Particularly dangerous bacterial pathogens in freshwater industrial fish farming in the north-west of Russia

Freshwater aquaculture in northwestern Russia, including the Republic of Karelia and the Leningrad, Vologda, and Murmansk regions, primarily specializes in the farming of salmonids (Salmo, Oncorhynchus, Salvelinus) and whitefish (Coregonus). With production intensifying, the natural properties of water bodies changing, and the region’s unique hydroclimatic conditions, bacterial infections are becoming the most widespread and economically significant threat to the industry. The aim of this study is to systematically analyze current data from international genetic databases on the etiology and molecular genetic mechanisms of virulence, as well as to analyze scientific publications on the epidemiology and economic significance of leading bacterial pathogens in freshwater aquaculture in northwestern Russia. A systematic analysis of genetic databases (NCBI GenBank, UniProt) on leading bacterial pathogens in freshwater aquaculture under cold-water fish farming conditions was conducted. The most dangerous nosologies are considered, such as salmon furunculosis (Aeromonas salmonicida subsp. salmonicida), cold-water disease (Flavobacterium psychrophilum), red mouth disease (Yersinia ruckeri), bacterial kidney disease (Renibacterium salmoninarum), and columnaris (Flavobacterium columnare). The molecular genetic determinants of virulence for each pathogen are examined, including the type III (T3SS) and type VI (T6SS) secretion systems, the main toxins, and adhesion factors. The increasing role of antibiotic resistance, including horizontal transfer of resistance genes, as a systemic threat in the context of the One Health concept is demonstrated. A conclusion is drawn regarding the need to introduce multiplex molecular diagnostics, regular genomic surveillance of circulating strains, and improved biosecurity on fish farms into domestic practice.

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