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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.
The article describes the major findings concerning the occurrence of previously unrecognized infection with a virus provisionally named “Schmallenberg virus” (SBV) in Germany, the Netherlands, Belgium and Great Britain. The virus belongs to the family Bunyaviridae, genus Orthobunyavirus, serogroup Simbu. Full-length genome sequencing has shown its highest genetic similarity to Shamonda and Akabane viruses. The viruses of this group are transmitted mainly by mosquitoes (Culicidae) and midges (Culicoides) with very limited direct transmission from animal to animal (mostly transplacental transmission from a dam to the foetus during pregnancy). The clinical manifestation of the Schmallenberg virus infection has been associated with non-specific clinical signs in adult cattle (fever, reduced milk yield, diarrhoea), whereas congenital malformations (hydrocephalus with brain hypoplasia, arthrogryposis) have been observed in newborn lambs. For diagnostic purposes, RT-PCR, virus neutralisation and indirect immuno-fluorescence tests have been developed. The latter two assays cannot be applied for large-scale testing, but an assay for serological screening is currently unavailable. The major conclusion of the preliminary risk assessment performed by the European Centre for Disease Prevention and Control (ECDC) is that the threat to human health is very unlikely but cannot be excluded at this stage. None of the infections caused by the viruses of the Simbu serogroup are included in the list of diseases subjected to international notification, but affected countries have notified OIE of the occurrence of SBV infections according to regulations applicable to new and emerging diseases.
Bats are the only mammals that have the ability to fly. In recent years, many emerging and re-emerging diseases threaten humans and animals, raising fear. Studies carried out confirm that many serious diseases are caused by viruses such as: EboV, Marburg, MERSCoV, SARS, Hendra and Nipah, the source of which are bats. Although the bats do not have very close contact with humans viruses are transmitted through intermediate hosts. Changes in the environment caused by human activities lead to increased contacts between humans and animals resulting in a higher risk of infection.
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