Caspian White Fish (Rutilus frisii kutum) as a host for Spring Viraemia of Carp Virus.

Rutilus frisii kutum is a fish of the Cyprinidae Family which is native in Caspian Sea and commercially cultured in Iran. This study was conducted to investigate susceptibility of Caspian White Fish to Spring Viraemia of Carp Virus (SVCV) infection and to evaluate influence of different challenge routes on virulence of the virus. Fingerlings were infected by immersion, intra-peritoneal (i.p.) injection, cohabitation and orally. Dead and surviving fish were collected for histological examination as well as for virus re-isolation by cell culture, Reverse Transcriptase Polymerization Chain Reaction (RT-PCR) and Indirect Fluorescent Antibody Test (IFAT) analysis. The results indicated that immersion was the best infectious route of transmission with the highest mortality, whereas oral transmission showed the lowest mortality. The virus was also re-isolated from dead fish and identified by IFAT. In addition, histopathological changes including branchial, hepatic and splenic necrosis as well as glomerulonephritis and necrosis in kidney were observed in diseased fish tissues but not in the survivors. RT-PCR on samples obtained from surviving fish tissues detected viral genome in the fish surviving from immersion, i.p. injection and cohabitation challenges but not in the fish infected orally. In conclusion, Caspian White Fish are susceptible to infection by SVCV and virulence of the virus could be influenced by route of transmission. In addition, SVCV could persist in surviving fish, which may serve as reservoirs of the virus, transmitting infection to healthy fish population.

Experimental susceptibility of Caspian white fish, Rutilus frisii kutum to Spring viraemia of carp virus.

Caspian white fish (Rutilus frisii kutum) is a fish of the family Cyprinidae, which is commercially harvested from the Caspian Sea. Experimental infection with Spring viraemia of carp virus (SVCV) was conducted in order to examine susceptibility of caspian White Fish and clinical impacts of infection. Fingerling fish were injected intra-peritoneally or waterborne-exposed with SVCV and were monitored daily for 7 weeks. Dead fish and those survived at the end of experimental period were collected for virus isolation and reverse transcriptase polymerase chain reaction analysis. Epithelioma papulosum cyprini cell line was used to re-isolate the virus and indirect fluorescent antibody test was conducted to identify the isolated virus. Infection trials showed that SVCV was highly pathogenic for the Caspian White Fish with mortality rate ranging from 75 to 85 %, depending on the viral challenge model. SVCV genome was detected from dead and apparently healthy fish tissues of both virus exposure models, which showed Caspian White Fish not only can be regarded as a susceptible host, but also serve as a vector of the virus.

Molecular epidemiology of zoonotic streptococcosis/lactococcosis in rainbow trout (Oncorhynchus mykiss) aquaculture in Iran.

BACKGROUND AND OBJECTIVES: Streptococcosis/lactococcosis is a hyperacute systemic disease that can occur in marine and fresh waters of many species of fish. The aim of this work was to study the disease outbreak in the major rainbow trout (Oncorhynchus mykiss) production of Iran. MATERIALS AND METHODS: 108 Gram positive cocci isolates were obtained from diseased trout in seven provinces with major trout production during 2008 till 2009. These bacterial isolates were characterized using phenotypic and molecular studies. The isolates were also analysed phylogeneticaly and compared with the available data. RESULTS: 49 samples (45.37%) were identified as Streptococcus iniae, 37 samples (35.2%) matched with Lactococcus garvieae; and 22 samples (19.43%) were identified as members of Streptooccus genus by culture-based and biochemical tests of API 50 CH, API 20 STREP and rapid 32 STREP systems. Using universal primers for differentiation of Streptococcus sp. and Enterococcus sp, all 108 samples were identified as Streptococcus sp. with a target region of 500 bp. Single specific PCR resulted in identification of 64 (59.2%) isolates as S. iniae and 44 (40.8%) isolates as L. garvieae. The phylogenetic analysis of the S. iniae isolates resulted in maximal similarity to some strains reported from Taiwan and to all Brazilian strains. Also, one strain showed less sequence similarity values with other tested strains although this strain has high similarity with ATCC 29178 strain, all reported Chinese, and some Taiwanian strains. Also, analysis of S. iniae LctO gene sequence showed that this isolate clustered within the S. iniae group. The sequence analysis of L. garvieae strains also showed that they have maximum similarity to all Japanese and Chinese strains, but one strain has lower sequence similarity values with all other recorded strains. CONCLUSION: [corrected] The results of this study clearly show that trout farming in Iran is severely affected by both species of S. Iniae and L. garvieae and requires serious preventive criteria.