Opisthorchis felineus or Siberian liver fluke is a trematode parasite (Opisthorchiidae) that infects the hepato-biliary system of humans and other mammals. Despite its public health significance, this wide-spread Eurasian species is one of the most poorly studied human liver flukes and nothing is known about its population genetic structure and demographic history. In this paper, we attempt to fill this gap for the first time and to explore the genetic diversity in O. felineus populations from Eastern Europe (Ukraine, European part of Russia), Northern Asia (Siberia) and Central Asia (Northern Kazakhstan). Analysis of marker DNA fragments from O. felineus mitochondrial cytochrome c oxidase subunit 1 and 3 (cox1, cox3) and nuclear rDNA internal transcribed spacer 1 (ITS1) sequences revealed that genetic diversity is very low across the large geographic range of this species. Microevolutionary processes in populations of trematodes may well be influenced by their peculiar biology. Nevertheless, we suggest that lack of population genetics structure observed in O. felineus can be primarily explained by the Pleistocene glacial events and subsequent sudden population growth from a very limited group of founders. Rapid range expansion of O. felineus through Asian and European territories after severe bottleneck points to a high dispersal potential of this trematode species.

The research aimed to determine the peculiarities of the formation of the parasitic system in herbivorous fish in the aquaculture of the North-Eastern and Eastern regions of Ukraine. In fish farms of the North-Eastern and Eastern regions of Ukraine, 26 species of parasites were found in herbivorous fish: 19 species in the silver carp (11 — protozoa, 1 — monogeneans, 4 — trematodes, 3 — parasitic crustaceans); 18 species in the grass carp (6 — protozoa, 1 — monogeneans, 4 — trematodes, 4 — cestodes, 3 — parasitic crustaceans); and 20 species in the bighead carp (10 — protozoa, 1 — monogeneans, 4 — trematodes, 2 — cestodes, 3 — parasitic crustaceans). 11 species (42.3%) of registered parasites were invasive; 18 species (69.2%) of the detected herbivorous fish’s parasites develop directly and 8 (30.8%) — with the participation of definitive and intermediate hosts; the fish is an additional (second intermediate) host in the life cycle of 6 species (23.1%) of parasites. Outbreaks of diseases caused by parasitic protozoa from the genera Myxobolus, Cryptobia, Chilodonella, and Ichthyophthirius have been reported in both fingerlings and two-year-olds. The protozoa from the genera Ichthyobodo, Trichodina, and Trichodinella were registered en masse only in fingerlings. Pathogens from the genus Dactylogyrus were more often registered among three-year-old silver and bighead carps. Metacercariae of Ichthyocotylurus variegatus were found en masse in fingerlings of the grass carp. Posthodiplostomum cuticola larvae in unfavorable farms were found with a high level of prevalence in fish of different age groups. Thong plerocercoids were more commonly recorded in two-year-old silver and bighead carps and fingerlings of the grass carp. The highest level of cestode infection with Bothriocephalus acheilognathi was recorded in fingerlings of the grass carp. Parasitic crustaceans Sinergasilus lieni with a high level of prevalence were registered in two-year-old and three-year-old fish. Crustaceans Lernaea cyprinacea massively affected two-year-old and three-year-old fish. Pathogens from the genera Trichodina, Cryptobia, and Chilodonella, and Dactylogyrus hypophthalmichthys, Posthodiplostomum cuticola, and Sinergasilus lieni were of the greatest epizootic significance for the silver carp; for the bighead carp — from the genus Myxobolus, (especially M. pavlovskii), Chilodonella piscicola, Ichthyophthirius multifiliis, Dactylogyrus aristichthys, Posthodiplostomum cuticola, Diplostomum spathaceum, Digramma interrupta, and Sinergasilus lieni; for the grass carp — Bothriocephalus acheilognathi, Ichthyocotylurus variegatus, Ligula intestinalis, Sinergasilus major, Lernaea cyprinacea, Ichthyobodo necator, and Ichthyophthirius multifiliis

The goal of the work was to study of acute and subacute toxicity parameters of “Rybokhin” biological product (AI – chloroquine refer to derivatives 4-aminohinolines) on the model of carp. This drug is effective in the treatment of diseases caused by parasitic Protozoa and Monogenea. Carp scales of two years old were used in experiments. To determine acute toxicity, the fish were prescribed with chloroquine (by AI) in doses of 100; 200; 300; 400; 500; 600; 800; 1000 mg/kg of live weight. Two experimental and control fish groups of 30 individuals each were formed to determine subacute toxicity of “Rybokhin”. Experimental groups of fish were prescribed with “Rybokhin” in a dose (by AI) of 50 mg/kg and 10 mg/kg for two consecutive days. Blood samples were collected from six fish species from each group for clinical and biochemical indicators after 48 hours, 7, 14, 21 and 28 days. The hemoglobin content, number of red blood cells and leukocytes blood were determined. The intensity of peroxide oxidation of lipids (PОL), catalase activity, level of total antioxidant capacity (TAC), total proteins, albumin, globulins and glucose, circulating immune complexes (CІC) and seromucoids concentration, level of enzymatic activity: aspartate transaminase (АSТ), alanine transaminase (АLТ), ά-amylase blood plasma were determined. According to the research results, indicators of acute toxicity for carp were determined, namely LD50 of chloroquine is 528.66 ± 68.01 mg/kg; LD16 – 224.512 mg/kg; LD84 – 832.81 mg/kg; LD100 – 984.89 mg/kg, which indicate that the drug is low-toxic to fish (belongs to the fourth group of toxicity). When administrating of 50.0 mg/kg of “Rybokhin” (by AI) twice a day, the most expressed metabolic changes in fish body were observed on 21 day after its last administration. Thus, the drug’s toxic impact is in proteinogram alteration, transamination processes and in decreasing of fish immune reactivity. It points to the prevalence of catalytic processes over anabolic. Metabolic alterations are obviously directed to the activation of detoxication processes with increased energy use in fish body after getting of higher dosage of the product. So, on 28 day of experiment, the major part of studied parameters retrieved to control level. It was found that when the product was administrated twice a day in the dosage 10.0 mg/kg (by AI), which is used for treatment of parasitic diseases, no reliable changes of clinical and biochemical indices were detected in fish blood during the experiment.

Yevtushenko, A. V. (2019). Effectiveness of the drug the «Ribontel» for the treatments against trematode parasites infecting the fish. Veterinary science, technologies of animal husbandry and nature management, 3, 110-116.

The goal of the work was to study of acute and sub-acute toxicity parameters of ‘Rybozuril’ biological product (AI — diclazuril) on the model of carp. This drug is effective in the treatment of diseases caused by parasitic Eimeriidae. Carp scales of two years old were used in experiments. To determine acute toxicity, the fish were prescribed with diclazuril in doses of 1 g/kg, 5, 10, and 15 g/kg of live weight. Two experimental and control fish groups of 30 individuals each were formed to determine sub-acute toxicity of ‘Rybozuril’. Experimental groups of fish were prescribed with ‘Rybozuril’ in a dose (by AI) of 50 and 10 mg/kg for two consecutive days. Blood samples were collected from six fish from each group for clinical and biochemical indicators after 2, 7, 14, 21, and 28 days. The hemoglobin content, number of red blood cells and leukocytes blood was determined. The intensity of peroxide oxidation of lipids (PОL), catalase activity, level of total antioxidant capacity (TAC), total proteins, albumin, globulins and glucose, circulating immune complexes (CІC) and seromucoids concentration, level of enzymatic activity: aspartate transaminase (АSТ), alanine transaminase (АLТ), α-amylase blood plasma were determined. The acute toxicity of diclazuril for carp was estimated, LD50 is more than 15,000 mg/kg of live weight, the toxicity of diclazuril can be classified as undifferentiated and, in terms of toxicity, it can be classified as hazard class IV. Two administrations of the drug ‘Rybozuril’ in a daily dose of 50.0 mg/kg of live weight, the maximum expression of metabolic changes in fish was detected from the initial terms of the studies and up to day 21. According to the results the toxic effect of the drug in fish was estimated, which did not influence to a number of indicators. The drug in such dose was shown immunosuppression and membrane-toxic effects in fish. Two-time administration of the ‘Rybozuril’ drug in a daily dose of 10.0 mg/kg body weight leads to metabolic alterations in fish due to the activation of detoxification processes and lipoperoxidation maintenance in cell membranes at the physiological level. At the end of the experiment the toxic effect of ‘Rybozuril’ in fish characterized by stable parameters in comparing to the control group.