aInstitute of Biology, Karelian Research Centre, RAS
Pushkinskaya, 11, Petrozavodsk, Karelia, 185910 Russia
*e-mail: provotorov.ds@mail.ru
Ulcerative dermal necrosis (UDN) in salmonids is a severe disease of mature salmonids characterized by abundant mortality of the infected fishes. The necrosis is associated with skin ulcers emergence, which are further affected by secondary pathogens (for example, by oomycetes of the Saprolegnia genus or various pathogenic bacteria), and ultimately leads to death. The disease named “salmon disease” was registered in the XIX century, then it was noted periodically till the 1960s, when the infection was detected in southwestern Ireland, and afterward spread to the rivers of the British Isles and neighboring countries. Currently, the cases of mass salmon infection outbreaks depend on the season and the region. In recent years, reports on increased sickness rate of salmonids have been received from a number of countries, including Sweden, Finland, Russia, and others. It should be noted that only half of the fish with UDN-like lesions were specifically diagnosed as UDN based on all diagnostic criteria of this disease. Considering this fact, and also taking into account the detection of new symptoms in infected fish, including red spots on the skin, a rash in the abdomen, skin bleeding, a new disease has been revealed. This one has got the name “Red Skin Disease” (RSD) and now it has its own diagnostic criteria as well as UDN. The registration of the new disease and approval of its name was made at a scientific seminar at the Norwegian Institute of Nature (NINA, Norway) in November 2019. Attempts to find out the UDN etiology have been made since the 60s of the XX century. Despite the fact that most researchers consider the nature of the disease to be viral, there is no clear scientific evidence for this. It should be noted that there are extremely little convincing data about the origin, etiology, pathogenesis, and possible consequences of this dangerous disease, so it is necessary to expand comprehensive interdisciplinary research using modern experimental and communication methods. It will allow developing of effective measures to deal with this disease and propose a system for monitoring and predicting the future state of Atlantic salmon populations.
