The Epidemiology Of Enterocytozoon Hepatopenaei And Study Of Prevention And Control Techniques In Shrimp

In recent years,there are more and more reports on retarded growth in shrimp in Southeast Asia.Enterocytozoon hepatopenaei(EHP)was detected in most of these slow-growing shrimps.It was firstly found in the slow growing Penaeus monodon cultured in Thailand in 2004 and officially named in 2009.It is believed that the effect of EHP on the growth of shrimp leads to enormous economic losses in the aquaculture industry.In this study,through the evaluation on the detection of EHP with pooled samples,tracking detection and preliminary screening test of drugs about the prevention and treatment of EHP.We aimed to establish an efficient and fast detection method of EHP,analyze the dynamic changes about the EHP in the whole breeding process,clarify the actual breeding production factors that influence the EHP and select several effective drugs for EHP.TaqMan probe qPCR assay was established in our laboratory to detect EHP in earlier stage.This method conforms to the quantitative detection of samples,as well as can be used to detect the actual samples quantitatively.However,in the method of quantitative detection,because of the large sample size in the epidemiological survey,each sample was tested with a single tail,and the workload was huge.Therefore,in order to reduce testing workload and cost,and improve the coverage of epidemiological investigation,this paper evaluated a kind of pooled samples detection method that based on TaqMan qPCR detection,and expected to use the technology to detect the next shrimp samples.This method greatly reduces the detection time,saves the detection cost and provides a simple and quick method for the epidemiological study of EHP in shrimp.In order to verify the dynamic changes about the EHP in the whole breeding process,this study conducted a sustained investigation on two shrimp farms from Haiyang and Weifang,Shandong Province,measured the breeding shrimp growth parameters at several time points in the whole breeding process,tested the EHP infection loads in two farms at several time points with TaqMan qPCR.The results showed that there were different changes in EHP positive rate and loads of two groups in different breeding time,and there were significant differences in EHP variation.The relationship between the length and the EHP loads was analyzed,the results showed that the EHP loads and shrimp growth doesn’t necessarily show the fixed correlation characteristics at some point in the process of cultivation.However,according to the analysis of normal peak subgroup,the negative correlation between EHP logarithm and body length can be expressed in this subgroup.Moreover,the main body part of each batch showed that the negative correlation was significant(P<0.05)or extremely significant(P<0.01).This can explain the that the EHP and shrimp growth parameters of the group showed significant negative correlation by the previous studies.The distribution of EHP logarithm of the samples collected at different culture stages of two populations was Gaussian distribution analysis.In the range of EHP logarithm of the positive samples of the two groups,the HY population was generally larger than the WF population in the same period.This shows that the levels of EHP infection in each stage of the WF population are relatively close,and the level of EHP infection in the HY population is quite different during the corresponding period.There are no public reports of EHP effective drugs.In this study EHP drug screening was carried out in the previous work,and two kinds of effective insect repellents for EHP were found for the first time.Both drug soaking and feeding can effectively reduce the parasite loads of EHP in shrimp.This paper analyzed the changes of EHP load before and after medication by breeding experiment.A preliminary screening of EHP effective drugs was carried out.This provides basic data for further study on prevention and treatment of EHP drugs.