Actual transmission modes of pathogenic Entamoeba histolytica and Cryptosporidium

最近，利用新的基因技术建立了溶组织内阿米巴和隐孢子虫的新分类。这促使我们重新检查两种寄生虫真正致病物种的传播方式。我们对菲律宾和尼泊尔的两个物种进行了流行病学调查，这些物种是此类感染的常见地。所得结果为1。结果：1.病原菌(溶组织内阿米巴)与非致病种(埃迪帕尔)共存，但不同地区包囊携带者中E.H.的比例不同，从10%到30%不等。在人口稠密的房屋条件下，囊虫携带者的患病率很高，这表明人与人之间的直接接触是传播的第一危险因素。无症状包囊携带者高发于青年一代(5~20岁)，而严重症状性感染(肝脓肿)仅见于成年男性(20~60岁)。年轻人群中E.H.的血清阳性例数也最高，说明E.H.感染普遍较短。从血清阳性模式来看，隐孢子虫的感染模式似乎与E.A.相似。未发现隐孢子虫无症状卵囊携带者。蛔虫和蓝氏贾第鞭毛虫的感染模式似乎与E.H.和隐孢子虫不同，我们的结果表明，改善供水系统和厕所等顺序控制措施可能会导致感染。对减少E.H.和隐孢子虫效果不佳。

Recently, new taxonomic classification of Entamoeba histolytica and Cryptosporidium have been established using new genetic technology. This drove us to reexamine the transmission mode of really pathogenic species of two parasites. We conducted epidemiological surveys of two species in the Philippines and Nepal where these infections are commonly seen. Obtained results are1. Pathogenic species ( Entamoeba histolytica ) and non-pahtogenic species ( Edispar) coexisted in all the area examined, but the proportion of E. h. in all cyst carriers was varied from 10 % to 30 % in different localities.2. High prevalence of cyst-carriers was seen in a densely populated house condition, indicating direct contact between persons is the first risk-factor for transmission.3. The peak ofasymptomatic cyst-carriers of E. h. and E. d was seen in young generation ( 5-20 years ) of both sexes, whereas severe symptomatic infections ( liver abscess ) were exclusively found in male adults ( 20-60 years ).4. Seropositive cases to E. h. were also highest in young population, indicating E. h. infections are commonly short.5. The mode of Cryptosporidium infection seems to be similar to E. A, judging from the sero-positive pattern.6. Asymptomatic oocyst-carriers of Cryptosporidium were not found.7. The mode of infection ofAscaris lumbricoides and Giardia lamblia seems to be different from that of E. h. and Cryptosporidium.Our results indicated that ordinal control methods such as improvement of the water-supply system and toilets may. not be effective for reduction of E. h. and Cryptosporidium.