Viral surveillance of cultured Rainbow Trout in the eastern Black Sea, Turkey.

To study the presence and spread of viral fish pathogens in Rainbow Trout Oncorhynchus mykiss in the eastern Black Sea region of Turkey, 172 pooled samples (seven fish per pool) of Rainbow Trout fry from 28 hatcheries were examined from December 2006 to July 2007. Forty-three pools (seven broodfish per pool) of seminal and ovarian fluids from 182 female and 119 male brood Rainbow Trout were also sampled during spawning. Moreover, reproductive fluids (22 pools) of wild trout (Salmo trutta labrax, S. t. caspius, S. t. abanticus, and S. t. macrostigma), captured by electroshocking in the rivers in and around the region, were sampled. Triplicate groups of 40 or 80 Rainbow Trout fry was also challenged with two similar isolates to determine their virulence on trout fry. Enzyme-linked immunosorbent assay was performed on the samples producing cytopathic effect on CHSE-214 cells. The positive results were confirmed with a reverse transcriptase polymerase chain reaction assay. Neither infectious hematopoietic necrosis virus (IHNV) nor viral hemorrhagic septicemia virus (VHSV) was detected during the survey. Of the 28 hatcheries sampled in the Black Sea region, 15 from six provinces tested positive for infectious pancreatic necrosis virus (IPNV) in trout fry. Unexpectedly, all reproductive fluids from both male and female cultured and wild broodstock tested negative for IPNV. Nucleotide sequences of the VP2/NS region of IPNV showed that all isolates collected (n = 38) in the region and surrounding areas belonged to the genogroup III. The findings strongly suggest that IPNV is endemic in the fry of farmed Rainbow Trout within the region. Virus prevention measures should be taken to prevent in-farm spread of these highly contagious, low-virulence isolates.