Doanh P N, Thaenkham U, An P T, Hien H V, Horii Y, Nawa Y
Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology,Hanoi,Viet Nam.
Department of Helminthology,Faculty of Tropical Medicine, Mahidol University,Bangkok,Thailand.
J Helminthol. 2015 Mar;89(2):182-8. doi: 10.1017/S0022149X13000734. Epub 2013 Nov 14.
Paragonimus heterotremus, which is an important pathogen for human paragonimiasis in Asia, is recognized as having the smallest metacercariae (maximum diameter < 300 μm) of any previously reported Paragonimus species. Recently, P. pseudoheterotremus has been described from Thailand as a new species having metacercariae (about 200 μm) slightly smaller than those of Thai P. heterotremus. In fact, the small size of P. pseudoheterotremus metacercariae is compatible with those of P. heterotremus from India and China. In this study in Vietnam, we found variably sized small metacercariae which are expected to consist of both P. heterotremus and P. pseudoheterotremus. Contrary to expectation, the adult flukes obtained by separate infection of experimental cats with different sized metacercariae were all identified as P. heterotremus, using both morphological and molecular characteristics. The molecular analyses of an extensive collection of P. heterotremus/P. pseudoheterotremus isolates from Asian countries also indicated that genetic distances between different populations of P. heterotremus are even larger than that between P. pseudoheterotremus and P. heterotremus. The haplotype network showed that all P. heterotremus and P. pseudoheterotremus isolates formed a P. heterotremus complex consisting of three groups with strong geographical origins. In addition, the Indian P. heterotremus group is the root of the other P. heterotremus and P. pseudoheterotremus populations. Based on the observed metacercarial polymorphisms and genetic variation in P. heterotremus, P. pseudoheterotremus should be considered a geographically isolated population of the P. heterotremus complex.
异盘并殖吸虫是亚洲人体并殖吸虫病的重要病原体，被认为是所有此前报道的并殖吸虫物种中尾蚴最小的（最大直径<300μm）。最近，泰国报道了拟异盘并殖吸虫这一新物种，其尾蚴（约200μm）比泰国的异盘并殖吸虫略小。事实上，拟异盘并殖吸虫尾蚴的小尺寸与来自印度和中国的异盘并殖吸虫的尾蚴尺寸相符。在越南的这项研究中，我们发现了大小不一的小型尾蚴，预计它们由异盘并殖吸虫和拟异盘并殖吸虫组成。与预期相反，用不同大小的尾蚴分别感染实验猫所获得的成虫，利用形态学和分子特征均被鉴定为异盘并殖吸虫。对来自亚洲国家的大量异盘并殖吸虫/拟异盘并殖吸虫分离株进行的分子分析还表明，异盘并殖吸虫不同种群之间的遗传距离甚至大于拟异盘并殖吸虫与异盘并殖吸虫之间的遗传距离。单倍型网络显示，所有异盘并殖吸虫和拟异盘并殖吸虫分离株形成了一个由具有强烈地理起源的三个组组成的异盘并殖吸虫复合体。此外，印度异盘并殖吸虫组是其他异盘并殖吸虫和拟异盘并殖吸虫种群的根源。基于观察到的异盘并殖吸虫尾蚴多态性和遗传变异，拟异盘并殖吸虫应被视为异盘并殖吸虫复合体的一个地理隔离种群。
