Actual transmission modes of pathogenic Entamoeba histolytica and Cryptosporidium

近年来，利用新的遗传技术建立了溶组织内阿米巴和隐孢子虫的新分类。这促使我们重新审视两种真正致病的寄生虫的传播模式。我们在菲律宾和尼泊尔对两种常见感染的物种进行了流行病学调查。得到的结果如下：1。病原菌种（溶组织内阿米巴）和非致病性菌种（Edispar）在所有检查区域共存，但不同地区大肠杆菌在所有囊肿携带者中的比例从10%到30%不等。在人口密集的房屋条件下，可见囊肿携带者的高流行率，表明人与人之间的直接接触是传播的首要危险因素。无症状性e.h.和e.d.s囊肿携带者的高峰出现在男女的年轻一代（5-20岁），而严重症状性感染（肝脓肿）只出现在男性成年人（20-60岁）中。年轻人感染大肠杆菌的血清学阳性病例也最多，这表明大肠杆菌感染的时间通常较短。从血清阳性模式判断，隐孢子虫感染的模式似乎与e.a相似。未发现隐孢子虫无症状卵囊携带者。类蚓蛔虫和贾第鞭毛虫的感染方式似乎与大肠杆菌和隐孢子虫的感染方式不同。我们的研究结果表明，改善供水系统和厕所等有序的控制方法可能会导致污染。对减少大肠杆菌和隐孢子虫没有效果。

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.