Search

Background: A virus was isolated from diseased turbot Scophthalmus maximus in China. Biophysical and biochemical assays, electron microscopy, and genome electrophoresis revealed that the virus belonged to the genus Aquareovirus, and was named Scophthalmus maximus reovirus (SMReV). To the best of our knowledge, no complete sequence of an aquareovirus from marine fish has been determined. Therefore, the complete characterization and analysis of the genome of this novel aquareovirus will facilitate further understanding of the taxonomic distribution of aquareovirus species and the molecular mechanism of its pathogenesis. Results: The full-length genome sequences of SMReV were determined. It comprises eleven dsRNA segments covering 24,042 base pairs and has the largest S4 genome segment in the sequenced aquareoviruses. Sequence analysis showed that all of the segments contained six conserved nucleotides at the 5' end and five conserved nucleotides at the 3' end (5'-GUUUUA ---- UCAUC-3'). The encoded amino acid sequences share the highest sequence identities with the respective proteins of aquareoviruses in species group Aquareovirus A. Phylogenetic analysis based on the major outer capsid protein VP7 and RNA-dependent RNA polymerase were performed. Members in Aquareovirus were clustered in two groups, one from fresh water fish and the other from marine fish. Furthermore, a fusion associated small transmembrane (FAST) protein NS22, which is translated from a non-AUG start site, was identified in the S7 segment. Conclusions: This study has provided the complete genome sequence of a novel isolated aquareovirus from marine fish. Amino acids comparison and phylogenetic analysis suggested that SMReV was a new aquareovirus in the species group Aquareovirus A. Phylogenetic analysis among aquareoviruses revealed that VP7 could be used as a reference to divide the aquareovirus from hosts in fresh water or marine. In addition, a FAST protein with a non-AUG start site was identified, which partially contributed to the cytopathic effect caused by the virus infection. These results provide new insights into the virus-host and virus-environment interactions. [ABSTRACT FROM AUTHOR]

Aeromonas veronii is abundant in aquatic environment and could cause diseases in various kinds of aquatic animals. However, few cases of A. veronii infection were reported in largemouth bass (Micropterus salmoides), which has been widely farmed and become an important economic fish species in China in recent years. In this study, a strain of Gram-negative bacteria was isolated from the diseased largemouth bass, and was tentatively named strain HN1903. According to the results of biochemical characteristics, 16S rRNA sequencing analyses, and artificial infection experiment, the isolate was identified as A. veronii. The virulence of strain HN1903 was tested by challenge experiments, and the value of LD 50 with intraperitoneal injection was 3.72 × 104 CFU/g fish weight. Eight virulent genes, including ae rA, gca T, act , fla , lip , ser , hly A, and ahy B were screened by PCR assay. Antibiotic resistance results showed that the isolate was susceptible to gentamicin and cefotaxime, and moderately sensitive to florfenicol and streptomycin based on the 12 antimicrobial agents tested. Histopathology examination indicated the necrosis in liver, kidney, and gill, inflammatory cellular infiltration in kidney, and hemosiderin granules increase in spleen. In this study, A. veronii was isolated, identified, and its pathogenicity was clarified. The findings in this study could provide the strategy of fish disease control, preventing the outbreak of A. veronii infection. • A new bacterial strain named HN1903 was isolated from farmed largemouth bass with ulcerative lesions. • The bacterial strain was identified as Aeromonas veronii with 8 virulent genes. • The isolate was susceptible to gentamicin and cefotaxime, and moderately sensitive to florfenicol and streptomycin. • Histopathology indicated the necrosis in liver, kidney, and gill. [ABSTRACT FROM AUTHOR]

Red swamp crayfish Procambarus clarkii is an economically important species that is widely cultivated throughout China. With the application of high-density culture, P. clarkii is usually infected by different pathogens in water. Co-infection with multiple pathogens was common, which has resulted in greater economic loss than single infections. In this study, we investigated a case of co-infected crayfish with bacterial and viral pathogens at a local farm. Firstly, a bacterial strain was isolated from the gills of infected crayfish. According to the results of 16S rRNA sequence and analysis of the Biolog Gen III MicroPlate system, the isolated bacterial strain was finally identified as Aeromonas veronii. The isolated A. veronii exhibited significant virulence to crayfish, with an LD 50 value of 6.04 × 106 CFU/crayfish. As a result, drug sensitivity tests showed that the isolated A. veronii was completely resistant to ampicillin, penicillin, and compound sulfamethoxazole tablets, and highly sensitive to seven kinds of antibiotics. Furthermore, white spot syndrome virus (WSSV) was also detected from the gill tissue of diseased crayfish by polymerase chain reaction. After experimentally co-infected with A. veronii and WSSV, the healthy P. clarkii presented similar clinical and histopathological signs with natural infected P. clarkii. The mortality of the co-infected group was 100%, which was higher than that in the group single infected with A. veronii (70%) or WSSV (83.3%). In summary, a case of co-infection with WSSV and A. veronii from P. clarkii was comprehensively studied in this study. The results will supply an effective diagnosis strategy for the co-infection, and provide therapy reference to prevent and control P. clarkii disease. • A case of co-infection with different pathogens was investigated in P. clarkii. • WSSV and Aeromonas veronii were identified from the gills of P. clarkii , respectively. • The co-infection accelerates the course of disease. • The results will supply diagnosis strategies for co-infection and provide therapy reference to control P. clarkii disease. [ABSTRACT FROM AUTHOR]

A new grass carp reovirus strain, tentatively named GCReV-109, was isolated in Hubei, China, and its complete genome sequence was determined. The genome contained 11 double-stranded RNA segments (S1-S11) covering 24,620 base pairs. All of the segments had conserved terminal nucleotides, with GUAA(U)/CU at the 5' end and UCAUC at the 3' end. Protein sequence comparison showed that GCReV-109 was most closely related to GCRV-GD108 and shared 96.6-99.5 % protein sequence identity but only shared 16.7-46.1 and 15.1-45.4 % identity with GCRV-873 and HGDRV, respectively. Phylogenetic analysis showed that grass carp reovirus strains in China can be divided into three genotypes. Further analysis revealed homology between the GCRV-109 VP56 and HGDRV VP55 proteins, as well as GCReV-109 NS38, GCRV-873 NS38, and HGDRV VP39. The results of these comparisons also indicated that the homology between viruses was not necessarily linked to their geographical distribution. Our study will help in recognizing and understanding the genome structure and genetic diversity of grass carp reovirus.

A moribund juvenile Yangtze finless porpoise (Neophocaena phocaenoides) with skin lesions and ulceration was found in Dongting Lake, China. Pathologic examination, electron microscopy, and polymerase chain reaction of liver tissue revealed widely distributed necrotic lesions, sinusoidal dilatation, congestion and herpes-like virus particles.