Surveillance of viral fish diseases in the Czech Republic over the period January 1999 - December 2006

The present study reports the results of virological survey in fish with an emphasis on the diseases included in the Czech National Legislation. Monitoring of fish both without symptoms and with a manifested disease was performed within this virological surveillance. Between January 1999 and December 2006, viral haemorrhagic septicaemia virus (VHSV), infectious haematopoetic necrosis virus (IHNV) and infectious pancreatic necrosis virus (IPNV) were surveyed by the National Reference Laboratory for viral diseases on fish. Among of 3789 sample pools processed, VHSV was detected in seven cases (6× in Oncorhynchus mykiss, 1× in Salmo trutta m. fario), IHNV was detected in seven cases (6× in Oncorhynchus mykiss, and 1× in Esox lucius) and IPNV was diagnosed once in Oncorhynchus mykiss. In four cases, the viral agents were detected in ovarian fluid from broodfish without any clinical symptoms. In the remaining cases the virus was isolated from tissue homogenates. Our results show that ovarian fluid is valuable material for the detection of viral agents during the monitoring of fish diseases.