The effect of trematode parthenites on the individual fecundity of Bithynia troscheli (Prosobranchia: Bithyniidae)

Prevalence and distribution of trematodes hosted by Bithynia siamensis in Southern Thailand

This study aimed to investigate the occurrence of larval trematode infections in bithyniid snails across five provinces in southern Thailand. A total of 1,413 Bithynia siamensis snails were collected between October 2021 and October 2022 using handpicking and scooping methods. Among these, 844 were identified as B. s. siamensis and 569 as B. s. goniomphalos. The snail samples were examined for parasitic infections in the laboratory using shedding and crushing methods. Among the 27 sampling sites, snails from 6 sites were infected with various trematode species (infection rate: 4.95%, 70/1,413). Evaluation of the morphological and internal organ characteristics of the cercariae allowed for the categorization of the trematodes into five species of trematodes (belonging to four families). The identified species included Echinochasmus pelecani (family: Echinostomatidae), Echinostoma revolutum (family: Echinostomatidae), Haematoloechus similis (family: Haematoloechidae), Loxogenoides bicolor (family Lecithodendriidae), and Stictodora tridactyla (family: Heterophyidae), and the infection rates for these species were 3.26% (46/1,413), 0.35% (5/1,413), 0.42% (6/1,413), 0.78% (11/1,413), and 0.14% (2/1,413), respectively. The cercariae from the identified trematode species were studied for DNA analysis. The phylogenetic lineage reveals relationships among the species, confirming the morphological distinctions.

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

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04876-2.

Snail-borne parasitic diseases: an update on global epidemiological distribution, transmission interruption and control methods

Background

Snail-borne parasitic diseases, such as angiostrongyliasis, clonorchiasis, fascioliasis, fasciolopsiasis, opisthorchiasis, paragonimiasis and schistosomiasis, pose risks to human health and cause major socioeconomic problems in many tropical and sub-tropical countries. In this review we summarize the core roles of snails in the life cycles of the parasites they host, their clinical manifestations and disease distributions, as well as snail control methods.

Main body

Snails have four roles in the life cycles of the parasites they host: as an intermediate host infected by the first-stage larvae, as the only intermediate host infected by miracidia, as the first intermediate host that ingests the parasite eggs are ingested, and as the first intermediate host penetrated by miracidia with or without the second intermediate host being an aquatic animal. Snail-borne parasitic diseases target many organs, such as the lungs, liver, biliary tract, intestines, brain and kidneys, leading to overactive immune responses, cancers, organ failure, infertility and even death. Developing countries in Africa, Asia and Latin America have the highest incidences of these diseases, while some endemic parasites have developed into worldwide epidemics through the global spread of snails. Physical, chemical and biological methods have been introduced to control the host snail populations to prevent disease.

Conclusions

In this review, we summarize the roles of snails in the life cycles of the parasites they host, the worldwide distribution of parasite-transmitting snails, the epidemiology and pathogenesis of snail-transmitted parasitic diseases, and the existing snail control measures, which will contribute to further understanding the snail-parasite relationship and new strategies for controlling snail-borne parasitic diseases.

Electronic supplementary material

The online version of this article (10.1186/s40249-018-0414-7) contains supplementary material, which is available to authorized users.

Cercariae Opisthorchis felineus and Metorchis bilis from first intermediate hosts for the first time in basin of Chany lake (Novosibirsk region, Russia) is found

Objective of research: to perform the analysis of long-term (15 annum) dynamics of Bithyniidae snails infected by trematode parthenites from the Chany Lake, the biggest lake in the south of Western Siberia. Materials and methods: The Bithyniidae snails examined in the lake-river systems Chany Lake in 1994-2013 (in the middle reaches and in the estuary of the Kargat River) and in the Zolotye Rossypi Bay and the Malye Chany Lake. The Bithyniidae snails were collected from May to September (twice in any ten days) by hand from 4–6 plots of 0.25 m2 at a depth of 0.1–0.7 m. In total, 8,316 Bithynia troscheli (Paasch, 1842) and 766 В. tentaculata (L., 1758) were examined. Identification of parthenitae trematode was based on observation when mature cercariae were capable of leaving the shell of the host snail on their own. Results and discussion: In Bithyniidae snails, we found parthenites from trematodes from 12 families Cyathocotylidae Mühling, 1898 Poche, 1925; Prosthоgonimidae Luhe, 1909; Pleurogenetidae Looss, 1898; Lecithodendriidae Odhner, 1911; Microphallidae (Ward, 1901) Travassos, 1920; Plagiorchiidae Lühe, 1901 Echinostomatidae (Looss 1899) Dietz, 1909 Odhner 1910); Psilostomidae (Looss 1900) Odhner 1913; Notocotylidae Luhe, 1909; Monorchiidae Odhner, 1911; Cyclocoelidae Kossack, 1911 и Opisthorchidae (Lass, 1899) Braun, 1901. The prevalence of bithyniid snails infected by trematode parthenites varied from 1,6% to 24,1% in different years The double infection by trematode parthenites was found in 0,96% bithyniid snails from estuary of the Kargat River; 4,45% in the Malye Chany Lake, and 26,6%, in the Zolotye Rossypi Bay. The cercariae of Opisthorchidae family in four annum of the fifteen detected. The prevalence of bithyniid snails infected by trematode parthenites from Opisthorchis felineus (Rivolta, 1884) and Metorchis bilis (Braun, 1890) was observed in Chany Lake systems for the first time. Both species (O. felineus and M. bilis) of trematodes have danger to human health and causes very dangerous disease, opisthorchiasis and metorchiasis.