Metorchis Bilis Research Articles

Endoparasites of peritoneal organs and skeletal muscles of the European wildcat (Felis silvestris) in Germany

Abstract Background For several decades, the European wildcat (Felis silvestris) has gradually been returning to the forests of Germany, mainly in the central and southwestern regions. To increase the knowledge about this threatened species, the endoparasite status of dead found specimens from Germany was surveyed. Methods A total of 118 wildcats were examined for endoparasites in peritoneal organs and skeletal muscles. Owing to decomposition or incomplete carcasses, 104 gastrointestinal tracts (stomachs and intestines), 101 livers with gallbladders, 99 urinary bladders, as well as kidneys of 95 and skeletal muscles of 112 specimens were available for examination. All detected parasites were identified morphologically to genus or species level, followed by molecular examinations of one to ten specimens of each parasite species. Results Overall endoparasite prevalence in peritoneal organs was 99.0% (103/104). Among the 99.0% (103/104) infected gastrointestinal tracts, the most frequent species were Toxocara cati (95.2% [99/104]), Hydatigera kamiyai (84.6% [88/104]), Mesocestoides litteratus (69.2% [72/104]), Strongyloides spp. (58.7% [61/104]), Cylicospirura petrowi (37.5% [39/104]), Ancylostoma tubaeforme (31.7% [33/104]), Capillaria putorii (24.0% [25/104]), and Echinococcus multilocularis (18.3% [19/104]). In 77.8% (77/99) of the urinary bladders, Capillaria plica and/or Capillaria feliscati were detected. Moreover, the liver fluke Metorchis bilis occurred in 2.0% (2/101) of the livers, and roundworm larvae (presumably Toxocara spp.) were detected in 33.0% (37/112) of the muscle samples. Conclusions These results show a broad spectrum of endoparasite species infecting European wildcats in Germany. It might be assumed that some of the endoparasites could pose a risk to domestic cats (Felis catus) and humans through spillover events, or may be transmitted from domestic cats to the free-ranging population, posing a potential risk to wildcats. Graphical Abstract

TREMATODA AND CESTODA SPECIES IN CYPRINID FISH FROM SMALL LAKES OF THE KOSTANAY REGION

This study presents data on the epizootiological monitoring of parasitic diseases in fish from Kostanay region. It confirms the presence of previously identified permanent natural foci of opisthorchiasis in the southern districts, specifically in the Uly-Zhilanchik and Torgay rivers. Additionally, the research conducted in Zhangeldy and Amangeldy districts revealed the existence of biohelminths with both epizootiological and epidemiological significance. This study aimed to investigate the presence of parasites dangerous to humans and carnivores in cyprinid fish species. Specifically, it focused on identifying the second intermediate hosts for opisthorchiasis, metorchiasis, and ligulosis: ide (Leuciscus idus) and bream (Abramis brama). From 2021 to 2023 seven reservoirs of the Kostanay region were the monitoring objects of the parasitological situation: Verkhnetobolskoe reservoir, rivers: Torgay, Uly-Zhilanchik, Zhaldama, Tobol, Zhelkuar, Akkol Lake, where shellfish bitiniids, waterfowl and crustaceans live in large numbers, as the first intermediate host of pathogens Opisthorchis felineus (Metorchis bilis), Ligula imestinalis. Examination of eight ide (Leuciscus idus) specimens caught in the Uly Zhilanchik River revealed the presence of metacercariae of two parasitic trematodes: O.felineus and M.bilis, while the prevalence was 18.5% and 8.3%, and the infestation intensity was 1-3 and 2, respectively. In the Amangeldy region, metacercariae O. Felineus and plerocercoids Ligula imestinalis were found in two fish species: one individual of the ide species and two individuals of the bream species caught from the Torgai River. At the same time, the prevalence was 6.6% and 16.6%, and the infestation intensity was 2 and 1, respectively. Parasitic diseases of fish were not detected in the waters of Denisovsky and Zhitikarinsky districts. Based on Polymerase Chain Reaction (PCR) analyses conducted using specific primers at the National Center of Biotechnology LLP laboratory in Astana, Kazakhstan, two distinct types of opisthorchid parasites were identified in two ide (Leuciscus idus) specimens collected from Kostanay region. The species were confirmed to be Opisthorchis felineus and Methorchis bilis (PCR protocol dated April 24, 2023).

On the species composition of fish parasites in rivers and lakes in the south of Western Siberia

The fish from 11 lakes and 4 rivers of four regions of the south of Western Siberia (Novosibirsk, Tomsk, Kemerovo and Omsk regions), were examined from May to November 2015. A total of 817 specimens 14 fish species to five families: Coregonidae (1 species), Thymallidae (1), Cyprinidae (8), Lotidae (1), Percidae (3) were inspected for ectoparasites and endoparasites were infestation. In the present study taxonomic composition of ectoparasites includes representatives of four families of crustaceans (Lernaeopodidae, Lernaeidae, Argulidae and Ergasilidae) and leeches (Glossiphoniidae). Monogeneans were represented by three families: Dactylogyridae, Tetraonchidae and Diplozoidae. Cestodes of two families Ligulidae and Dilepididae were discovered. Fish infected with сestodes family Diphyllobothriidae were no found. The species composition of trematodes is the most diverse (7 genera to 4 families). Metacercariae of the families Diplostomatidae (genera Diplostomum , Posthodiplostomum , Tylodelphys ), Bucephalidae (genus Rhipidocotyle ), Prohemistomatidae (genus Paracoenogonimus ), and Opisthorchiidae (genus Metorchis and Opisthorchis ) were identified. Opisthorchis felineus , and Metorchis bilis , are two opisthorchiid species potentially perilous to human health, and domestic pets (cats, dogs) were found. Metacercariae of O. felineus , in all regions (Novosibirsk, Tomsk, Kemerovo and Omsk), in all surveyed rivers: Kiya, Tom, Irtysh and Ob were found. The opisthorchiid metacercariae potentially perilous to human health in three species (dace, ide, roach) out of eight studied (Cyprinidae) were found. The trematodes of the family Diplostomatidae were found in 8 fish species. The highest rates of infection were observed in roach and pike perch.

Opistorchids in the Novosibirsk urboecosystem

Opisthorchiasis in Novosibirsk and the Novosibirsk region is registered annually. Significant differences in the indicators of the epidemic process in Novosibirsk were noted in comparison with those in the Russian Federation, where the maximum and minimum average long-term incidence rate is 6–10 times lower than in Novosibirsk. The urban population share accounts for more than 75% of cases in the structure of the incidence of opisthorchiasis in the Novosibirsk region. The incidence rate of people with opisthorchiasis in different districts of the city varies from 85.0 per 100 thousand people to 170.3 in 2005–2015, an increase in the incidence rate is observed in most administrative districts and in the whole city. The opisthorchids infection rate of domestic carnivores is 15%. Cats are infested more often than dogs – 18.1 and 10.7%, respectively. In two districts of the city, Kirovsky and Sovetsky ones, the level of infection of domestic carnivores and the incidence of people significantly exceed those in other areas. In 6 fish species of the Cyprinidae family (Leuciscus idus, L. leuciscus, Rutilus rutilus, Abramis brama, Leucaspius delineatus, Carassius carassius), caught in urban and suburban water bodies, 3 opisthorchid species were found, namely: Opisthorchis felineus (Rivolta, 1884), Metorchis bilis (Braun, 1890), and M. xanthosomus (Creplin, 1846). The first two ones are of epidemic importance, while the last one is of epizootic significance. The total invasion prevalence of commercial ide by opisthorchid larvae in the Ob River was 71.8%, of which O. felineus metacercariae accounted for 69.1%. The overall infection level in small aboriginal fish in the small rivers Nizhnyaya Yeltsovka, Inya and Tula is 45.8, 55.3, and 22.2%, respectively. Thus, favorable environmental conditions have developed in Novosibirsk for transformation of the natural focus of opisthorchiasis into an anthropic one.

Freshwater gastropods as pathogens of natural focal invasions in the aquatic ecosystems of the Chernobyl exclusion zone

It has been established that 20 species (including two species complexes) of freshwater gastropods from 7 families live in water bodies on the territory of the PSRER, in which 51 species of trematodes from 21 families with a predominance of species of the Echinostomatidae family (10 species) parasitize at the parthenitis stage. The maximum number of trematode species was registered in the mollusks Lithoglyphus naticoides and Planorbarius corneus – 8 species of parasites with an infestation of 11.0 and 28.4 %, respectively. In the exclusion zone of the Chernobyl NPP, the circulation of natural focal helminthiasis caused by parasitization of trematodes Opisthorchiidae (Metorchis bilis, Pseudamphistomum truncatum, Opisthorchis felineus) identified in the studied animal species was established. For the mollusk Bithynia leachii, a high degree of infection (43.1 %) with the trematode O. felineus was noted.

Molecular genetic species definition of Opisthorchiidae-like cercariae from Bithyniidae snails of Chany Lake (South-Western Siberia, Russia).

The studies of opisthorchiids larval stages associated with Bithyniidae snails can provide important and the most reliable data for opisthorchiidoses foci characterization due to the low mobility of such opisthorchiid's host species as Bithyniidae snails. The foci of opisthorchiosis (caused by Opisthorchis felineus) and metorchiosis (caused by Metorchis bilis) are overlapping in the basins of the Ob and Irtysh Rivers. Thus, difficulties with determining the species of cercariae significantly reduce the accuracy of epidemiological conclusions regarding opisthorchiosis, which has a much higher medical significance. Moreover, M. bilis cercariae identification is complicated by the fact that the focus of metorchiosis caused by Metorchis xanthosomus (infecting fish-eating predatory birds) occurs on the same territory. In this study, we for the first time carried out the molecular genetic identification of West-Siberian opisthorchiid cercariae to verify morphological identification and confirmed O. felineus's main association with Bithynia troschelii snail and M. bilis'-with B. tentaculata snail. Thus, our study applied a two-stage approach: the morphological identification of any opisthorchiid-like cercariae in Bithynia snails and subsequent molecular genetic precise species determination of cercariae in the reduced samples.

The influence of ecological features of the Novosibirsk reservoir on its infection with Metorchis bilis

The West Siberian region is the focus of the spread of opisthorchiasis. The first intermediate hosts of these trematodes are pregill gastropods of the fam. Bithyniidae (Gray, 1857). Mollusks eat the eggs of these parasites, and after a cycle of asexual reproduction, opisthorchid larvae (cercariae) emerge from them, which swim in the water and penetrate into the bodies of fish through the skin. Danger for humans and carnivores is represented by fish of carp species (second intermediate hosts), but most often parasites of this fam. Opisthorchidae (Loose, 1899) occur in the ide (Leuciscus idus (Linnaeus, 1758)). The article presents data on the modern ichthyoparasitological state of the ide from the Novosibirsk reservoir and its abundance in the reservoir, on the places of mass accumulation of fish and mollusks in the reservoir, and describes the feeding habits of the studied fish. The relationship between the trophic preferences of this fish species and the indicators of its infection with opisthorchids is revealed: the ide, which feeds mainly on mollusks, lives in those parts of the reservoir where it can satisfy its needs, being in the zone of maximum risk of infection with trematode cercariae. The article explains the surge in infection of an ide from the reservoir with the trematode Methorchis bilis (Braun, 1890) in 2020. The hydrological regime of the reservoir, which is unfavorable for gastropod mollusks, and the presence of an alien species of gastropods Viviparus viviparus (Linnaeus, 1752) competing with bithyniids, as a rule, restrains the growth in abundance molluscs fam. Bithyniidae, which also affects the distribution of opisthorchiasis in fish, however, favorable conditions in 2020 allowed the population of mollusks to increase their numbers, which caused an increase in invasion rates in ide.

Bithyniid snails as hosts of Opisthorchiidae and Notocotylidae in the south of Western Siberia, Russia.

Opisthorchiasis and related infections are persistent and substantial public health burdens from eastern Europe to southeastern and northern Asia. Snails of the family Bithyniidae act as first intermediate hosts not only for the trematodes of the family Opisthorchiidae but also for those of the family Notocotylidae. There are certain morphological similarities between the aforementioned trematode cercariae. In order to find natural local foci of opisthorchiasis, which are established primarily according to the presence of infected bithyniid snails at the area under examination, it is crucial to correctly identify the rediae and cercariae of the trematodes. The aim of our investigation was to evaluate the role of bithyniid snails in the transmission of Opisthorchiidae and Notocotylidae in ecosystems in the south of Western Siberia. We have been studying the process of bithyniid snail dissemination in Western Siberia and examining their infection by trematodes from 1994 until now. A total of 16,213 bithyniid snails in 23 water bodies (in 28 localities) of four major basins situated in the Novosibirsk region were inspected for trematode infestation. Long-term research has been conducted in the Kargat river estuary and the Ob river floodplain for 15 and 25years, respectively. In both water bodies, the prevalence of notocotylid and opisthorchiid trematodes was positively correlated with the global land-ocean temperature index. Trematode parthenitae were identified if there were mature cercariae capable of leaving the shell of the host snail on their own. Identification to the species of opisthorchiid cercariae was verified using molecular genetic analysis methods targeting ITS2 locus. Opisthorchis felineus and Metorchis bilis, two opisthorchiid species that are potentially perilous to human health, were found in bithyniids in the Novosibirsk region. The mean prevalence of infection with notocotylid trematodes in bithyniid snails was higher than the corresponding prevalence of infection with opisthorchiid trematodes. The results of this study can be used to identify and predict natural foci of epidemiologically and/or epizootically dangerous diseases.

Metorchis bilis

This datasheet on Metorchis bilis covers Identity, Distribution, Hosts/Species Affected.

Systematic examination of the cardiopulmonary, urogenital, muscular and gastrointestinal parasites of the Eurasian otters (Lutra lutra) in Denmark, a protected species recovering from a dramatic decline

The Eurasian otter (Lutra lutra) is a protected species in Denmark and at present, the population is recovering due to conservation efforts. The Danish otters are mainly found in the continental part of Denmark (Jutland), but establishment in the main islands (Fyn and Zealand) has been observed. While there is a lack of systematic studies on the parasite fauna of otters in Denmark, this study aims to screen otters for their parasite fauna, especially those of zoonotic and/or veterinary importance. Thirty-three otter carcasses, road-killed (n=30), found dead (n=2) and shot (n=1), were collected between June 2013 and May 2014 and examined for cardiopulmonary, urogenital, gastrointestinal, and muscle helminths by post mortem examination. Faecal samples were analysed by modified concentration McMaster technique and direct immunofluorescence test for Giardia and Cryptosporidium. At least one parasite was found in 75.8% of animals. The parasite fauna included 13 species, consisting of five nematodes: Molineus patens (30.3%), Aonchotheca putorii (27.3%), Strongyloides sp. (24.2%), Physaloptera sp. (12.1%), Eucoleus aerophilus (10.0%); one cestode: Schistocephalus solidius (6.1%); four trematodes: Metorchis bilis (33.3%), Isthimiophora melis (15.2%), Cryptocotyle sp. (3.0%), Plagiorchis sp. (3.0%); one acanthocephalan: Acanthocephalus ranae (18.2%); and two protozoans: Giardia spp. (3.1%), and Eimeria spp. (3.1%). The study showed that otters carry parasites of zoonotic and veterinary importance. Many of these parasites can also infect native carnivores and birds, and the distribution of these parasites may be affected if the otter population continue to increase in Denmark.

Veterinary-sanitary expertise of the fish from the Shagalaly river

Fish completes the food chain of the water and is used an indicator of the water pollution. This article presents the results of biochemical, microbiological and parasitological studies of fish caught in the Shagalaly River. A total of 106 specimens of fish belonging to the Cyprinidae family were examined. As a result, it was established that there was no ammonia in the muscles of fish meat, the reaction to hydrogen sulfide was negative, the concentration of hydrogen ions in the studied samples were in the range of 6.6 - 6.7. The number of mesophilic aerobic and facultative anaerobic microorganisms was not observed at a cultivation cell of 1 × 105, which corresponds to the norm. Coliform bacteria was not found. When determining bacterial contamination for a reductase test, the samples were discolored after more than 3 hours, which indicates the absence of reductase. Metacercariae of the Opisthorchiidae family were found by the microscopy of muscles. The infection of ide by Opisthorchis felineus was 12.1%, Metorchis bilis - 6.09%, Metorchis xanthosomus - 10.9%, Pseudamphistomum truncatum - 2.4%. Pseudamphistomum truncatum was found in the muscles of the crucian carp, the infection rate was 29.1%. Molecular genetic analysis was carried out for the species differentiation of Opisthorchis felineus and Metorchis bilis metacercariae.

CYPRINID FISH INFECTION WITH METACERCARIAS OF TREMATODES UNDER ANTHROPOGENIC EFFECT

We presented parasitological studies of fish (Cyprinidae) in the Usman River within the Voronezhsky Biosphere Reserve. The infection of fish with metacercarias of trematodes in the river sections with various anthropogenic effect was assessed. We identified metacercarias of 6 species of trematodes: Opisthorchis felineus, Pseudamphistomum truncatum, Metorchis bilis, M. xanthosomus, Posthodiplostomum cuticola, and Paracoenogonimus ovatus. The highest occurrence and abundance of P. cuticola (95.4%, 36.4 sp.) and P. ovatus (56.9%, 8.8 sp.) was noted in the upper reaches of the River, in areas with high anthropogenic impact. An increased prevalence of infection was recorded for the group Opisthorchiidae (O. felineus, P. truncatum, and M. bilis) in areas within the Reserve with minimal anthropogenic impact. Infection rate of Opisthorchiidae metacercarias was 86.5% and 8.2 specimens in the middle and lower reaches of the River. At the same time, we noted a decrease in infection with P. cuticola (54.5%; 5.8 sp.) and P. ovatus (33.9%; 1.3 sp.). The degree of anthropogenic eutrophication of the Reservoir affects the development of different species of mollusks and the infection of fish with metacercarias. Metacercarias of trematodes can be used as indicators of water pollution in assessing anthropogenic effect on natural ecosystems.

THE PROBLEM OF BERDSKY BAY OF THE NOVOSIBIRSK RESERVOIR IN RELATION TO OPISTHORCHIDOSES

We studied the epidemic situation of opisthorchiasis in the population of Berdsk, and determined the level of infection of fish of the family Cyprinidae by larvae of opisthorchides in Berdsky Bay, as well as the abundance of the first intermediate host of the parasite, the mollusks of the family Bithyniidae in the water body. It is found that Berdsky Bay is generally unfavorable for opisthorchiasis. The incidence of opisthorchiasis in people in Berdsk was recorded annually; the average long-term incidence rate was 89.85 per 100 thousand of population with a minimum of 21.4 in 1991 and a maximum of 188.5 in 2002. The level of infection of cyprinid fish with metacercarias of opisthorchides is quite high (33.3%).The epidemic danger is posed by fish infected with larvae of Opisthorchis felineus (the prevalence 31.7%) and Metorchis bilis (the prevalence 3.3%). The ide, dace and verkhovka represent a high potential danger in infecting the population with opisthorchiasis and are indicators of the adverse situation with the reservoir as regards the invasion. In the water area of Berdsky Bay, we identified new actively functioning foci of opisthorchis invasion located in the Lebedevskaya and Elbanskaya streams, as well as in the mouth of the Sukhaya River where not only infected fish were recorded, but also the number of the first intermediate host of opisthorchides, the mollusks of the family Bithyniidae (Bithynia troscheli and B. tentaculata), is quite high.

Iberian Distribution of the Freshwater Snail Genus Bithynia Leach, 1818 (Mollusca: Truncatelloidea), Vector of Opisthorchiasis and Metorchiasis.

Opisthorchis felineus and Metorchis bilis are trematodes that cause opisthorchiasis and metorchiasis, respectively. The freshwater snails Bithynia hispanica and B. tentaculata are the respective intermediate hosts for these parasites in the Iberian Peninsula, where both parasites are present. To study the distribution of these snail species, an exhaustive literature review and revision of museum collections was performed. A total of 370 localities were compiled and mapped. B. tentaculata were found throughout the Iberian Peninsula, both in Spain and Portugal, while B. hispanica was found only in the Mediterranean coast of Spain. Knowing the distribution of the Bithynia species found in the Iberian Peninsula is highlighted in terms of public health, as the presence of the snail is related to the presence of the disease and can be used as a tool to face future outbreaks.

Seasonal assessment of invasion of yard dogs socially dangerous helminths in region of the North Caucasus

Authors studied the seasonal invasion of yard dogs by socially dangerous bio- and geohelminths on the territory of the Republic of Kabardino-Balkaria. In the Republic of Kabardino-Balkaria, during all seasons of the year, domestic dogs are the source of 9 zoonotic species of helminths, such as Metorchis bilis, Echinococcus granulosus, Dipylidium caninum, Mesocestoides lineatus, Toxocara canis, Ancylostoma caninum, Dirofilaria repens, Dirofilaria imitis и Trichinella spiralis for a person. Quantitative indicators of the extent of invasion caused by socially dangerous helminths of the species Metorchis bilis, Echinococcus granulosus, Dipylidium caninum, Mesocestoides lineatus, Toxocara canis, Ancylostoma caninum, Dirofilaria repens, Dirofilaria imitis и Trichinella spiralis ranging from 13.33% to 60.00%. In autumn, in domestic dogs, socially dangerous helminths of the species Metorchis bilis, Echinococcus granulosus, Dipylidium caninum, Mesocestoides lineatus, Toxocara canis, Ancylostoma caninum, Dirofilaria repens, Dirofilaria imitis и Trichinella spiralis were recorded with large amounts ranging from 6.67% to 40.00%. It was established that in populations of yard dogs, the most frequently recorded species of socially dangerous helminths of zoonotic etiology in all seasons were Echinococcus granulosus, Toxocara canis, Ancylostoma caninum.

LOYMOPOTENTIAL OF TREMATODIASES FOCI AND THE RISK OF INFESTATION FOR THE POPULATION IN THE BELAYA RIVER ECOSYSTEM

Loymopotential of natural foci of opisthorchiasis, metorchiasis (Metorchis bilis) and pseudamphistomiasis determine risk of infestation for the population with these trematodiases. There is a focal system of combined natural foci of opisthorchiasis – metorchiasis (M. bilis) – pseudamphistomiasis in floodplain-river ecosystem of the Belaya River in the carry-over area of pseudamphistomiasis causative agent which enters the river course with a bleak population. There is a stable risk of infestation for the population with the agents of these parasites through when eating bleak (age group of fish from one to three years old and elder) caught in the river course (the combined area of the carry-over of the opisthorchiasis, metorchiasis (M. bilis) and pseudamphistomiasis causative agents).

Description of a new species, Cryptocotyle lata sp. nov., and discussion of the phylogenetic relationships in Opisthorchioidea

Adult Cryptocotyle lata sp. nov. worms were obtained from experimental studies. In the Russian southern Far East, the life cycle of this parasite is carried out using freshwater snails (Boreoelona ussuriensis), freshwater fish, and birds as the first intermediate, second intermediate, and definitive hosts, respectively. The morphological indices of C. lata sp. nov. are closest to Cryptocotyle concava; however, these two species differ in terms of their sizes of body, oral and ventral suckers, eggs, and the shape of their testes and ovaries. Analysis of the life cycles of the Cryptocotyle representatives suggested that C. concava were at least two cryptic species, one of which circulates using brackish water Hydrobia snails, and the other using freshwater Amnicola snails as the first intermediate hosts. Molecular data (i.e., the 28S gene and the second internal transcribed spacer (ITS2) of rDNA) were used to analyze the phylogenetic relationships of C. lata sp. nov. and other representatives of Opisthorchioidea. The long repeats and secondary structure of the ITS1 region were studied. Representatives of the Opisthorchiidae and several species from Heterophyidae (including the genus Cryptocotyle) were found to have molecular features that suggested that these species belonged to Opisthorchiidae. At the same time, the genetic relatedness of worms, which are united in common clusters on phylogenetic trees, is consistent with the use of the first intermediate hosts from different taxonomic groups in their life cycles; namely, snails of the Truncatelloidea are hosts of trematodes from a cluster with Opisthorchiidae and a number species of the family Heterophyidae, while snails of the Cerithioidea are hosts of worms from a cluster that includes only the Heterophyidae. In addition, the results of genetic studies indicate that Clonorchis sinensis, Metorchis ussuriensis, Metorchis bilis, Metorchis xanthosomus, and Metorchis orientalis should be included in the genus Opisthorchis.

CHARACTERISTIC OF COMBINED NATURAL FOCI OF DISTOMIASIS IN THE ECOSYSTEM OF THE LOWER STREAM VAGAJ RIVER (TYUMEN REGION)

In the ecosystem of the lower stream of the Vagaj river is established the presence of natural foci of opisthorchiasis, metorchisiases (Metorchis bilis, Metorchis xanthoso-mus), rhipidocotyliasis and paracoenogonimiasis forming 10 types of combined foci. The combination of natural foci of trematodes in the presence of common hosts of the pathogen in nine types of combined foci is predetermined by the formation of parasitocenosis between hemypopulations of the parasite and populations of hosts, and in one combined focus – parasitocenosis in parasitic systems. At the same time, these parasitic systems of agents form infestation-infestation population-combined and system-combined foci. 6 sites of the river bed and 12 floodplain reservoirs have been searched for the presence of mollusks – the first intermediate hosts of trema-todes. Malacofauna of the reservoirs is represented by 10 species of mollusks. Their number is extremely variable and varies from the complete absence of some species to 15–20 specimens/m2Limnaea stagnalis and Anodonta cygnea. 988 youngs-of-the year, 219 of one-year old, 118 – two years old and 14 – three years old fishes of the family Cyprinidae, caught at 14 biotopes, have been investigated by the compressor method. Youngs-of-the year and yearlings were compressed and viewed completely. The study of the fishes showed their infestation by metacercariae Opisthorchis felin-eus, Metorchis bilis, Metorchis xanthosomus, Paracoenogonimus ovatus, and Rhipido-cotyle companula.

FISH INVASION BY OPISTHORCHID FLUKES IN THE WATERPOTS OF THE CITY OF NOVOSIBIRSK

The article presents data on the contamination of carp family fish with opisthorchid metacercariae and on the basis of this study, local foci of opisthorchidosis in reservoirs within the city of Novosibirsk were identified. Fishes for research were caught in the Nizhnyaya Yeltsovka and Inya rivers within the city of Novosibirsk. Fish studies were carried out by the compressor method. A total of 121 specimens of five species were investigated: ide, roach, dace, bream, verkhovka. Three types of opisthorchid metacercaria are found: Opisthorchis felineus, Metorchis bilis, and M. xanthosomus. The first two species have an epidemic significance, the latter – epizootic one. To assess the infection of fish, indicators of extensiveness and intensity of invasion, as well as an abundance index, were used.The results of studies showed that the level of infection of carp fish with larval forms of opisthorchids is 48.8% in total, while infection with metacercariae is: O. felineus 19.8%, M. bilis is 27.3% and M. hantomomus is 4.1%. In Lower Yeltsovka, the infection rate was 45.8%, in Ina – 55.3%. Earlier, our studies in the Lower Yeltsovka river detected mollusks-bitiniids, the first intermediate hosts of opisthorchids infected with their partins. Since the presence of the first and second intermediate, as well as definitive (human) hosts, is recorded at this point, the presence of a local focus in Lower Eletsovka can be considered indisputable. In Ina, the presence of a local focus is highly likely; for its final proof, it is necessary to detect opisthorchid-infected mollusks of this parthenites of Bithyniidae family.

Opisthorchis felineus and Metorchis bilis Metacercariae in Cyprinid Fish Leuciscus idus in Nura-Sarysu River, Kazakhstan.

Aim of the present study was to provide presence of opisthorchiid metacercariae in cyprinid fish Leuciscus idus in Nura-Sarysu river, Kazakhstan. Infection rate of the ides by the metacercariae was 42%. The metacercariae, similar morphologically to those of the liver flukes, were found: elliptical in shape, 0.19–0.25×0.15–0.22 mm, oral and ventral suckers nearly equal size, and excretory bladder O-shape with black content, occupying posterior part of the body. The metacercariae were divided into 2 groups with differences in size and thickness of cyst wall. Adult flukes were recovered from the Syrian hamsters infected with the opisthorch metacercariae and identified with morphological characters to Opisthorchis felineus and Metorchis bilis. DNA sequences of ITS1, ITS2, and cox1 supported the taxonomic assignment.