Effects of Environmental Factors and Infecting Trematodes on the Size and Inorganic Elements of Bithynia siamensis goniomphalos Snails in Northeast Thailand

Infection with the foodborne trematode, Opisthorchis viverrini, is a major public health issue in southeast Asia. The freshwater snail, Bithynia siamensis goniomphalos, is an intermediate host of O. viverrini and other trematode species. Understanding the effects of environmental conditions and infecting trematodes on B.s. goniomphalos snails is thus crucial for the potential influences on trematode transmission. This study measured environmental variables of water and soil properties, and analyzed B.s. goniomphalos snails for their trematode infection, snail shell length, and inorganic elemental concentration, from 30 localities in northeast Thailand. The results showed that prevalence of trematode infection in B.s. goniomphalos was 3.82%. Nine types of trematode cercariae were identified, with virgulate type 1 as the most common (1.23%). Opisthorchis viverrini-infected snails were mostly found in low-humic gley soils in Sakon Nakhon Province, and were associated with water dissolved oxygen and soil pH. Compared with uninfected snails, larger sizes were observed in virgulate type 1 and pleurolophocerca-infected snails, whereas hypercalcification was noticed in virgulate type 1, virgulate type 3, and pleurolophocerca-infected snails. Infected snails were more sensitive toward environmental conditions, possibly because of the dynamic parasitic processes between trematodes and hosts. Among the environmental factors, soil texture (i.e., sand, silt, and clay compositions) exhibited more significant correlations with B.s. goniomphalos shell characteristics regardless of the trematode infection types. The findings of this study underscore the need to consider the effects of environmental conditions and trematode species-specific pathogenic processes for a more effective and sustainable parasitic control and prevention effort.

Трематоды (Trematoda, Plathelminthes) азиатского бурундука (Tamias sibiricus) Магаданской области.

Data on trematodes (Trematoda) of the Siberian Cipmunk (Tamias sibiricus) in Magadan Oblast are presented. Four trematode species of the two families (Plagiorchiidae Lühe, 1901 (Plagiorchis vespertilionis (Müller, 1780); Pl. elegans (Rudolphi, 1802), Pl. eutamiatis (Schulz, 1932), and Brachylaimidae Goyeux et Folay, 1930 (Brachylaima recurva (Dujardin, 1845)) are identified. An illustrated description of all the four species of trematodes, first noted in the Chipmunk in the North-East of Russia, is given.

Rare inventory of trematode diversity in a protected natural reserve

In the face of ongoing habitat degradation and the biodiversity crisis, natural reserves are important refuges for wildlife. Since most free-living organisms serve as hosts to parasites, the diverse communities in protected areas can be expected to provide suitable habitats for a species-rich parasite fauna. However, to date, assessments of parasite diversity in protected nature reserves are rare. To expand our knowledge of parasite communities in natural habitats, we examined 1994 molluscs belonging to 15 species for trematode infections in a central European natural reserve. The parasitological examination revealed an overall prevalence of 17.3% and a total species richness of 40 trematode species. However, the parasite diversity and prevalence did not differ markedly from trematode communities in non-protected environments, which might be partly explained by a dilution effect caused by a high number of non-host organisms in our study system. The proportion of complex and long life cycles of parasites in the present study is high, indicating complex biotic interactions. We conclude that life cycle complexity, in addition to parasite diversity and trematode species richness, can provide valuable information on ecosystem health and should therefore be considered in future studies.

Establishing the role of amphibians (Anura) in the prophylaxis of helminths specific to domestic, wild and pet animals

This work is based on helminthological data of amphibians, collected since 2013 until 2020, in the Republic of Moldova. The investigations on anura amphibians were conducted in the laboratory of Parazitology and Helminthology of the Institute of Zoology. One of the most common parasitic diseases in ruminants is fasciolosis, caused by the trematode Fasciola hepatica species. The results of parasitological research showed that adult cattle were infected with fascioles in 66.4% of cases, and young cattle - in 46.1% of cases. This is largely due to the grazing of animals of different species and ages in limited areas.The presence of the trematode species Haplometra cylindracea was established in 78% of cases in the amphibians in the Ranidae and Bufonidae families (Rana ridibunda, Rana lessonae, Rana temporaria, Bufo viridis). The results of laboratory helminthological investigations have shown that the relationships between the Fasciola hepatica miracidium and the Haplometra cylindracea miracidium are antagonistic. Amphibians of the Ranidae and Bufonidae families (Rana ridibunda, Rana lessonae, Rana temporaria, Bufo viridis) infested with Haplometra cylindracea tremateda may play an important role in the prophylaxis of fasciolosis.

Long-term dynamics of trematode infections in common birds that use farmlands as their feeding habitats

Background The biodiversity of farmland habitats is witnessing unprecedented change, mostly in declines and simplification of assemblages that were established during centuries of the use of traditional agricultural techniques. In Central Europe, conspicuous changes are evident in populations of common farmland birds, in strong contrast to forest birds in the same region. However, there is a lack of information on longitudinal changes in trematodes that are associated with common farmland birds, despite the fact that diversity of trematodes is directly linked to the preservation of long-established food webs and habitat use adaptations of their hosts. Methods We analyzed the population trends of trematodes for the period 1963–2020 in six bird species that use Central European farmlands as their predominant feeding habitats. Namely, we examined Falco tinnunculus, Vanellus vanellus, winter populations of Buteo buteo, Ciconia ciconia, extravilan population of Pica pica, and Asio otus, all originating from the Czech Republic. Results We observed dramatic population losses of all trematode species in C. ciconia and V. vanellus; the changes were less prominent in the other examined hosts. Importantly, the declines in prevalence and intensity of infection affected all previously dominant species. These included Tylodelphys excavata and Chaunocephalus ferox in C. ciconia, Lyperosomum petiolatum in P. pica, Strigea strigis in A. otus, Neodiplostomum attenuatum and Strigea falconis in B. buteo (χ2 test P < 0.001 each), and Echinoparyphium agnatum and Uvitellina adelpha in V. vanellus (completely absent in 2011–2000). In contrast, the frequency and spectrum of isolated records of trematode species did not change to any large extent except those in V. vanellus. Conclusions The analysis of six unrelated common bird species that use farmlands as their feeding habitats revealed a previously unreported collapse of previously dominant trematode species. The previously dominant trematode species declined in terms of both prevalence and intensity of infection. The causes of the observed declines are unclear; of note is, however, that some of the broadly used agrochemicals, such as azole fungicides, are well known for their antihelminthic activity. Further research is needed to provide direct evidence for effects of field-realistic concentrations of azole fungicides on the survival and fitness of trematodes. Graphical abstract

Helminths of domestic and wild chicken birds (Aves: Galliformes) of Uzbekistan

The purpose of the research is studying existing fauna and ecology of Galliform helminths in biogeocenoses of Uzbekistan.Materials and methods. Parasitic worms were collected from chicken-like birds of the terrestrial cenoses of Karakalpakstan and North-eastern Uzbekistan. Birds were studied in all seasons of 2018–2020. Wild birds – Himalayan hen, keklik, grey partridge, quail and pheasant, were hunted by local hunters during hunting seasons, while domestic birds - chickens, turkeys and guinea fowls were uncovered from different types of poultry farms. The study of birds was carried out by well-known methods. It was examined 913 wild and 755 domestic chicken-like animals. The detected cestodes and trematodes were fixed in 70% alcohol, and the nematodes were fixed in Barbagallo liquid. The determination of helminth species was carried out according to the well-known guidelines of domestic and foreign authors.Results and discussion. We found that helminthoses were widespread among representatives of Galliformes in Uzbekistan. Total helminth infections in domestic and wild Galliformes were 50.5%. In infected birds, 44 helminth species were identified, among which 10 species were cestodes, 12 species were trematodes and 22 species were nematodes. Helminth species diversity was the most extensive in the domestic chicken (36 species), turkey (21), and partridge (20). For the first time for the helminth fauna in Galliformes in Uzbekistan, we identified 3 trematode species – Brachylaema fuscatus, Collyriclum faba and Echinostoma miyagawai, and 10 nematode species of the genera Capillaria, Aonchotheca, Ascaridia, Heterakis, Dispharynx, Streptocara, Tetrameres, Diplotriaena and Ornithofilaria.

The Ponto-Caspian parasite Plagioporus cf. skrjabini reaches the River Rhine system in Central Europe: higher infestation in the native than in the introduced Danubian form of the gastropod Theodoxus fluviatilis

The introduction of non-indigenous organisms in new areas in the context of host-parasite interactions is still poorly understood. This study aimed at a parasitological and histopathological comparison of two phylogenetically distinct forms of the freshwater snail Theodoxus fluviatilis in the River Rhine system: the native Northern-European form, which showed a decline for unknown reasons and is nowadays extinct in the River Rhine, and the non-indigenous Danubian form, which was introduced via the Main–Danube canal. We histopathologically examined populations of Northern-European T. fluviatilis from three smaller rivers of the Rhine system and of Danubian T. fluviatilis from the River Rhine, after confirming the phylogenetic background of the respective population genetically. Results showed differences in the prevalence of trematodes and histopathologic organic alterations between the two snail forms. Both were infected with an opecoelid trematode Plagioporus cf. skrjabini, whereby its prevalence was significantly higher in the Northern-European than in the Danubian form. The parasitic trematode is, to our knowledge, a new trematode species in the River Rhine system, presumably co-introduced through the invasion of its second intermediate and final hosts, i.e. Ponto-Caspian amphipods and gobies. Its impact on native populations of Northern-European T. fluviatilis needs to be subject of future studies.

Chronic Wasting Due to Liver and Rumen Flukes in Sheep

Grazing sheep and goats are constantly exposed to helminth infections in many parts of the world, including several trematode species that causes a range of clinical diseases. The clinical picture of flukes is dependent upon the organs in which they develop and the tissues they damage within the respective organs. Accordingly, infections with the common liver fluke Fasciola hepatica, which, as juvenile worm migrates through the liver parenchyma for several weeks, may be associated with hepatic disorders such as impairment of carbohydrate, protein and fat metabolism, followed by chronic wasting. In contrast, the lancet fluke Dicrocoelium dendriticum, which does not exhibit tissue migration and thus does not lead to major tissue damage and bleeding, also does not lead to significant clinical symptoms. Rumen flukes such as Cotylophoron daubneyi cause catarrhal inflammation during their migration through the intestinal and abomasal epithelium during its juvenile stages. Depending on the infection intensity this may result in a range of clinical symptoms including diarrhoea, inappetence or emaciation. In this review, we aim to provide an update on the current knowledge on flukes particularly concerning the clinical relevance of the most important fluke species in sheep.

The current state and specifics of taxonomic structure of trematodes of freshwater molluscs in the Ukrainian Polissia

The paper presents results on the analysis of the taxonomic structure of the trematode fauna of the Ukrainian Polissia. It was found that the trematode fauna of freshwater molluscs in the Ukrainian Polissia is represented by 62 species. We supplemented the species composition of larvae of trematodes in the region with 23 species, 13 of which were first recorded in Ukraine. The results showed that the number of trematode species the definitive hosts of which are fishes have decreased. According to the obtained data, the most abundant trematode species of freshwater molluscs in the Ukrainian Polissia are those of the families Echinostomatidae, Plagiorchiidae, Diplostomidae, and Notocotylidae. The combined analysis of literature and original data revealed that in the basis of the regional trematode fauna of molluscs are species of the families Echinostomatidae (13 species) and Plagiorchiidae (10 species), which make up almost one-third of the total number of trematode larvae detected. A quite large portion of larvae belong to species of the families Notocotylidae (8 species), Strigeidae (7 species), Diplostomidae (5 species), and Haematolechidae (5 species). Most families (Diplodiscidae, Opisthorchiidae, Leucochloridiomorphidae, Prostogonimidae, Cathaemasiidae, Cyclocoelidae, Prohemistomatidae, and others) are represented only by 1–2 species. In freshwater molluscs of the studied region, we have found only 38 % of trematode species recorded in definitive hosts. Species found in vertebrate animals of the region potentially can also occur in intermediate hosts, but most of these species parasitize in birds that could be infected in other areas. When comparing the taxonomic structure of the trematode fauna of the Polissia with other well-studied regions of Ukraine (Northern Pryazovia and Crimea), some specifics were noted between them. In particular, it was found that the most abundant trematode species in the region as well as in the whole of Ukraine are those of the families Echinostomatidae, Plagiorchiidae, Diplostomidae, Notocotylidae, and Strigeidae. The obtained data allow considering that the trematode fauna of freshwater gastropods of the Ukrainian Polissia is an integral part of the Central European fauna of trematodes.