Development of a duplex PCR for the simultaneous detection of EHP and IHHNV and analysis of the correlation between these two pathogens.

Infectious hypodermal and hematopoietic necrosis virus (IHHNV) is one of the linearly single-stranded DNA viruses. Ecytonucleospora hepatopenaei (EHP) is an intracellular parasitic microsporidian. IHHNV and EHP are pathogens that have been widely prevalent in shrimp farming. Both of them are associated with growth retardation of the penaeid shrimp, which causes serious economic losses to shrimp farming. Shrimp can be co-infected with IHHNV and EHP. In this study, a rapid duplex polymerase chain reaction (PCR) was developed and optimized for the simultaneous detection of EHP and IHHNV. The detection limit of the duplex PCR could reach 1.5 × 102 copies for EHP and IHHNV. A total of 578 Litopenaeus vannamei samples were detected by the established duplex PCR detection method. The results suggested that 398 samples were infected with EHP, 362 samples were infected with IHHNV, and 265 samples were co-infected with EHP and IHHNV. The case-control analysis of the detected shrimp samples showed a certain synergistic effect between EHP and IHHNV.

Study of infectious hypodermal and hematopoietic necrosis virus (IHHNV) infection in different organs of Penaeus vannamei.

Infectious hypodermal and haematopoietic necrosis virus (IHHNV) is a major viral pathogen in cultured shrimp. It is generally believed that the target organs of IHHNV in shrimp include tissues of ectodermal and mesodermal origin, but do not normally include organ systems of endodermal origin, such as hepatopancreas. In this study, the feeding challenge of IHHNV in different organs (pleopods, muscles, gills, and hepatopancreas) of Penaeus vannamei was studied. The PCR results showed that hepatopancreas of P. vannamei had the strongest IHHNV positivity (100% positive, 19.4 copies/mg) in the feeding challenge experiment. Gills and pleopods had similar infectivity to IHHNV (86.7% positive, 10.6 and 10.5 copies/mg). Among the four organs tested in this study, the IHHNV positivity of muscles was the weakest (33.3% positive, 4.7 copies/mg). The IHHNV infection to hepatopancreas of P. vannamei was also histological confirmed. Our current data indicated that the shrimp tissues derived from the endoderm such as hepatopancreas could also be infected by IHHNV.

Development of a PCR assay for the effective detection of Enterocytozoon hepatopenaei (EHP) and investigation of EHP prevalence in Shandong Province, China.

Enterocytozoon hepatopenaei (EHP), a recently reported pathogen in the penaeid shrimp, is spreading widely and seriously threatening Penaeus (Litopenaeus) vannamei aquaculture. This study aimed to develop a new and more sensitive polymerase chain reaction (PCR) method for the effective detection of EHP. An EHP PCR assay with a pair of primers specifically amplifying a 358 bp EHP DNA fragment was developed, which was demonstrated to be capable of detecting as low as 2 × 101 copies of EHP and is specific for EHP without cross reaction with DNA samples prepared from five common shrimp pathogens, including white spot syndrome virus (WSSV), infectious hypodermal and haematopoietic virus (IHHNV), hepatopancreatic parvovirus (HPV), infectious myonecrosis virus (IMNV), and yellow head virus (YHV). This new assay is more specific and more sensitive than the previously published EHP PCR methods. With the PCR assay developed in this study, we investigated the prevalence of EHP in four areas of Shandong, China by testing a total of 639 shrimp samples collected from Yantai, Binzhou, Dongying, and Weifang. The results showed that the EHP positive rate reached 51.2%, indicating that EHP is prevalent in shrimp culture in China.

Research progress on hosts and carriers, prevalence, virulence of infectious hypodermal and hematopoietic necrosis virus (IHHNV).

Infectious hypodermal and hematopoietic necrosis virus (IHHNV) is one of the major viral pathogens of penaeid shrimp and it has spread worldwide. IHHNV causes substantial economic loss to the shrimp farming industry and has been listed as a notifiable crustacean disease pathogen by the World Organization for Animal Health (OIE). In this paper, we reviewed studies on the hosts and carriers, prevalence, genotypes and virulence of IHHNV. The pathogenesis mechanisms of IHHNV and the viral interference between IHHNV and white spot syndrome virus (WSSV) were also discussed. The mechanism of IHHNV infection and its virulence difference in different hosts and different developmental stages have not been fully studied yet. The mechanisms underlying viral interference between IHHNV and WSSV are not yet fully understood. Further studies are needed to elucidate the precise molecular mechanisms underlying IHHNV infection and to apply the insights gained from such studies for the effective control and prevention of IHHNV disease.

[Analysis of genetic variation of abalone (Haliotis discus hannai) populations with microsatellite markers].

Microsatellite markers were used to access the genetic variation in three populations of abalone Haliotis discus hannai. Two wild populations were collected from the sea areas in Changdao, Shandong and Dalian, Liaoning respectively. A cultivated population originated from the sea area in Kongdongdao, Shangdong. Six microsatellite loci were screened for genetic polymorphism. Polymorphic information content (PIC) value per loci was greater than 0.5 and can be used to analysis of genetic structure of the three abalone populations. Fifty-seven alleles were amplified from the three populations in six microsatellite loci. The average number of alleles (A) was 9.50 and the effective number of alleles (Ne) was 5.8572. The mean observed heterozygosity (Ho) and the mean expected heterozygosity (He) were 0.6925 and 0.7966, respectively. The Ho and He of two wild abalone populations were higher than that of cultured population. All these results provide a basis for conservation and utilization of genetic diversity of Haliotis discus hannai.