Worm expulsion and large intestine parasitism of Strongyloides ratti as the survival strategy

一般认为，rattyloides只寄生在大鼠的小肠（SI）中，并在大约2周后被排出体外。我们报道，在蠕虫排出后，一些寄生虫在大肠（LI）中重新建立寄生，并且LI成虫产生的卵通过间接方式发育，产生自由生活的雄性和雌性。这种发育最终产生了比SI成虫更具传染性的幼虫。我们假设S. ratti可能有先天的生存策略，甚至利用宿主的防御机制。野生大鼠LI寄生现象上述假设受到质疑，因为目前还没有关于野生大鼠LI寄生的报道。我们对名古屋捕获的野生大鼠进行了检查，发现32.4%的大鼠有LI感染。LI的平均虫数仅为4.7只/只。然而，另一项实验显示，4.7只成虫每天产生4638只感染幼虫。在春季，当温度允许时，LI寄生物的数量增加，更多的是自由生长，这表明LI寄生物的生物学意义。抗氧化剂BHA对LI寄生的影响当BHA添加到实验大鼠的日常食物中时，它完全消除LI寄生而不影响SI寄生。将感染后不同天数的SI成人移植到li中，这项研究正在进行中。迄今为止获得的结果表明，无论寄生在何处，宿主免疫似乎都能减少宫内卵的数量，并增强卵在宿主外的间接发育。3 . LI寄生降低了寄生体体长和宫内卵数。电镜观察：寄生在寄主SI内的成年鼠耳曲霉肠道肿胀且充满“食物残渣”，而寄生在寄主LI内的成年鼠耳曲霉肠道受压且空。SI成虫肠细胞线粒体较多，而LI成虫肠细胞线粒体较少，但具有丰富的粗内质网。这些明显的差异似乎与蠕虫的“禁食”有关。少

It has been believed that Strongyloides ratti parasitizes only in the small intestine (SI) of rats, and expelled in ca. 2weeks. We reported that, following worm expulsion, a few parasite re-establish parasitism in the large intestine (LI), and that eggs produced by LI adults underwent the indirect way of development, producing free-living males and females. This development eventually produced far more infective larvae than SI adults. We hypothesized that S. ratti would have innate strategies to survive or even utilize host defense mechanisms.1.LI parasitism in wild ratsThe above hypothesis was questioned because no LI parasitism in wild rats has been reported. We examined wild rats captured in Nagoya, and found that 32.4% of them had infection in the LI. The average number of worms in the LI was only 4.7/rat. However, an additional experiment revealed that the 4.7 adults produced 4,638 infective larvae per day. The number of LI parasites increased in the spring, when temperature allow … More s free-living development, suggesting a biological significance of the LI parasitism.2.Effect of anti-oxidant BHA on LI parasitismWhen BHA was added to daily food for experimental rats, it abolished completely the LI parasitism without influencing the SI parasitism.3.Transplanting SI adults of different days after infection into the LIThis study is going on. The results obtained so far suggest that regardless of the site of parasitism, host immunity seemed to reduce the number of intrauterine eggs and enhance the indirect development of eggs outside a host. The LI parasitism reduced body length of parasite and the number of intrauterine eggs.4.Electron microscopical studyThe intestinal tract of adult S. ratti parasitizing in host SI was swollen and filled with "food debris", while that of adult S. ratti in the LI was compressed and empty. Intestinal cells of SI adults had many mitochondria, while those of LI adults did not, but had plenty of rough endoplasmic reticulum. These apparent difference seems to be related to ‘fasting' of worms. Less