虾肝肠胞虫(EHP)在凡纳滨对虾养殖水环境中的分布情况及传播途径初步研究

摘要

针对近年来在舟山地区养殖户普遍反映的凡纳滨对虾感染虾肝肠胞虫(EHP)情况,本实验室运用巢式PCR检测方法,对凡纳滨对虾养殖水环境中EHP分布情况开展了调查;同时以携带EHP对虾对健康凡纳滨虾进行了人工感染试验,分析EHP在水体中的传播途径.实验结果表明,从采集的虾、蟹类和水样本中均扩增出了EHP,经测序比对与GenBank中EHP序列一致;其中虾类样本最高,阳性率达17.6%,而采集的水样中,从对虾携带EHP的养殖塘采集的水样阳性检出率最高,为100%;人工感染试验中,活病虾肝胰腺组织投喂组EHP的阳性检出率是45.8%,投喂冷冻病虾肝胰腺组的阳性检出率是12.5%,健康虾和病虾混合饲养组的阳性检出率是54.2%,对照组未有EHP检出.通过上述研究,初步认为EHP一旦在养殖水环境存在,即可以通过流水分布于养殖环境中,不仅在养殖水体中存在,还可以在其它水生生物体内存活;健康虾可以通过摄食寄生EHP的病死虾或养殖水环境中的孢子体而感染.%Enterocytozoon hepatopenaei (EHP), a serious pathogen associated with retarded growth in cul-tured shrimp, has been reported to be prevalent in Zhoushan of Zhejiang province. Aquatic animals in the wild and water taken from the aquaculture pond and natural environment were both detected by nested polymerase chain reaction in order to investigate the distribution of EHP in aquatic environment. To study the possible transmission routes of EHP, the healthy shrimp (Litopenaeus vannamei) were infected artificially by the EHP-tainted shrimp, which kept in different ways. The results showed that the PCR yielded an expected product of 223 bp and the sequences showed 100% identity with the other EHP genes had been reported from GenBank. The detection rates of EHP in wild shrimps and crabs which collected from natural environment were 18.5% and 8.7%, but no EHP had been found in all of the 17 fish samples. Water collected from EHP-tainted pond showed higher prevalence of EHP (100%) compared to those from the natural environment (0%). The positive rate of detection of EHP nucleic acid was 12.5% in the experimental group within 35 days after fed with frozen EHP-infected shrimp, 45.8% in the group fed with fresh EHP-infected shrimp, but 54.2% in the experiment group which farmed with tainted shrimp. The findings of suggested that the EHP release to the environment by infected shrimps could distribute in the shrimp ponds by water flowing and infect other crustacean lived in the same environment, too. Laboratory oral challenge trials revealed that EHP could cause horizontal transmission to uninfected shrimp.