Biased distribution of pathogenic Entamoeba histolytica

最近，溶组织内阿米巴被认为是由一种致病性的溶组织内阿米巴和一种非致病性的溶组织内阿米巴组成。这意味着使用粪便样本显微镜检查的传统方法不能确定致病性溶组织芽孢杆菌的患病率，而从公共卫生的角度来看，这更重要。由于从囊肿中提取DNA的PCR方法已被证明可用于区分溶组织芽胞杆菌和异斑芽胞杆菌，因此将其与显微镜方法结合使用，以澄清菲律宾吕宋岛不同地区两个物种之间传播模式的差异。得到了以下结果：1)在所有调查的地方，两种寄生虫的感染率均不超过15%，而贫民区的寄生虫感染率接近70%。这表明内阿米巴的传播方式不如某些蠕虫有效。2)病原溶组织芽孢杆菌的流行率低于非病原溶组织芽孢杆菌的一半。3)两种植物的流行率各有不同。在公共卫生条件相同的情况下，较冷的气候为内阿米巴原虫的传播提供了较好的条件。4)致病性物种的分布比非致病性物种更为多样。据推测，人与人之间的传播主要通过家庭中的亲密接触来维持。因此，贫民窟地区的患病率最高。5) 5 ~ 14岁儿童患病率较高，女性患病率高于男性。这可能是由于他们的生活习惯不同造成的。6)在日本大分县高崎山的日本猴子中发现了高流行率的异棘球绦虫。这表明猴子比人类更适合作为异棘球绦虫的宿主。

Recently, Entamoeba histolytica has been recognized to consist of a pathogenic species, E. histolytica and a non-pathogenic species, E. dispar. This means that the conventional method using microscopic examination of fecal samples can not determine prevalence of pathogenic E. histolytica that is more important from the viewpoint of public health. Since the PCR method using extracted DNA from cysts has been shown to be useful for differentiation of E. histolytica from E. dispar, it was used in combination with the microscopic method to clarify the difference of the transmission mode between two species at various parts of Luzon in the Philippines. The following results were obtained.1) The prevalence of two species was not over 15% in all the places examined, although the prevalence of helminthic infection reached nearly 70% in the slum area. This indicated that the transmission mode of Entamoeba is less effective than some helminths.2) The prevalence of a pathogenic species, E. histolytica was less than a half of that of a non-pathogenic species, E. dispar in all the areas examined.3) Both species showed a with variety of prevalence according to places. If the condition of public health is similar, the colder climate provides the better condition for transmission of Entamoeba.4) The distribution of the pathogenic species was more varied than the non-pathogenic. Transmission from a human to a human is inferred to be maintained mainly by intimate contact in a family. Consequently the highest prevalence was found in the slum area.5) Higher prevalence was found in children aged from 5 to 14 years, and in women than in men. This may be caused by differences of their living habits.6) High prevalence of E. dispar was found in Japanese monkeys at the Takasaki mountain, Oita prefecture, Japan. This indicated that monkeys are more fitting hosts for E. dispar than humans.