INVASION OF FISH BY LARVAE OF THE FAMILY DIPHYLLOBOTHRIIDAE IN THE KHANTY-MANSI AUTONOMOUS OKRUG – YUGRA

Two epidemiologically significant species of the tapeworm (D. latum и D. dendriticum) circulate in of the Ob-Irtysh basin within the Khanty-Mansi Autonomous Okrug. They have an unequal effect on the human body. The purpose of the science work is to determine the invasion of fish by larvae of tapeworms D.latum and D.dendriticum (Perch Perca fluviatilis, Ruff Gymnocephalus cernuus, Pike Esox lucius, Syrok Coregonus peled, Muksun Coregonus muksun, Nelma Stenodus leucichthys nelma) from waterbodies of the Ob River and its tributaries from 2013 to 2019 year. The study aim is to identify the main factors of transmission of the invasion (diphyllobothriasis) to population. The fish for parasitological research and species identification was caught in the Ob River and its tributary, the Vakh River, as well as Torm-Emtor Lake. The studies were carried out in the parasitological laboratory of the Center for Hygiene and Epidemiology in the Khanty-Mansi Autonomous Okrug – Yugra, Nizhnevartovsk, the Nizhnevartovsk District, in Megione and Raduzhny by the method of incomplete helminthological study of fish. The study results found in general a very high level of plerocercoid invasion of fish from the Ob and Vakh Rivers. It was noted that the pike had a significantly high percentage of infection with D. latum, 71.64%. The highest intensity of invasion and localization of larvae (the family Diphyllobothriidae) was on the abdominal wall of the fish, and then on walls and in the thickness of walls of esophagus and stomach, in eggs, and very few in muscle tissues.

Materials on multicellular parasites fauna of the ruffe Gymnocephalus cernuus Linnaeus, 1758 (Pisces: Percidae) from the Saratov water basin

Objective of research. Data on the species composition of the fauna of multicellular parasites and the infection rates of the pope ruffe Gymnocephalus cernuus Linnaeus, 1758 from Mordovian floodplain of the Saratov reservoir (the middle part) are pesented. Materials and methods. 53 ruffe individuals were investigated in spring and summer 2012 – 2015 by incomplete parasitological post-mortem examination (Bykhovskaya-Pavlovskaya, 1985). 19 species of multicellular parasites belonging to 7 classes: Monogenea - 1, Cestoda - 1, Trematoda - 11, Nematoda - 3, Acanthocephala - 1, Bivalvia - 1, Crustacea – 1 were registered. The largest group are flukes; more than half of species (8) are larval forms, which is the result of bottom living of the host. The significant diversity of larval stages of helminths (8 species of trematodes and 2 species of nematodes) shows the involvement of the ruffe as an intercalary, supplementary and/or reservoir host in the circulation of parasites in fish, birds and mammals. 7 species of parasites infest the ruffe on the food chain; 12 species – using the active infestation way. Results and discussion. The studied parasite fauna contains one species narrowly specific for the ruffe (monogenea D. amphibothrium (Wagener, 1857) and 2 species typical for percoid fishes (cestoda Proteocephalus percae (Müller, 1780) and trematoda Bunodera luciopercae (Müller, 1776). 2 alien species Nicolla skrjabini (Iwanitzky, 1928) (marita) and Apophallus muehlingi (Jägerskiöld, 1898) (mtc.) whose natural habitat is limited by the rivers of the Azov-Black Sea and Baltic Sea were registered in the fauna of multicellular parasites of the ruffe from the Saratov reservoir. The most common ruffe parasites are Diplostomum and Ichthyocotylurus metacercariae metacercaria infesting fish by penetrating through the body covers. These metacercariae as well as Apophallus muehlingi metacercariae are pathogenic to fish.