New bacterial infections that have emerged in fish in Poland

摘要

The aim of the study was to present the reasons for the emergence and an overview of new bacterial infections in freshwater fish diagnosed in Poland over the last several years. One of the main reasons is ecological changes in freshwater ecosystems as a result of the degradation of these environments. The progressive degradation of these ecosystems is largely due to human activity associated with the development of civilization, which results in the production of greater amounts of sewage of different origin. Also some factors independent of human activity have a major influence of degradation and variability in freshwater environments; for example climate change, geographical conditions and the effects of natural disasters. In fish farming conditions, additional factors contributing to the emergence of new diseases/pathogens are the use of antibiotics and disinfectants. Moreover, the introduction of new fish species carries many risks. For several or even a dozen years, some new infections in freshwater fish cultured in Poland have been diagnosed. They are caused by bacteria which were not previously known as fish pathogens, or infections formerly diagnosed in many other countries, while in Poland they emerged relatively recently. The first group includes infections caused by Acinetobacter lwoffii, A. johnsonii and Shewanella putrefaciens. Both cyprinids as well as salmonids fish cultured in Poland are sensitive to these infections. Among these microorganisms, S. putrefaciens are most frequently diagnosed, causing losses of up to 20% of the infected population. The second group includes bacteria from the genera Serratia and Streptococcus. These microorganisms primarily affect salmonids. In the case of infections Serratia spp, losses may reach up to 35%. In populations of fish infected with Streptoccoccus spp. losses are between 5% and 15%. Data presented in this article suggest the need for a new approach by diagnosticians to identify fish diseases. Currently, laboratory diagnosis must take into account not only the presence of bacteria well known as pathogens of fish as potential etiological factors of disease, but also those less well-known in Poland or completely new ones.