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A Survey of Viral Diseases in Farmed Salmonids in Croatia

The overall annual production of Salmonid species in Croatia is about 1500 tons. The main cultivated species are rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta fario). The control of fish viral diseases listed by OIE is performed according to the “ Decree on the measures of animal health protection against infectious and parasite diseases“ issued yearly by Ministry of Agriculture, Forestry and Water Management. A field survey was carried out to study the occurrence and distribution of viruses causing diseases of major impact in salmonid farming, namely viral haemorrhagic septicaemia (VHS), infectious haematopoietic necrosis (IHN) and infectious pancreatic necrosis (IPN) in farmed salmonids. The presence of VHS virus (VHSV), IHN virus (IHNV) and IPN virus (IPNV) in the tissue samples was tested by virus isolation in cell cultures, and subsequent virus identification by virus neutralisation, ELISA tests and immunoperoxidase tests. The samples of spawning products and salmonid fry are collected at the farms and submitted to the Laboratory. During last five years there were no findings of mentioned viral diseases in Croatian salmonid farms. Apart from those results there was an occurrence of viral hemopoietic necrosis in imported rainbow trout fry situated in quarantine facility at the one farm. The IHNV was isolated in EPC and BF2 cell cultures, identified by immunoperoxidase test and confirmed by PCR. The « partial stamping out» was performed at the rainbow trout farm and the other fish were subjected to the continuous control for the presence of the virus. It seems that the « partial stamping out» method was successful because ten months later the results of virological examination of the samples from all categories of rainbow trout from the mentioned farm were negative.

Salmonids; Viral diseases; Survey

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