Main Intermediate Host Research Articles

Risk of invasion and disease transmission by the Australasian freshwater snail Orientogalba viridis (Lymnaeidae): a field and experimental study

BackgroundBiological invasions pose risks to the normal functioning of ecosystems by altering the structure and composition of several communities. Molluscs stand out as an extensively studied group given their long history of introduction by either natural or anthropogenic dispersal events. An alien population of the lymnaeid species Orientogalba viridis was first sighted in 2009 in southern Spain. In its native range (Australasian), this species is one of the main intermediate hosts of Fasciola hepatica, a major worldwide trematode parasite largely affecting humans, domestic animals and wildlife.MethodsWe collected field populations of O. viridis from its native (Malaysia) and invaded (Spain) ranges. We performed detailed morphoanatomical drawings of the species and screened for natural infection of parasites. Individuals were molecularly characterized using ITS2 for comparison with existing sequences in a fine phylogeography study. We founded experimental populations at two different conditions (tropical, 26 °C and temperate, 21 °C) to study the life-history traits of exposed and non-exposed individuals to different F. hepatica isolates.ResultsWe found a 9% natural prevalence of trematode infection (98% similarity with a sequence of Hypoderaeum conoideum [Echinostomatidae]) in the Spanish field population. The haplotypes of O. viridis found in our study from Spain clustered with Australian haplotypes. Experimental infection with F. hepatica was successful in both experimental conditions but higher in tropical (87% prevalence) than in temperate (73%). Overall lifespan, however, was higher in temperate conditions (mean 32.5 ± 7.4 weeks versus 23.3 ± 6.5) and survivorship remained above 70% during the first 20 weeks. In parasite-exposed populations, life expectancy dropped from an overall 37.75 weeks to 11.35 weeks but still doubled the time for initial cercariae shedding. Cercariae shedding started at day 23 post-exposure and peaked between days 53 and 67 with an average of 106 metacercariae per snail.ConclusionsWhether O. viridis will succeed in Europe is unknown, but the odds are for a scenario in which a major snail host of F. hepatica occupy all available habitats of potential transmission foci, ravelling the epidemiology of fasciolosis. This research provides a comprehensive understanding of O. viridis biology, interactions with parasites and potential implications for disease transmission dynamics, offering valuable insights for further research and surveillance.Graphical

Exploring the second intermediate hosts and morphology of human- and cat-specific Opisthorchis viverrini-like populations

Infection by the zoonotic fish-borne trematode, Opisthorchis viverrini, remains a crucial health issue in Thailand and neighboring countries. Recently, molecular analysis revealed two populations of putative O. viverrini: one found primarily in human hosts (“human-specific” population) and the other primarily in cats (“cat-specific” population). It is unclear how the infective stages (metacercariae) of these different populations circulate among definitive and reservoir hosts in nature. To gain an insight into this, mitochondrial cox1 and nad1 gene sequences of metacercariae from fish intermediate hosts were examined. None of 192 metacercariae from cyprinid fish in Lao PDR and Thailand had sequences typical of “cat-specific” O. viverrini, suggesting that cyprinid fish are not the main second intermediate hosts of this population. Interestingly, all 20 O. viverrini-like metacercariae from snakehead fish (Channa striata) shared 99.51–100% sequence identity with eggs from cats naturally infected in a previous study. Hence, we propose a modification of the known transmission dynamics of O. viverrini: consumption of metacercariae within snakehead fish provides another pathway for cats and (occasionally) humans to acquire infection. We also performed morphological comparisons of eggs, metacercariae, and adult flukes (raised in hamsters) of both Opisthorchis populations. The “cat-specific” population has eggs that are narrower and adults that are shorter and wider than in the human-specific population. The metacercaria of the “cat-specific” population is elliptical, while that of the “human-specific” population is oval, occasionally rounded. Our results confirmed that O. viverrini-like metacercariae from snakehead fish are the infective stages of the “cat-specific” fluke. This provides a new insight into the dissemination and transmission of each population in the second intermediate host. The identity of the cat-specific population is discussed.

The Zoonotic Angiostrongylus cantonensis and the Veterinary Parasite Aelurostrongylus abstrusus Infecting Terrestrial Gastropods from Urban Areas of Macapá, Brazilian Amazon Region.

Metastrongyloidea includes nematodes that parasitize mammals, mainly infecting their respiratory and cardiovascular systems, and are responsible for emerging zoonosis in the world. Terrestrial mollusks are their main intermediate hosts, with few exceptions. Here we present the results of a malacological survey to know the distribution of Angiostrongylus cantonensis in Macapá, Amapá, in the Brazilian Amazon region, after the report of a case of eosinophilic meningitis in 2018. Mollusks were collected in 45 neighborhoods between March 2019 and February 2020. They were identified, parasitologically analyzed, and their nematodes parasites were identified based on the morphology and MT-CO1 sequencing. Infections of An. cantonensis were observed in Achatina fulica, Sarasinula linguaeformis and Subulina octona. These are the first records of the natural infection of the last two species by An. cantonensis in the Brazilian Amazon region. The angiostrongylid Aelurostrongylus abstrusus, which parasitizes cats, was also detected parasitizing A. fulica and Diplosolenodes occidentalis. This is also the first record of the slug D. occidentalis infected by Ae. abstrusus. The highest infection rates were recorded in neighborhoods where the environment conditions favor the proliferation of both mollusks and rodents. The results demonstrate the ample distribution of An. cantonensis in Macapá and the need for surveillance and mollusk vector control in Brazil and other countries.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry traces the geographical source of Biomphalariapfeifferi and Bulinusforskalii, involved in schistosomiasis transmission

BackgroundFreshwater snails of the genera Bulinus spp., Biomphalaria spp., and Oncomelania spp. are the main intermediate hosts of human and animal schistosomiasis. Identification of these snails has long been based on morphological and/or genomic criteria, which have their limitations. These limitations include a lack of precision for the morphological tool and cost and time for the DNA-based approach. Recently, Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight (MALDI–TOF) mass spectrometry, a new tool used which is routinely in clinical microbiology, has emerged in the field of malacology for the identification of freshwater snails. This study aimed to evaluate the ability of MALDI–TOF MS to identify Biomphalariapfeifferi and Bulinusforskalii snail populations according to their geographical origin.MethodsThis study was conducted on 101 Bi.pfeifferi and 81 Bu.forskalii snails collected in three distinct geographical areas of Senegal (the North-East, South-East and central part of the country), and supplemented with wild and laboratory strains. Specimens which had previously been morphologically described were identified by MALDI–TOF MS [identification log score values (LSV) ≥ 1.7], after an initial blind test using the pre-existing database. After DNA-based identification, new reference spectra of Bi.pfeifferi (n = 10) and Bu.forskalii (n = 5) from the geographical areas were added to the MALDI–TOF spectral database. The final blind test against this updated database was performed to assess identification at the geographic source level.ResultsMALDI–TOF MS correctly identified 92.1% of 101 Bi.pfeifferi snails and 98.8% of 81 Bu.forskalii snails. At the final blind test, 88% of 166 specimens were correctly identified according to both their species and sampling site, with LSVs ranging from 1.74 to 2.70. The geographical source was adequately identified in 90.1% of 91 Bi.pfeifferi and 85.3% of 75 Bu.forskalii samples.ConclusionsOur findings demonstrate that MALDI–TOF MS can identify and differentiate snail populations according to geographical origin. It outperforms the current DNA-based approaches in discriminating laboratory from wild strains. This inexpensive high-throughput approach is likely to further revolutionise epidemiological studies in areas which are endemic for schistosomiasis.

Alterations in the metabolism of Pseudosuccinea columella (Mollusca: Gastropoda) caused by Heterorhabditis bacteriophora HP88 (Rhabditida: Heterorhabditidae)

The gastropod Pseudosuccinea columella participates in the dissemination of Fasciola hepatica in the environment, acting as the main intermediate host of this parasite in Brazil. The present study sought to elucidate the possible pathogenic effects of the entomopathogenic nematode (EPN) Heterorhabditis bacteriophora on P. columella, by evaluating the influence of infection on alanine aminotransferase (ALT) and aspartate aminotransferase (AST), as well as the concentrations of total protein, uric acid, and urea in the snail's hemolymph. For this, the snails were exposed to EPNs for 24 and 48 h, and for each exposure time, 20 snails were dissected after 7, 14 and 21 days for hemolymph collection. The primary findings suggest a significant proteolysis alongside elevated levels of uric acid and urea in P. columella infected individuals. These findings reveal that H. bacteriophora HP88 infection induced serious changes in the snail's metabolism, triggering important deleterious effects.

Genetic characterization and regional distribution of lymnaeid snails in northern Patagonia, Argentina.

Lymnaeid snails serve as intermediate hosts for Fasciola hepatica (Linnaeus, 1758), the etiological agent of fasciolosis, which is a widespread livestock disease in Argentina. Determining their geographic distribution and identifying the snail species involved in the transmission of fasciolosis can provide crucial information for designing strategic control programs. In this context, this work aimed at genetically characterizing the species of lymnaeid snails collected in different water bodies of northern Patagonia, Argentina. To this end, 689 snails were collected in 12 sites in the provinces of Neuquén, Río Negro and Chubut, in areas where fasciolosis is endemic. According to the morphological characteristics of their valves, they were identified as Galba spp. Twenty-three of these specimens were further identified using the nuclear sequences of the internal transcribed spacers ITS-1 and ITS-2 and 18S rRNA. The results confirmed the identity of all the analyzed snails as Galba viatrix and provided evidence that studying the variable region V2 of the 18S rRNA gene is not enough to differentiate closely related species, as observed in lymnaeid snails. Both the fact that G. viatrix was the only species identified in the endemic area surveyed and previous evidence of the high prevalence of F. hepatica infestation in grazing animals in the region suggest that this species is the main intermediate host of F. hepatica. The correct identification of lymnaeid snail species has great importance to determine risk zones and develop appropriate control measures to reduce transmission, according to the different ecological characteristics of each species.

Review on Ruminant Fasciolosis in Ethiopia

Ethiopia possesses the largest livestock population in Africa. Ruminant Fasciolosis is a serious problem in animal production in different areas of the world especially in Ethiopia. It is a wide spread trematodal disease affecting ruminants (cattle, sheep and goats) and also other species of animals. F. hepatica and F. gigantica are the parasitic species belonging to Genus Fasciola under the phylum platyhelminths. The fasciola disease has three phases of clinical sign acute, sub-acute and chronic forms. Fasciolosis is more apparent in young ruminant and is usually chronic in nature. Adult flukes in the bile ducts cause inflammation, biliary obstruction, distraction of liver tissue and anemia. Snails of family Lymnaeidae are main intermediate hosts having great role on the transmission of the disease and the infection is acquired through grazing on swampy pasture. The disease mostly diagnosed by prior knowledge of the epidemiology of the disease in a given environment; observation of clinical signs, information on grazing history, seasonal occurrence and standard examination of feces in the laboratory. The affected cattle should be effectively treated with narrow spectrum anthelmintic such as Triclabendazole in addition to reducing the population of the intermediate host to control the disease. Now a days, fasciolosis is recognized as emerging human disease over the world even if only few case reports of human fascioliasis are available in Ethiopia, as the disease mostly affects animals in the country. The disease causes a significant economic loss in ruminant production by inflecting direct and indirect loss at different parts of Ethiopia. To control and prevent the disease, the strategic destruction of snail population should be implemented throughout the country to break down the life cycle of liver fluke.

Inhibition of alternative oxidase disrupts the development and oviposition of Biomphalaria glabrata snails

BackgroundBiomphalaria glabrata is one of the main intermediate hosts of Schistosoma mansoni, the most widespread species of Schistosoma. Our previous studies proved that alternative oxidase (AOX), the terminal oxidase in the mitochondrial respiratory chain, widely exists in several species of intermediate host snails of Schistosoma. Meanwhile, inhibition of AOX activity in Oncomelania hupensis snails could dramatically enhance the molluscicidal effect of niclosamide. As a hermaphroditic aquatic mollusc, the high fecundity and population density of B. glabrata increase the difficulty of snail control, which is one of the critical strategies for schistosomiasis elimination. The present study aimed to investigate the possible role of AOX in the development and fecundity of B. glabrata snail, which could be manipulated more manageable than other species of intermediate host snails of Schistosoma.MethodsThe dynamic expression of the AOX gene was investigated in different developmental stages and tissues of B. glabrata, with morphological change and oviposition behaviour observed from juvenile to adult snails. Furtherly, dsRNA-mediated knockdown of BgAOX mRNA and the AOX protein activity inhibiting was performed to investigate the effect of AOX on the development and oviposition of snails.ResultsThe BgAOX gene expression profile is highly related to the development from late juveniles to adults, especially to the reproductive system of snails, with a positive correlation of 0.975 between egg production and BgAOX relative expression in ovotestis of snails. The inhibition of BgAOX at the transcriptional level and AOX activity could efficiently inhibit snail growth. However, the interference at the BgAOX protein activity level led to more severe tissue damage and more significant inhibition of oviposition than at the transcriptional level. This inhibition of growth and oviposition decreased gradually with the increase in the snail size.ConclusionsThe inhibition of AOX could efficiently disrupt the development and oviposition of B. glabrata snails, and the intervention targeting AOX at the juvenile stage is more effective for snails. This investigation explored the role of AOX in the growth and development of snails. It would benefit snail control in the future by providing a potential target while using molluscicides more efficiently.Graphical abstract

Response of wild rodents to red fox feces: implication for the echinococcus infection.

Echinococcus multilocularis causes zoonotic disease, alveolar echinococcosis. The life cycle of E. multilocularis is maintained by the predator-prey relationship between red foxes and rodents. Infection to red fox (Vulpes vulpes) of E. multilocularis is considered that rodents take eggs of E. multilocularis, then red fox forage the rodents. However, it has been not known how to take eggs by rodents. On infection process of E. multilocularis from red foxes to rodents, we predicted that rodents would forage or touch with feces of red fox to use undigested materials within the feces. We monitored rodent's response to fox feces and their distance to the feces by using camera trap from May to October 2020. Myodes spp. and Apodemus spp. touched fox feces, and touch rate of Apodemus spp. was significantly higher than that of Myodes spp. We found smelling and passing as contact behaviors to fox feces by Myodes spp., while Apodemus spp. showed behaviors which oral directly contacted feces. There was no significant difference on the shortest distance between Apodemus spp. and Myodes spp. The distance between 0 cm and 5 cm was mostly observed for both rodents. The results that Myodes spp. did not forage feces and their contact to feces was low frequency suggested that the infection from red foxes to Myodes spp., the main intermediate host, was to be other pathways. The approach to feces and the act near feces might increase the probability attached with eggs.

DISTRIBUTION PATTERNS OF METACERCARIAE OF THE TREMATODA <i>APOPHALLUS </i><i>MUEHLINGI</i> (JÄGERSKIÖLD, 1899) IN UNDERYEARLINGS IN AN INVASIVE POPULATION OF <i>CLUPEONELLA CULTRIVENTRIS</i> (NORDMANN, 1840) FROM THE GORKY RESERVOIR (UPPER VOLGA BASIN)

After the successful naturalization of the prosobranch mollusk Lithoglyphus naticoides (C. Pfeiffer, 1828) and a number of associated trematodes in the Gorky Reservoir (in 2005-2015) an intensive spread of apophallesis in fish of this water body has been observed. As one of the second intermediate hosts of the trematode causing this disease, Apophallus muehlingi (Jägerskiöld, 1899), a freshwater form of the Black Sea-Caspian kilka Clupeonella cultriventris (Nordmann, 1840) was recorded. The aim of the work is to study the consequences of dispersal of C. cultriventris for the formation of large permanent foci of apophallesis in the Upper Volga. For comparison, data on the spread of this type of "black-spot" disease in the populations of C. cultriventris from the Gorky Reservoir and an unregulated area of the Lower Volga (downstream the cascade of Volga reservoirs, pelagic trawl coordinates from 47°08ʹN, 47°17ʹE to 46°51ʹN, 47°41ʹE) were used. The high rates of occurrence of A. muehlingi metacercariae (the infection prevalence P, %) are recorded in the fall along the entire area of the Gorky Reservoir: from the northernmost site near Rybinsk (58°01ʹN, 39°06ʹE) to the dam area (56°41ʹN, 43°21ʹE). It is found that the distribution pattern of A. muehling metacercariae varies in the sections of the reservoir differing in hydrological characteristics. In the middle (transitional type) section of the reservoir the prevalence of A. muehlingi metacercariae in groups of the smallest Black Sea-Caspian kilka fingerlings (with a body length of up to 45 mm), is close to the maximally possible (30.00-94.49%). In the upper (river-type) section of the reservoir, the prevalence of metacercariae in this group of fish does not exceed 24.39%. The minimum values of this indicator are found in the lower (lake-type) section of the reservoir (6.76-14.84%). Judging by the values of the abundance index and the coefficient of variation in the infection intensity, the aggregation of metacercariae is more pronounced in the groups of faster growing underyearlings and the Black Sea-Caspian kilka yearlings as compared to the groups of the smallest fingerlings. In the Black Sea-Caspian kilka fingerlings samples from the Lower Volga in 2020 reveals no statistically significant differences between the infection prevalence values (13.33-18.11%) in the different size groups. Thus, although the main second intermediate hosts of A. muehlingi are various fish species of the Cyprinidae family, in some cases the presence of C. cultriventris in the water body ecosystem can significantly increase the likelihood of apophallesis spread. In conditions of the Upper Volga, due to the high migration activity of large individuals of the Black Sea-Caspian kilka, a continuous zone of apophallesis can form without clearly defined boundaries between the individual foci of disease.

Seroprevalence and genetic characterization of Toxoplasma gondii in domestic pigs intended for human consumption in Cuba.

Domestic pigs are considered as one of the main intermediate hosts in the zoonotic transmission of Toxoplasma gondii in many countries. Serological and molecular studies are warranted to better understand the epidemiology and transmission patterns of this parasite worldwide. To date, seroepidemiological information on T.gondii in domestic pigs in Cuba is very scarce and there are no reports of T.gondii genotypes circulating in this country. Here, we aimed to estimate the seroprevalence of T.gondii and provide genetic characterization of the strains circulating in slaughtered pigs intended for human consumption in Central Cuba. Seroprevalence was determined in 450 serum samples from slaughtered pigs in Villa Clara province using ELISA. Anti-Toxoplasma gondii IgG antibodies were detected in 100 animals (22.2%, 95% CI: 18.5-26.2). Conventional PCR of the 529-bp marker of T.gondii was performed in hearts and diaphragm tissues of all ELISA-seropositive pigs. Toxoplasma gondii DNA was detected in four animals. Further genetic characterization of the positive DNA samples was performed by multilocus PCR-RFLP and PCR-sequencing typing tools. Molecular analysis revealed four different genetic profiles that were combinations of type I, II, III and u-1 alleles, suggesting the circulation of non-clonal genotypes of T.gondii in domestic pigs in Cuba. Our results indicate that T.gondii is widely distributed in slaughtered pigs in this country, which might have important implications for public health. To the best of our knowledge, this is the first report on genetic characterization of T.gondii in Cuba. Although preliminary, the results suggest a high genetic diversity of T.gondii in the study region. Further studies based on parasite isolation are needed to definitively identify the genotypes circulating and characterize the virulence of strains detected in pigs in Cuba, and to assess the risk of zoonotic transmission from pork products in this country.

Global epidemiology and molecular biology of Taenia multiceps: a comparative meta-analysis and in silico analysis study.

In the present study, all published data on the epidemiology and molecular characters of Taenia multiceps were systematically collected from relevant databases (e.g. PubMed, Scopus, National Center for Biotechnology Information), and combined in various statistical and genetic analyses as a contribution to a better understanding of the epidemiology of this ubiquitous taeniid worldwide. While 5.8% of the key hosts (dogs) from various countries had T. multiceps, grey wolves displayed the highest prevalence (21.6%) among the definitive hosts. Small ruminants are the main intermediate hosts and carry the coenuri in various locations, but most commonly in the central nervous system (CNS). Cerebral coenuri were confirmed in 53% of sheep exhibiting neurological symptoms, and infected animals often had only a single coenurus in the brain. Sheep had a higher prevalence (8.8%) of CNS coenuri than goats (5.8%); however, extra-CNS coenuri were detected more frequently in goats than in sheep. In either case, the difference between sheep and goats was statistically insignificant. Analysis of 233 partial cytochrome oxidase subunit I nucleotide sections for T. multiceps revealed high haplotype and low nucleotide diversities. Fifty-one haplotypes were detected circulating in 6 geographic populations. China, Iran and Turkey had 2 major haplotypes, whereas Italy and Egypt shared 3. Haplotypes from Greece circulate worldwide, and displayed similar gene flow values when compared with the other populations. There were no distinct patterns for haplotype distribution in relation to the infected hosts or coenuri locations. The existence of genetic variants in T. multiceps was highlighted, but needs further studies.

Molecular Identification of Parasitic Protozoa Sarcocystis in Water Samples.

Simple SummaryMembers of the genus Sarcocystis are protozoan parasites having two-host prey–predator cycle. These parasites are widespread in farm animals. Sarcocystis species are characterized morphologically in intermediate hosts, and these parasites are identified in definitive hosts by molecular methods. Thus far, only few studies have been conducted on Sarcocystis parasites in environmental samples. The aim of the present work was to evaluate several sample preparation and polymerase chain reaction methods for the identification of several Sarcocystis species in water samples. Overall, 114 samples collected from various water sources, ponds, canals, lakes, lagoons, and rivers in Lithuania were tested for the presence of Sarcocystis spp. Based on molecular methods, eight Sarcocystis species, S. bovifelis, S. cruzi, S. hirsuta, S. arieticanis, S. tenella, S. capracanis, S. bertrami, and S. miescheriana, were identified. The main intermediate hosts of detected Sarcocystis parasites are cattle, sheep, goats, horses, and pigs. Further, more sensitive molecular techniques are needed for the development of the diagnosis of Sarcocystis species in water bodies.Sarcocystis parasites are among the most common parasitic protozoa in farm animals. So far, the diversity of these parasites has been mainly studied in animal carcasses by morphological or molecular methods. Research on parasitic protozoa in environmental samples is scarce due to the lack of an appropriate methodology and low concentrations of parasites. For these reasons, there is a paucity of validated methods for Sarcocystis identification from environmental samples. Therefore, the present study aims to investigate various molecular methods for Sarcocystis parasite identification in water samples. In the present study, the sample volume, sporocysts isolation, and various conventional PCR were evaluated, and species-specific primers for the identification of different Sarcocystis species have been developed. Of the methods studied, based on data the most appropriate method for the identification of analyzed Sarcocystis spp. in water bodies is nested PCR, using species-specific primers targeting the cox1 gene. Sarcocystis DNA was detected in 111 out of 114 (97.4%) samples. This paper represents the first identification of S. bovifelis, S. cruzi, S. hirsuta, S. arieticanis, S. tenella, S. capracanis, S. bertrami, and S. miescheriana by PCR and sequencing in environmental water samples. Our pilot study is useful in developing techniques for the identification of Sarcocystis species from water samples.

Potential risk of colonization of Bulinus globosus in the mainland of China under climate change

BackgroundBulinus globosus, the main intermediate snail host of Schistosoma haematobium. The increased contacts between Africa and China could even lead to large-scale dissemination of B. globosus in China. Temperature is the key factor affecting fresh-water snail transmission. This study predicted potential risk of colonization of B. globosus in the mainland of China under climate change.MethodsWe investigated minimum and maximum temperatures for B. globosus eggs, juveniles and adult snails kept under laboratory conditions to find the most suitable range by pinpointing the median effective temperatures (ET50). We also assessed the influence of temperature on spawning and estimated the accumulated temperature (AT). The average air temperatures between 1955 and 2019 in January and July, the coldest and hottest months in China, respectively, were collected from national meteorological monitoring stations and investigated in a geographic information system (GIS) using empirical Bayesian Kriging to evaluate the theoretical possibility for distribution of B. globosus in southern China based on temperature.ResultsThe effective minimum temperature (ET50min) for eggs, juveniles, adult snails and spawning were 8.5, 7.0, 7.0, 14.9 °C, respectively, with the corresponding maximum values (ET50max) of 36.6, 40.5, 40.2 and 38.1 °C. The AT was calculated at 712.1 ± 64.9 °C·d. In 1955, the potential B. globosus distribution would have had a northern boundary stretching from the coastal areas of Guangdong Province and Guangxi Autonomous Region to southern Yunnan Province. Since then, this line has gradually moved northward.ConclusionsAnnual regeneration of B. globosus can be supported by the current climate conditions in the mainland of China, and a gradual expansion trend from south to north is shown in the study from 2015 to 2019. Thus, there is a potential risk of colonization of B. globosus in the mainland of China under climate change.Graphical

New Data on Pipefishes' and Seahorse's Endohelminths Off Crimean Coasts of The Black Sea.

SummaryA total of 357 Syngnathidae fishes (Syngnathus abaster Risso, 1827, S. typhle Linnaeus, 1758 and Hippocampus hippocampus (Linnaeus, 1758) caught in different habitats along Crimean Black Sea shelf were examined for presence of endohelminths and revealed to be hosts of 15 helminth species. The fishes are second intermediate hosts for five “birds’” digenean species and nematodes (larvae of three species and immature adults of one more species) completing life-cycles in waterbirds and fish; for two acanthocephalans and three cestodes larvae ending development in fish. We suggest, basing on data on feeding of the Black Sea predatory fish and waterbirds, that Syngnathid fishes are paratenic hosts in parasitic systems of most cestodes, nematodes and acanthocephalans. All the trematodes found are generalists at metacercarial stage; specialists Timoniella imbutiformis and Aphallus tubarium use Syngnathidae as definitive hosts. Cestodes, nematodes as well as acanthocephalans found are generalists, too. Based on infection indices, S. typhle are main final host and H. hippocampus are main 2nd intermediate hosts for T. imbutiformis; Syngnathids are accidental hosts for other trematodes as well as for all the cestodes, nematodes and acanthocephalans. Cryptocotyle concava and Pygidiopsis genata are important as Syngnathid fishes’ threats, especially in marine protected aquatoria, being potential agents of “black spot disease”.

Ecological and parasitological characteristics of the “Fasciola hepatica L.–Lymnaea (Galba) subangulata” system

Background. Fasciolosis is one of the most common zoonoses in the world, caused by the trematode Fasciola hepatica L. This helminthiasis leads to significant economic damage in animal husbandry and can pose a direct threat to human health. Today, in the context of climate change, detailed knowledge of the biological characte­ristics of the trematode F. hepatica circulation will make it possible to predict outbreaks of fasciolosis on farms in detail and plan effective measures to combat this dangerous disease. The purpose of this work is to clarify some aspects of F. hepatica biology within Berdychiv district belonging to the forest-steppe zone of Zhytomyr region. Material and Methods. The work was carried out during 2020–2021. Collections of mollusks from water bodieson the territory of Berdichevsky district of Zhytomyr region served as the material for the research. Their identification was carried out by conchological features. Conventional methods were used for the parasitological study of mollusks. In total, more than 2000 mollusks Lymnaea (Galba) spp. were examined. Sampling of water and mollusks was carried out from four pasture reservoirs. Results. The main intermediate host of F. hepatica is the mollusk L. (G.) subangulata in the territory of Berdychiv region; L. (G.) truncatulaplays a secondary role in the distribution of this trematode. It was noted that the carriers of F. hepatica partenites are mainly mollusks with a shell height of 4.0 to 8.2 mm. New data on the dynamics of infection of L. (G.) subangulata with the trematode F. hepatica was obtained. The dynamics of infestation of these mollusks with F. hepatica cercariae shows a stable uniform character in the form of a two-peak curve, with peaks in May (2.51 ± 0.88 %) and August (9.19 ± 1.78 %). The overall prevalence of L. (G.) subangulata invasion by fasciola cercariae in the studied water bodies in 2020 was significantly lower than in 2021. Conclusions. In modern climatic conditions, in the territory of the region, permanent water bodies have become fasciolosis foci and common places for the settlement of L. (G.) subangulata, infected with F. hepatica cercariae. The most favorable environmental conditions for fasciola and its intermediate hosts develop in spring; accordingly; for the definitive hosts, this period is quite dangerous in terms of infection of animals.

Heterorhabditis bacteriophora (Rhabditida: Heterorhabditidae), isolate HP88, induces reproductive and physiological alterations in Biomphalaria glabrata (Gastropoda: Planorbidae): an alternative for biological control of schistosomiasis

Heterorhabditis bacteriophora is an entomopathogenic nematode (EPN) that is mutually associated with Photorhabdus luminescens, utilized globally for biological control of numerous organisms. Freshwater snails of the species Biomphalaria glabrata have been incriminated as the main intermediate hosts of Schistosoma mansoni in Brazil, but virtually nothing is known about the susceptibility of these gastropod to EPNs. Information in this respect is relevant for control of these intermediate hosts, and thus of the helminthiases they transmit. This paper for the first time reports the susceptibility of B. glabrata to infective juveniles of H. bacteriophora (isolate HP88) under laboratory conditions. For that purpose, six groups were formed: three Control groups (not exposed) and three Treated groups, in which the snails were exposed to 300 juveniles infecting the nematode over three weeks. The entire experiment was conducted in triplicate, using a total of 270 snails. Significant physiological alterations in B. glabrata were observed in response to the infection by H. bacteriophora HP88, characterized by decreased levels of hemolymphatic glucose as well as reduced contents of glycogen stored in the host's digestive gland. In parallel, the hemolymphatic activity of lactate dehydrogenase increased in the infected snails, indicating that the infection induces breakdown of carbohydrate homeostasis in B. glabrata. Additionally, all the reproductive parameters analyzed were reduced as a consequence of the infection. The results indicate the occurrence of the phenomenon of parasitic castration in the B. glabrata/H. bacteriophora HP88 interface, probably due to the depletion of galactogen in the parasitized organism. Although the infection did not cause lethality in the population of infected snails, H. bacteriophora HP88 compromised the reproductive performance of B. glabrata, suggesting its applicability in programs for biological control of this planorbid.

Complete mitochondrial genome of the freshwater snail Tarebia granifera (Lamarck, 1816) (Gastropoda: Cerithioidea: Thiaridae)

The freshwater gastropod Tarebia granifera (Lamarck, 1816) is found in Taiwan, Hainan, and Guangdong provinces in China, and is one of the main intermediate hosts of trematodes that infect humans. The taxonomic positions of some cerithioidean families are still unclear, and whole mitochondrial genome studies are scarce in the Thiaridae. In this study, we describe the complete mitogenome of Tarebia granifera (Lamarck, 1816). The mitogenome is 15,555 bp in length, with a total of 37 genes, including 13 protein-coding genes, 2 rRNA genes, and 22 tRNA genes. It is consistent with the essential features of previously studied mitochondrial genomes of species belonging to the superfamily Cerithioidea. Our study demonstrates the usefulness of mitogenomic data for resolving phylogenetic relationships of families within Cerithioidea and may also contribute to the prevention and control of the parasitic diseases caused by trematodes, which use T. granifera as an intermediate host.

MORPHOLOGICAL AND BIOINFORMATICS STUDY FOR RADIX AURICULARIA SNAILS IN FRESHWATER IN BASRAH PROVINCE, IRAQ

Radix auricularia (Lymnaea auricularia) snails are the main intermediate host of Fasciola gigantica in the middle and South of Iraq. Recently, some studies suggest these snails are not present in Iraq, in particular Basrah province. Thus, the current study was aimed to use the bioinformatics analysis in the determination of Radix sp. in Basrah and also aimed to identify morphological characteristics of this species in the AL-Sewaib river, Basrah. Four hundred R. auricularia snails were collected from the AL-Sewaib river during May 2018 to March 2019. The results of the bioinformatics analysis showed according to the mitochondrial cytochrome c oxidase subunit I, the presence of R. auricularia snails in Basrah province and these snails are more closely related to Iranian R. auricularia snails than those for European counties and Russia. This study also displayed the existence of the polymorphism phenomenon in R. auricularia snails collected from the AL-Sewaib river which there were six different forms (A, B, C, D, E and F). These forms had variations in the colour and form of shells along with a variation in the number of eggs (30-56) per an egg mass. In addition to this, these R. auricularia forms had variations in their distributions. Form E had the highest spread percentage (33%) followed by 17, 15, 14, 11 and 10% for forms B, D, C, A and F, respectively. These forms had also variations in their morphological characteristics. The largest form was the form D whereas the smallest form was the form B but other forms A, C, E and F were similar and had moderate sizes.Thus, the current study concludes the existence of R. auricularaia snails in Basrah as a representative city for the southern part of Iraq and also confirmed the presence of the polymorphism phenomenon in the members of R. auricularaia obtained from the AL-Sewaib river.

Can animals like bats, pangolins, and ticks would be considered as long-term reservoirs of severe acute respiratory syndrome coronavirus 2

In December 2019, there was an outbreak of pneumonia with an unknown cause in Wuhan, Hubei province, China. Within less than 3–4 months, the virus has spread to more than 200 countries. The virus rapidly transmitted from different places of the world with various cultural traditions. Thereby, the question is remained to be resolved about the main intermediate carrier of diseases in different animals. Studied showed that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was originated from horseshoe bats, but its intermediate hosts are still largely unknown. Therefore, the possibility of horseshoe bat infection by ticks is high during the flight between plants or when resting in these places. Female ticks can either feed on horseshoe bat blood for 5–7 days before shedding or can form large aggregations by laying several thousand eggs in the right places or on them. Once they feed on horseshoe bat blood containing SARS-CoV-2, they can transfer the infection to the next generations without the need to reuse infections from the reservoir host. With all the potential features that this creature has, it is mandatory to investigate the presence or absences of SARS-CoV-2, especially when we know that ticks co-exist with that horseshoe bats. These factors highlight the importance of studying the viral epidemiology in the tick population. Thereby, based on the wide distribution of ticks and their co-existence with horseshoe bat, we suggest further studies on ticks that might act as one of the main intermediate hosts in different animals.