Moazeni Mohammad, Ahmadi Amin
Department of Pathobiology, School of Veterinary Medicine, Shiraz University, Shiraz, Iran.
Department of Pathobiology, School of Veterinary Medicine, Shiraz University, Shiraz, Iran.
Exp Parasitol. 2016 Oct;169:81-9. doi: 10.1016/j.exppara.2016.07.010. Epub 2016 Jul 28.
Fasciola hepatica is a well-known helminth parasite, with significant economic and public health importance all over the world. It has been known since more than 630 years ago and a considerable research work has been carried out on the life cycle of this important parasite. In the hepatic phase of the life cycle of F. hepatica, it is assumed that the young flukes, after about 6-7 weeks of migration in the liver parenchyma, enter into the bile ducts of the definitive hosts and become sexually mature. Even though the secretion of cysteine peptidases including cathepsin L and B proteases by F. hepatica may justify this opinion, because of several scientific reasons and based on the experimental studies conducted in different animals (reviewed in this article), the entry of parasites into the bile ducts, after their migration in the liver parenchyma seems to be doubtful. However, considering all the facts relating to the hepatic and biliary phases of the life cycle of F. hepatica, two alternative ideas are suggested: 1) some of the migrating juvenile flukes may enter into the bile ducts immediately after reaching the liver parenchyma while they are still very small, or 2) when newly excysted juvenile flukes are penetrating into the intestinal wall to reach the liver through the abdominal cavity, a number of these flukes may enter into the choleduct and reach the hepatic bile ducts, where they mature. According to the previously performed natural and experimental studies in different animals and human beings, the supporting and opposing evidences for the current opinion as well as the evidences that might justify the two new ideas are reviewed and discussed briefly. In conclusion, our present knowledge about the time and quality of the entry of F. hepaticas into the bile ducts, seems to be insufficient, therefore, there are still some dark corners and unknown aspects in this field that should be clarified.
肝片吸虫是一种广为人知的蠕虫寄生虫，在全球具有重大的经济和公共卫生意义。它早在630多年前就已为人所知，并且针对这种重要寄生虫的生命周期开展了大量研究工作。在肝片吸虫生命周期的肝脏阶段，一般认为，幼吸虫在肝实质中移行约6 - 7周后，进入终末宿主的胆管并性成熟。尽管肝片吸虫分泌包括组织蛋白酶L和B蛋白酶在内的半胱氨酸肽酶或许可以支持这一观点，但出于一些科学原因，并基于在不同动物身上进行的实验研究（本文对此进行了综述），寄生虫在肝实质中移行后进入胆管这一说法似乎存在疑问。然而，综合考虑与肝片吸虫生命周期中肝脏和胆管阶段相关的所有事实，提出了两种替代观点：1）一些移行的幼吸虫在刚到达肝实质且仍非常小时，可能立即进入胆管；或者2）新脱囊的幼吸虫在穿透肠壁经腹腔到达肝脏时，其中一些吸虫可能进入胆总管并到达肝内胆管，在那里成熟。根据先前在不同动物和人类身上进行的自然和实验研究，对当前观点的支持和反对证据以及可能支持这两种新观点的证据进行了简要回顾和讨论。总之，我们目前关于肝片吸虫进入胆管的时间和情况的了解似乎并不充分，因此，该领域仍存在一些有待阐明的未知角落和方面。
