Skov Jakob, Kania Per W, Dalsgaard Anders, Jørgensen Thomas R, Buchmann Kurt
Department of Veterinary Pathobiology, Faculty of Life Sciences, University of Copenhagen, Frederiksberg C, Denmark.
Vet Parasitol. 2009 Mar 9;160(1-2):66-75. doi: 10.1016/j.vetpar.2008.10.088. Epub 2008 Oct 28.
A survey of digenean zoonotic trematodes infecting snails and fishes in a North Vietnamese freshwater fish culture system revealed shedding of three types of parapleurolophocercous cercariae from the snail host Melanoides tuberculata and the presence of metacercariae within the genus Haplorchis (H. pumilio and H. taichui) and Procerovum sp. in tissues of cultured fishes (silver carp, Indian carp and climbing perch). No morphological characters were able to link the different cercariae specifically to any of the metacercariae. Subsequent molecular work including PCR and sequencing of ribosomal DNA (the ITS2 region) in cercariae and metacercariae associated only one type of the cercariae to the recovered H. pumilio metacercariae. Further, full identity (100%) was found with regard to the ITS sequence of adult H. pumilio obtained from the same North Vietnamese region. None of the cercariae showed sequence identities with H. taichui but more than 99% identity was found between one cercaria type and the Procerovum sp. metacercaria. It was indicated that trematode parasites of farmed fishes may originate from sources outside the fish ponds and may be introduced as free-swimming cercariae when pond water is being replenished by river water. Likewise, cercariae from the ponds may not always result in metacercarial infections of the farmed fishes. The present study frames the needs for including molecular techniques as auxiliary tools when conducting ecological studies of cercariae in complex ecosystems. The parasites recorded in the fish ponds are not only known to affect the health of aquacultured fishes but also the documented zoonotic potential of the diagnosed metacercaria calls for alerts regarding human consumption of raw or inadequately processed fish dishes.
对越南北方淡水鱼养殖系统中感染蜗牛和鱼类的复殖目人畜共患吸虫进行的一项调查显示，在蜗牛宿主瘤拟黑螺中排出了三种侧叶尾蚴，并在养殖鱼类（鲢鱼、印度鲤和攀鲈）的组织中发现了哈氏属（矮小哈氏吸虫和Tai氏哈氏吸虫）和原角属吸虫的囊蚴。没有形态特征能够将不同的尾蚴与任何一种囊蚴明确联系起来。随后的分子研究，包括对尾蚴和囊蚴的核糖体DNA（ITS2区域）进行PCR和测序，仅将一种尾蚴与回收的矮小哈氏吸虫囊蚴联系起来。此外，从同一越南北方地区获得的成年矮小哈氏吸虫的ITS序列完全相同（100%）。没有尾蚴与Tai氏哈氏吸虫显示出序列同一性，但在一种尾蚴类型和原角属吸虫囊蚴之间发现了超过99%的同一性。结果表明，养殖鱼类的吸虫寄生虫可能源自鱼塘之外的来源，并且当河水补充池塘水时，可能以自由游动的尾蚴形式引入。同样，来自池塘的尾蚴不一定总能导致养殖鱼类的囊蚴感染。本研究提出了在复杂生态系统中对尾蚴进行生态研究时，需要将分子技术作为辅助工具。鱼塘中记录的寄生虫不仅已知会影响养殖鱼类的健康，而且已诊断出的囊蚴的人畜共患潜力也要求对人类食用生的或加工不当的鱼菜肴发出警报。
