽囊原虫的分类和致病潜力仍存在争议。虽然许多人认为它是酵母、真菌或原生动物，但最近对完整的小亚基核糖体RNA基因的序列分析将其归入一个非正式的类群——不等鞭毛类。本综述涵盖了关于这些人畜共患病感染的最新发表数据，并探讨了它们在亚洲国家的公共卫生重要性。
