Features of bacterial diseases of rainbow trout in industrial farms in North-West Russia

Abstract

Studies of the parasite fauna of rainbow trout have revealed a number of pathogens of parasitic diseases at enterprises that use open water bodies as sources of water supply. Of the parasitic protozoa, the most dangerous is Ichthyophthirius multifiliis. This is due to the presence of a free-living stage in this ciliate, as well as to the possibility of localization under the fish scales. Of the helminthiases that occur in rainbow trout during artificial cultivation on the farms of the North-West region of Russia, the most problematic are monogenes and cestodes, which cause gyrodactylosis and trienophorosis. The plerocercoids of the cestode Triaenophorus crassus, in particular, are localized in the musculature of fish and, with a high degree of invasion, trout loses its commercial value. In the presence of a focus of parasitic diseases in natural reservoirs, wild fish are a reservoir of invasion, aquatic invertebrates (planktonic crustaceans, molluscs) are the most important element of the parasite-host system, and fish-eating birds, being the final host, contribute to the spread of invasions. In cage farms, due to the peculiarities of the cultivation technology, the fight against parasitic protozoa is extremely difficult and requires significant labor costs. In basin farms, on the contrary, the design of fish-breeding tanks and the water supply system allows for the most efficient implementation of therapeutic and prophylactic measures. Nevertheless, outbreaks of parasitic diseases can be observed in violation of the cultivation technology (overcompaction of the planting, violation of the feeding regime, etc.). Control of the epizootic state makes it possible to identify infection and carry out a set of necessary therapeutic and preventive measures.