Investigation And Analysis On The Infection Of Major Freshwater Fish

Heilongjiang is rich in freshwater fish resources, totalling over90species, and most of themcan serve as the second intermediate host of digenetic trematode. These trematode can severelyimpact the development of animal husbandry and human health and some of these worms areharmful, including Clonorchis sinensis, Metorchis orientalis, Echinostoma hortense and so on.Animal and human infections are caused by eating raw or undercooked fish containingmetacercariae. Therefore, the present study was to investigate the fishborne trematodemetacercariae infection in freshwater fishes in different river basins in Heilongjiang Province,China, which would provide “base-line” data for assess the risk for human infection and forexecute comprehensive control programs.To understand the prevalence of fishborne trematode infection in commom freshwater fishes,some samples of freshwater fishes from Songhua river, Nenjiang river, Mudanjiang river andother lakes or ponds in representative cities in Heilongjiang Province were investigated betweenSeptember2011and December2014. They were individually separated by direct compressionand artificial digestion technique, and then were identified by themodern molecular biology methods and animal experimental infection. According to the survey,recommended preventive and control measures were made.Thirteen species of freshwater fish (n=6791) were collected, including Pseudorasboraparva(1626), Hemicculter Leuciclus(529), Saurogobio dabryi(1129), Phoxinus lagowskii(752),Carassius auratus(832), Rhodeus ocellatus(393), Perccottus glehnii (430), Misgurnusanguillicaudatus (461), Xenocypris davidi(146), Cyprinus carpio(85), Pelteobagrus fulvidraco (175), Hemibarbus maculatus (153). Six types of metacercariae of freshwater fish were detectedin this survey, and the metacercariae were Clonorchis sinensis, Metorchis orientalis, Metorchistaiwanensis, Echinostoma hortense, Metagonimus yokogawai, and Exorchis sp. The overallprevalence of fishborne trematode metacercariae infection in6791examined freshwater fisheswas18.80%(1277/6791), the average prevalences of fishborne trematode metacercariaeinfection in Songhua river, Nenjiang river, Mudanjiang river and lakes or ponds were32.31%(852/2637),10.08%(195/1935),15.38%(44/286) and9.62%(186/1933), respectively. Theprevalence of fishborne trematode in freshwater fishes in Songhuajiang river was significantlydifference with Nenjiang river and rivers or ponds (P＜0.05), so did the Mundangjiang riverwith Nenjiang river and rivers or ponds(P＜0.05). Others were all not significantly difference(P＞0.05). The average prevalences of fishborne trematode metacercariae infection inClonorchis sinensis, Metorchis orientalis, Metorchis taiwanensis, Echinostoma hortense,Metagonimus yokogawai, and Exorchis sp. were15.55%,10.59%,2.31%,1.65%,0.97%and0.62%, respectively. The infection rate of metacercariae of Clonorchis sinensis, Metorchisorientalis were higer than others, what,s more, they were the dominant species in HeilongjiangProvince, China.The above results revealed that trematode metacercariae infection was various andcomplicated, and was widely distributed in freshwater fishes in Heilongjiang Province, China,especially Clonorchis sinensis, Metorchis orientalis which are very important zoonosestrematode, posing significant public health concern.