Objective of research: The purpose of the study is to investigate the influence of Ligula intestinalis plerocercoids on linear growth of roach Rutilus rutilus in the Chivyrkuysky bay of the lake Baikal. Materials and methods. Roach was caught on a permanent station in the Monakhovo creek of Chivyrkuysky bay of the lake Baikal at the same time interval (June 25-July 5) in 1997-2005. The analysis of roach infection with L. intestinalis plerocercoids was performed based on incomplete parasitological dissections of 807 host specimens at the age of 0+ to 10+. Standard body length (the distance from the tip of the snout to the anterior end of the caudal fin) was used to characterize the linear growth of roach. Results and discussion. L. intestinalis plerocercoids wasn’t found out in underyearlings (0+) of roach. The host began to be infected with this tapeworm at the age of 1+. The maximum infection level with L. intestinalis plerocercoids was observed in roach at the age of 3+. That one was significantly reduced in the age of 4+. The infection level of roach with L. intestinalis continued to decrease in the next age groups, going down to a minimum at the age of 7+. The roach wasn’t infected with this tapeworm at the age of 8+–10+. A significant reduction of the infection level in the roach in the age classes 4+ and older after the maximum at the age of 3+ was probably associated with parasite-induced mortality of the host during the growth of the age group 3+ to 4+. A standard body length of roach specimens infected with L. intestinalis at the age of 1+ and 2+ was greater than that of uninfected ones. In contrast, the standard body length of the roach specimens infected with this tapeworm was less than that of uninfected ones in subsequent age classes (3 + -6 +). Differences of standard body length between roach specimens infected with L. intestinalis and uninfected ones were statistically significant in the above-mentioned age groups (1 + 6 +). The effect of L. intestinalis plerocercoids on the linear growth of the roach in Chivyrkuysky Bay of the lake Baikal was manifested in an increase of body length of infected host specimens compared to uninfected ones in young age groups (1+ and 2+) and, vice versa, in one’s decrease in age groups 3+–6 +. We proposed to call this effect “reversive”.

Objective of research. The aim of the study was to explore the degree of contamination of pike and other fish species, plerosarcoidoma Diphyllobothrium latum in water bodies of the Baikal region. Materials and methods. In 2009-2014 was conducted parasitological study on infestation role of the D. latum plerocercoids of various species of fish. Just investigated 20 specimens of pike, 38 – burbot, 91 – perch and ruff 73 specimens in lakes of the North-Eastern part of Transbaikalia, located located in different districts of the Republic of Buryatia. The infection of fish with plerocercoids of D. latum were evaluated by extensiveness (EI), the abundance index (EI) and the intensity of infection (AI). Results and discussion. The pike infestation with plerocercoids of D. latum in lake. Goose in 2013-2014 decreased in 3 times compared with a maximum in 1973-1974 and was 0.8 % most Often, the D. latum plerocercoids are localized in the adipose tissue, the gonads, the wall of the swim bladder, liver, peritoneal epithelium, muscle, the wall of the stomach and the villagesince respectively 40,9 %; 13,8; 9,1; 9,1; 9,1; 4,5; 4,5; 4,5 and 4.5 % of cases. In Transbaikalia the fish parasitize three species of tapeworms, of which the epidemiological importance of the D. latum, D. dendriticum. D. ditremum in humans does not develop until the adult stage. In the region annually celebrate 150-450 cases of difillobotrioza in humans. In the basin of the Selenga river is-the reputed source of human infection by difillobotrioza are pike and perch, the infected with its good-Azerbaijani D. latum and the Baikal omul Coregonus migratorius infected with D. dendriticum. EI Baikal omul D. dendriticum is 62.3-100 %, and IO – 4,0-9,8 copies of This cestode is brought in the Selenga river from oz. The Baikal in the autumn spawning of Arctic Cisco. On owasco-FDI sample of human feces is impossible to distinguish the species D. latum and D. dendriticum. Probably in the Selenga region of Buryatia, there is a hotbed of difillobotrios caused by these two species of cestodes.

In certain regions of Siberia and Baikal area, the main causative agent of diphyllobothriasis of human and animals is gull-tipeworm Dibothriochephallus dendriticus. In last decade, there was heightened interest to the study of molecules secreted by helminth which can modulate the immune response of their mammal hosts, particularly human. Bioinformatic analysis of transcriptomes gives opportunity to obtain data on proteins synthetized in certain time point and find among them ones the most significant for immunological functions. The aim of our study was to carry out transcriptome analysis of adult D. dendriticus. Adult D. dendriticus were pulled from the gut of herring gull. Total RNA was extracted with TRIzol reagent. Bar-coding transcriptome libraries were created. Sequencing obtained libraries was carried out using high-performance sequencer Illumina NextSeq550. De-novo assembly of transcriptome was performed. Annotation of obtained transcripts was done with Blast2Go software. Annotation allowed to describe their classification in terms of biological processes, molecular functions, and cellular components. At the next step, we plan to use D. dendriticus, assembled and annotated with transcriptome of plerocercoids, to search genes, potentially coding proteins that have an immunomodulatory effect on their hosts and also for identification of the proteins in secretome of parasites.

The tapeworm Ligula interrupta of the genus Ligula (Digramma) (Cestoda: Pseudophyllidea) is a specific parasite of freshwater cyprinid fish; its plerocyrcoids are localized in the body cavity causing heavy parasitic pathology. With parasitosis, an important role in the regulation of the pathological process is assigned to the participants of the organism’s protective reactions, among which a special pool of immunocompetent cells – leukocytes – is distinguished. In the literature, there are single data on hemo- and immunopoiesis goldfish with digrammosis. In our work, new data were obtained on the leukocyte composition of the blood of goldfish Carassius auratus (Linnaeus, 1758), infected with Ligula interrupta in conditions of the native range (Shilen Lake and Cheremukhovoe Lake, Lake Baikal basin). All fish specimens caught with seine nets, both infested and noninfested with L. interrupta, were identical by the size and age composition (age +3…+5, body length 145–237 and 150–180 mm, respectively, weight 100–184 and 120–174 g). Hematological studies were carried out according to the Sbornik [2]. To quantify the individual types of leukocytes, the leukocyte profile, expressed in absolute terms, was calculated. Three groups of cells were revealed in the blood of all goldfish species: blast forms, granulocytes (neutrophils, pseudobasophils) and agranulocytes (lymphocytes, monocytes). The decrease in the blood of infected fish of the total number of leukocytes and their various types at all stages of development, the violation of the proliferation and differentiation of lymphoid and granulocytic elements in the studied organs, the formation of vacuolated and atypical cells, the absence of circulating basophils and eosinophils were established. It has been shown that in this parasitic system, partner relations are reduced to the launch of L. interrupta mechanisms that regulate the host's protective immunological processes by the type of inhibition of the acute inflammatory response and the development of mild chronic inflammation.

Triaenophorus crassus is the causative agent of muscular trienophorosis in fish, especially pathogenic for juvenile salmonids and coregonids. The purpose of this work was to analyze the infection of coregonids with T. crassus plerocercoids in the Chivyrkuisky Bay of the Lake Baikal and Tsipo-Tsipikanskiye (Bauntovskie) lakes (basin of the Lena River, Transbaikalia). Level of infection with plerocercoids T. crassus in coregonids from 1976 to 2013 in the Chivyrkuisky Bay of the Lake Baikal did not cause concern: the prevalence in the Baikal omul did not exceed 23.6%; intensity was no more than 6 specimens; the prevalence in the Baikal whitefish is up to 5.0%. At the same time, in 1954, in the Chivyrkuisky Bay, a higher level of infection of the Baikal omul was noted (the prevalence was 44.4%; the intensity was 1–9 specimens), which does not allow us to exclude a recurrence of this situation in the future. There was a sharply different situation in terms of infection of coregonids with T. crassus plerocercoids in two lakes of the Tsipo-Tsipikanskaya group: in the lake Bolshoye Kapilyushi, the prevalence of this cestoda is ten times higher than in the lake Baunt. It is likely that such contrasting levels of infection were associated with the difference in the location of the habitats of pike (the definitive host of T. crassus) and coregonids in these lakes: the coincidence in the lake Bolshoye Kapylyushi and divergence in the lake Baunt.