Helminthofauna and the level of infection of the main commercial species of semi-migratory and riverine fish in the lower zone of the Volga delta

Abstract

On the territory of the Volga Delta and the northern part of the Caspian Sea, there are natural epizootic foci of anisakiosis, corynosomiasis, eustrongilidosis, pseudamphistomosis and opisthorchiasis. Many species of commercial semi-migratory and riverine fish have a high epidemiological significance. Therefore, monitoring the level of their infection with larvae of pathogens of anthropozoonosis is very relevant. The aim of the work was to determine the qualitative composition of epidemiologically significant helminth fauna and the level of infection with pathogenic helminth larvae of the main commercial species of semi-aquatic and riverine fish in the lower zone of the Volga delta in modern conditions. The material for the study was 660 copies . mature commercial fish of eight species, the study of parasitic purity of which was carried out by the method of incomplete helminthological research in accordance with the requirements of regulatory documents of the Russian Federation. The qualitative composition of the epidemiologically significant component of the helminth fauna was represented by seven species. All examined fish species are infested with larvae of pathogenic helminths. The maximum species diversity of dangerous parasites was found in the roach (5 species), the minimum — in the bream (1 species). The localization of helminth larvae was diverse, but most of the identified pathogenic species also invaded the muscle tissues of fish. The exceptions were Anisakis schupakovi and Corynosoma strumosum, which were located only in the abdominal fat and internal organs of the examined representatives of the ichthyofauna. Parasitological parameters of infection with dangerous parasites in different species of hydrobionts differed significantly. The larvae of the nematodes A. schupakovi and Eustrongylides excisus were characterized by the maximum distribution, while the frequency of their occurrence prevailed in predatory fish. Metacercariae Apophallus muehlingi dominated in number. The rarest representative of the community of pathogens of biohelminthiasis was C. strumosum, which was parasitized only in walleye. Most of the identified pathogenic organisms were viable, which indicated the need for mandatory disinfection of fish before sale.