Veterinary Research Forum

Abstract Russian sturgeon (Acipenser gueldenstaedtii) is an endangered fish species and also an important resource for the sturgeon aquaculture industry in Turkiye. Recently, a fatal and persistent bacterial disease occurred in the reared sturgeon kept in a trout farm in Turkiye. The disease outbreak has been with notable external signs including petechial hemorrhages and systemic anemia. This outbreak lasted for six weeks, and cumulative mortality reached around 35.00 - 40.00%. In this study, no parasitic and viral agents were observed in the sturgeons. Citrobacter gillenii was isolated from the diseased fish and identified by biochemical and molecular methods including API 20E and 20NE and 16S rRNA gene region sequencing, respectively. As a result, C. gillenii was identified for the first time in Russian sturgeon in Turkiye. The sequence was also deposited under the Genbank with MW057770 accession number. According to the result of disc diffusion method, bacteria were sensitive to enrofloxacin, streptomycin, amoxicillin and oxytetracycline and resistant to penicillin, trimethoprim/sulfamethoxazole, florfenicol and erythromycin. Also, ampC, sul1 and floR resistance genes were detected in the isolated bacteria. The results of this study provide important information for the diagnosis and treatment of this newly emerged disease of Russian sturgeon.

Abstract Scuticociliates are dangerous parasitic pathogens causing systemic tissue destruction and high mortality in marine fish worldwide. In this study, the first identification of Uronema marinum (Ciliophora, Scuticociliatida) from cultured turbot (Psetta maxima) larvae using mitochondrial cytochrome c oxidase 1 (cox1) gene sequence as well as species-specific primers was reported. The mean prevalence values of infected fish were calculated, and partial sequencing obtained from the mitochondrial cox1 gene region was also compared with isolates registered in the Genbank database. The sequence comparison showed 93.00% identity to U. marinum, and the parasite has also been deposited in the GenBank database. This study is the first case of U. marinum infection in Turkish marine aquaculture, contributing to the systematics and molecular epidemiology of scuticociliate in Turkey.