Trematode Research Articles

Effects of larval trematode parasitism on the reproductive capacity of Manila clam Ruditapes philippinarum in a sandy-mud tidal flat on the west coast of Korea

Gonad intrusion of the larval trematodes often results in substantial damage to the reproductive capacity of some economically important marine bivalves. Such detrimental impacts of the larval trematode infection are observed in Manila clam Ruditapes philippinarum in the coastal Yellow Sea, although the effects on the host’s reproduction are poorly understood. Accordingly, this study attempts to understand the impacts of parasitism on clam reproduction using histology. Of the 1,255 adult clams collected in early June from a tidal flat on the west coast of Korea, 68 individuals (5.4%) were infected by three different larval trematodes, including Cercaria tapidis, Cercaria pectinata, and Parvatrema duboisi. Histology revealed that the uninfected clams were in the late developing or ripe stage, exhibiting fully developed gametes in the expended follicles. In contrast, clams infected by the larval trematode showed retarded gonad maturation. Some of those clams remained sexually indifferent (13/68 infected clams) or early developing (9/68 infected clams). We categorized the infection level into uninfected (0), light (1), moderate (2), heavy (3), and very heavy (4), according to the area of sporocysts occupying the histology section. The image analysis indicated that approximately 50% of the infected clams were in “heavy” and “very heavy” conditions, and they occupied 16.7% and 26.9% of the total cross-section area, respectively. The nonparametric Kruskal–Wallis’s test and the post-hoc Tukey’s test indicated that the condition index (CI) of clams in heavy and very heavy infection were significantly lower than uninfected clams. In conclusion, the larval trematodes infected about 5.4% of the clam population in the tidal flat on the west coast of Korea, and we estimated that 32.4% of the infected clams might fail to reproduce during a spawning period due to the severe infection.

Trematode infection affects shell shape and size in Bulinus tropicus.

Trematodes can increase intraspecific variation in the phenotype of their intermediate snail host. However, the extent of such phenotypic changes remains unclear. We investigated the influence of trematode infection on the shell morphology of Bulinus tropicus, a common host of medically important trematodes. We focused on a snail population from crater lake Kasenda (Uganda). We sampled a single homogeneous littoral habitat to minimize the influence of environmental variation on shell phenotype, and barcoded snails to document snail genotypic variation. Among the 257 adult snails analysed, 99 tested positive for trematode infection using rapid-diagnostic PCRs. Subsequently we used high-throughput amplicon sequencing to identify the trematode (co-)infections. For 86 out of the 99 positive samples trematode species delineation could discriminate among combinations of (co-)infection by 11 trematode species. To avoid confounding effects, we focused on four prevalent trematode species. We performed landmark-based geometric morphometrics to characterize shell phenotype and used regressions to examine whether shell size and shape were affected by trematode infection and the developmental stage of infection (as inferred from read counts). Snails infected by Petasiger sp. 5, Echinoparyphium sp. or Austrodiplostomum sp. 2 had larger shells than uninfected snails or than those infected by Plagiorchiida sp. Moreover, the shell shape of snails infected solely by Petasiger sp. 5 differed significantly from that of uninfected snails and snails infected with other trematodes, except from Austrodiplostomum sp. 2. Shape changes included a more protuberant apex, an inward-folded outer apertural lip and a more adapically positioned umbilicus. Size differences were more pronounced in snails with ‘late’ infections (>25 days) compared to earlier-stage infections. No phenotypic differences were found between snails infected by a single trematode species and those harbouring co-infections. Further work is required to assess the complex causal links between trematode infections and shell morphological alterations of snail hosts.

Detection of schistosome infection in the invasive snail Melanoides tuberculata (Gastropoda: Thiaridae) by polymerase chain reaction from Plateau State, Nigeria: a novel turning point in disease epidemiology and control?

Melanoides tuberculata is a freshwater snail that serves as an intermediate host for 11 parasitic flukes. This study was conducted with the aim of identifying and screening the snail intermediate hosts in the study site for schistosomiasis using the molecular technique. DNA was extracted from the snails by the hexadecyl trimethyl ammonium bromide method and the Dra1 primer was used to amplify the Dra1 repeated sequence of Schistosoma haematobium. The presence of schistosome DNA in M. tuberculata by polymerase chain reaction was confirmed. Our findings show that M. tuberculata is a potential intermediate host of schistosomes.

Contamination of Vector Snails with the Larval Stages of Trematodes in Selected Areas in Northern Iran.

Identification of freshwater snails and possible trematodes transmission sites are essential to continue monitoring the potential for disease outbreaks in areas with a history of parasitic infections. We aimed to search some areas in the margin of the Caspian Sea, northern Iran to identify the snail fauna of this area and verify the contamination of vector snails. More than 5,308 snails from 51 diverse and permanent habitats were studied from April 2019 to October 2021. Snails were collected randomly and identified using shell morphology. Trematode infection in snails was investigated by the release of cercariae and dissection methods. Five families of freshwater snails including Lymnaeidae, Physidae, Planorbidae, Bithyniidae, and Viviparidae were investigated in the Caspian Sae Litoral of Iran. Physidae were found as the most prevalent snails (55.1%) followed by Lymnaeidae (29.4%). The parasitize rate was observed as 20% using releasing cercaria technique. Echinostomatoidea (31%), Schistosomatoidea (8%), and Diplostomoidea (21%), and Plagiorchioidea (40%) were seen as detected parasites. Meanwhile, 60% of the studied snails illustrated the other stages of trematodes. The rate of infection of snails with different cercaria in northern Iran is significant. It needs further deep studies to clarify the situation of zoonoses transmitted by snails in the region. Policy makers should pay attention more to this area in terms of monitoring the snail-transmitted diseases.

Serological evaluation of the schistosome’s secretory enzyme phytochelatin synthase and phosphoglycerate mutase for the detection of human Schistosoma japonicum infection

Secretory enzymes from Schistosoma japonicum are promising candidate antigens in the diagnosis of schistosomiasis. Our previous studies have proven that thioredoxin peroxidase-1 (SjTPx-1) is useful for the detection of this parasitic disease in humans, water buffaloes, and dogs. In this study, we evaluated two more secretory enzymes namely phosphoglycerate mutase (SjPGM) and phytochelatin synthase (SjPCS) with SjTPx-1 as the reference antigen. SjPGM was shown to have good diagnostic potentials in animal samples in previous studies, whereas SjPCS was chosen because of its absence in the mammalian hosts. Serum samples including 96 endemic negative controls, 107 schistosomiasis japonica positive samples, and 31 samples positive for other parasitic trematode infections (Clonorchis sinensis, Opisthorchis viverrini, Paragonimus westermani) were tested with the antigens using enzyme-linked immunosorbent assay. Results showed that SjPCS detected more positive samples and had fewer cross-reactions than SjPGM. With 85.05% sensitivity and 93.55% specificity, SjPCS can therefore be used in the detection of human schistosomiasis.

Identification of new polymorphic positions in rDNA sequences of the "intermediate" Fasciola forms.

Fascioliasis is a foodborne zoonotic disease generally caused by the parasitic flukes Fasciola gigantica and Fasciola hepatica in class Trematoda. An "intermediate" Fasciola forms between F. gigantica and F. hepatica has been shown to exist. However, the relationships among F. gigantica, F. hepatica, and "intermediate" Fasciola forms remain unclear. In this study, we found five new polymorphic positions in 18S and 28S rDNAs sequences of "intermediate" Fasciola forms. According to the high-throughput sequencing results, all known 16 polymorphic positions of "intermediate" Fasciola forms show a clear and consistent tendency for F. gigantica or F. hepatica, and the percentages of the most frequently occurring bases were different in specimens. In the three ITS sequence fragments, hybrid-type base combinations of the polymorphic positions were detected, and the percentages of the most frequent base combinations were different in specimens too. In addition, interestingly, the newly detected ITS-802 position was not a traditional polymorphic position in "intermediate" Fasciola forms, and the bases in ITS-802 position are not same as the allele bases of F. gigantica or F. hepatica. Our results will be helpful to investigations into the molecular taxonomy, population genetics, and ecology of F. gigantica, F. hepatica, and "intermediate" Fasciola forms.

General overview of the current status of human foodborne trematodiasis.

Foodborne trematodes (FBT) of public health significance include liver flukes (Clonorchis sinensis, Opisthorchis viverrini, O. felineus, Fasciola hepatica and F. gigantica), lung flukes (Paragonimus westermani and several other Paragonimus spp.) and intestinal flukes, which include heterophyids (Metagonimus yokogawai, Heterophyes nocens and Haplorchis taichui), echinostomes (Echinostoma revolutum, Isthmiophora hortensis, Echinochasmus japonicus and Artyfechinostomum malayanum) and miscellaneous species, including Fasciolopsis buski and Gymnophalloides seoi. These trematode infections are distributed worldwide but occur most commonly in Asia. The global burden of FBT diseases has been estimated at about 80 million, however, this seems to be a considerable underestimate. Their life cycle involves a molluscan first intermediate host, and a second intermediate host, including freshwater fish, crustaceans, aquatic vegetables and freshwater or brackish water gastropods and bivalves. The mode of human infection is the consumption of the second intermediate host under raw or improperly cooked conditions. The major pathogenesis of C. sinensis and Opisthorchis spp. infection includes inflammation of the bile duct which leads to cholangitis and cholecystitis, and in a substantial number of patients, serious complications, such as liver cirrhosis and cholangiocarcinoma, may develop. In lung fluke infections, cough, bloody sputum and bronchiectasis are the most common clinical manifestations. However, lung flukes often migrate to extrapulmonary sites, including the brain, spinal cord, skin, subcutaneous tissues and abdominal organs. Intestinal flukes can induce inflammation in the intestinal mucosa, and they may at times undergo extraintestinal migration, in particular, in immunocompromised patients. In order to control FBT infections, eating foods after proper cooking is strongly recommended.

Behavioral effects and inflammatory markers in the brain and periphery after repeated social defeat stress burdened by Opisthorchis felineus infection in mice

The combination of 4-week repeated social defeat stress (RSDS) and Opisthorchis felineus infection was modeled in C57BL/6 mice. Various parameters were compared between three experimental groups of male mice (SS: mice subjected to RSDS, OF: mice infected with O. felineus, and OF + SS: mice subjected to both adverse factors) and behavior-tested and intact (INT) controls. The combination caused liver hypertrophy and increased the blood level of proinflammatory cytokine interleukin 6 and proteolytic activity of cathepsin B in the hippocampus. Meanwhile, hypertrophy of the spleen and of adrenal glands was noticeable. Anxious behavior in the elevated plus-maze test was predominantly due to the infection, with synergistic effects of an interaction of the two adverse factors on multiple parameters in OF + SS mice. Depression-like behavior in the forced swimming test was caused only by RSDS and was equally pronounced in SS mice and OF + SS mice. Helminths attenuated the activities of cathepsin B in the liver and hypothalamus (which were high in SS mice) and increased cathepsin L activity in the liver. The highest blood level of corticosterone was seen in SS mice but was decreased to control levels by the trematode infection. OF mice had the lowest level of corticosterone, comparable to that in INT mice. Thus, the first data were obtained on the ability of O. felineus helminths—even at the immature stage—to modulate the effects of RSDS, thereby affecting functional connections of the host, namely “helminths → liver↔brain axis.”

Trematode Infection in a Freshwater Snail Hydrobioides Nassa (Gastropoda: Bithyniidae) in Thailand.

Summary1,024 individuals of Hydrobioides nassa were collected from 12 different localities in eight provinces from north, west, and central regions of Thailand. The infection of parasitic trematodes was investigated using shedding and crushing methods to search for cercariae and metacercariae. Trematode infection was found at a relatively low prevalence of 5.57%. Five different morphological types of cercariae were detected; xiphidio, monostome, mutabile, ophthalmoxiphidio, and microcercous, and three different morphological types of unknown metacercariae were observed. Microcercous cercariae of the lung fluke genus Paragonimus is reported here for the first time in a bithyniid snail. Our current finding show that H. nassa can serve as intermediate host for a range of parasitic trematodes in Thailand.

DIAGNOSTICS, PREVENTION AND THERAPY OF HELMINTH INFECTIONS OF THE RED DEER IN THE KALININGRAD REGION

The research purpose is to identify and study parasite fauna of the red deer in the Kaliningrad Region, to determine intermediate hosts of helminths and their role in the spread of helminth infections of animals, and to study the efficacy of new domestic drugs Monizen-forte, Iversan and Gelmicide produced by NVC Agrovetzashchita, LLC against the main helminth infections of the deer. We ran diagnostics of European red deer (Cervus elaphus) for helminthiasis by helminthoscopic methods on Kaliningrad Region reindeer farms from 2018 to 2021. We identified 45 helminth species in red deer in the Kaliningrad Region. Of these, 6 trematode species, 4 cestode species and 35 nematode species. The dehelminthization used the following domestic antiparasitic drugs produced in NVC AVZ, LLC: Monizen-forte, Iversan and Gelmicide, whose therapeutic efficacy was 100% for nematode infections, and 95% for trematode and cestode infections. The drugs are well tolerated and do not cause any local irritation or allergic reactions on the skin and mucous membranes. We conducted dehelminthization of 3 groups of deer three times a year: in March, July and October 2021. The obtained study results made it possible to develop and take veterinary measures to treat and prevent helminth infections of antler deer in the Kaliningrad Region.

OPISTHORCHIDES OF THE AMERICAN MINK (NEOVISON VISON) IN NATURAL BIOCENOSIS OF CENTRAL RUSSIA

The research purpose was to identify helminth infections caused by the Opisthorchidae family in the American mink in its natural habitats. The material for this work was helminths collected from carcasses of the American mink during 2011–2021. We mashed up the liver in warm physiological saline, opened the cavity of the gallbladder and bile ducts with ophthalmic scissors, allowed to stand and examined the residue for trematode eggs and helminth marita. The detected flat worms were differentiated using the identification guide by D. P. Kozlov (1977). A total of 32 fur animals were studied during the reporting period. As a result of the research, 3 species of opisthorchides were identified. Pseudamphistomum truncatum was detected in 18 animals (56.3%). Areas contaminated by helminths were detected in the Ryazan Region. Metorchis albidus was found in minks in two cases (6.3%) with an infection rate of 6 and 11 trematodes per animal. Сontaminated territories were recorded in the Vladimir and Ryazan Regions. An Opisthorchis felineus pathogen was found in one mink (3.2%) in the Ryazan Region. Functional foci of trematodiases of the American mink were detected in the Central region of Russia (Vladimir and Ryazan Region). Pathogens of trematode infections of the family Opisthorchidae were recorded in the gallbladder of the animal's liver.

Prevalence of fish-borne zoonotic trematode infection in Jilin Province, China.

Fish-borne zoonotic trematodes (FZTs) are the most serious food-borne parasites in Asia and have become a burden to public health and a new challenge in food safety. In Jilin Province, China, the prevalence of FZTs in intermediate and definitive hosts has not been extensively explored. In the present study, we investigated the prevalence of FZTs in Jilin Province, China. From July to November 2020, a total of 132 freshwater snails (the first intermediate host of FZTs), 4122 wild freshwater fishes (the second intermediate host of FZTs) and 143 fecal samples from canines, ducks and swine (the definitive host of FZTs) were collected from the Yitong River basin of Jilin Province. FZT species were identified by morphological observation combined with internal transcribed spacer (ITS) sequence analysis. The prevalence of FZTs was then calculated. The results showed that the prevailing species of FZTs in Jilin Province, China, were Clonorchis sinensis, Metorchis orientalis and Echinochasmus japonicus. The total prevalence of FZTs was 29.74% (1226/4122) in fish, the total infection rates were 2.27% (3/132) in snails, 75.00% (21/28) in canines and 37.18% (29/78) in ducks. The coinfection rates of the two trematodes were 13.39% (552/4122) in fish, 35.71% (10/28) in canines and 7.69% (6/78) in ducks. The coinfection rate of the three flukes was 2.60% (107/4122) in fish. Nine of the 12 fish species examined were infected with FZT metacercariae.

Digenetic Trematode parasites in two fresh water fishes Ophiocephalus punctatus and Xenentodon cancila from North west Himalayas.

The study was conducted during September 2018-August 2019 to study the digenetic trematode infection in fresh water fishes of some of the water bodies viz. Gho-manhasan, Chakrali and Chadwal of Jammu region of J&K union territory. A total of 220 fishes comprising Ophiocephalus punctatus and Xenentodon cancila belonging to families Channidae and Belonidae respectively were examined. A total of 4 digenetic trematode parasites belonging to 4 different families i.e., Euclinostomum heterostomum (Clinostomidae Luhe, 1901); Phyllodistomum tripathi (Gorgoderidae Looss, 1901); Genarchopsis piscicola (Hemiuridae, Luhe, 1901), and Bucephalopsis karvei (Bucephalidae Poche, 1907) were detected. The overall prevalence of digenetic trematode infection was 65.90% and the mean intensity was 3.58. Among these Genarchopsis piscicola showed the highest prevalence (40.38%) with mean intensity 2.95 in the host fish Xenentodon cancila, while in other species the prevalence ranged between 26.23 and 34.62%. Present study authenticates the presence of several species of digenetic trematode parasites in the fish inhabiting freshwaters of J&K union territory.

Traditional Lifestyle of the Indigenous Population of the Khabarovsk Krai as a Factor Determining the Spread of Helminth Infections

Introduction: Supporting health and wellbeing of indigenous small-numbered peoples of the North is one of the priorities of the regional policy in the Khabarovsk Krai. The centuries-long adaptation of the population to local conditions has created a unique system of the traditional use of natural resources and the most efficient forms and types of households. Despite all globalization processes, fishing, hunting and gathering remain essential elements of the lifestyle of northern indigenous peoples. Against the natural background, specific features of their behavior and nutrition create optimal conditions for helminth life cycles and intense transmission of endemic helminth infections. Objective: To assess effects of the traditional lifestyle of the indigenous population of the Khabarovsk Krai as a factor responsible for the spread of larval helminthiasis and endemic trematode infections. Materials and methods: In 2010–2020, questionnaire-based surveys were conducted and feces samples were collected from Nanai people in the villages of Dada, Sikachi-Alyan, Sinda, and Naikhin and from Udege people in the villages of Gvasyugi and Arsenyevo during expeditions. Results: Endemic trematode eggs were detected in stool samples from all the villages. Clonorchis sinensis eggs were detected in the samples from Dada, Sinda, and Sikachi-Alyan, while Nanophyetus salmincola schikhobalowi eggs were found in the dwellers of Arsenyevo and Gvasyugi. Metagonimus spp. eggs were also detected in isolated cases. The results of sero-epidemiological survey indicate a high frequency of contacts with Toxocara roundworms in all areas and with tapeworms of the Echinococcus type in the traditional villages located in forest areas. Conclusion: Original lifestyle and dietary habits of indigenous peoples in the Khabarovsk Krai pose a high risk of trematode infections (clonorchiasis, nanophietiasis, metagonimiasis) and larval helminthiasis (echinococcosis, toxocarosis). In combination with poor awareness of the population of appropriate preventive measures, this risk contributes to high incidence and prevalence rates of helminthiases in all surveyed national villages.

A Note on Filopaludina martensi martensi (Frauenfeld, 1865) Artificial Breeding Conditions

Highlight ResearchLong-term maintenance of Filopaludina martensi martensi in artificial conditions (local tap-water and food).Observation of breeding behaviour of F. m. martensi.Observation of birth and development of the juveniles. AbstractFilopaludina martensi martensi Frauenfeld 1865 is an aquatic Viviparidae gastropod found in Thailand, and throughout Southeast Asia. It is popular in the local cousin, a vector of food-borne trematode infections, and used as a bio-indicator of heavy metal contamination, bio-control agent against Bithynia siamensis Lea 1856, and a way to reduce the total organic matter content from faeces and feed residue during Clarias sp. catfish and Nile tilapia aquaculture. The study aims to establish a protocol for breeding F. m. martensi snails in artificial conditions. The snails were maintained in laboratory conditions. The animals gave birth (3 - 4 juveniles) every month. Inflatable, for several hours after the birth, transparent lightly bluish (5 - 6 mm in diameter) spheres are released in which the fully mature juvenile moves, and leaves several hours later after the sphere breaks. All juveniles studied here die after 2 - 3 months failing to grow into a reproductive adults. F. m. martensi is an attractive animal that regardless of the current difficulties to maintain and grow its juveniles may be popularised in the ornamental fish trade, and a possible laboratory model animal.

A large-scale epidemiological investigation on trematode infections in small ruminants in Bangladesh.

BackgroundThe important trematode species in small ruminants: Paramphistomum sp., Fasciola spp. and Schistosoma spp. seriously affect the productivity of domestic ruminants in endemic areas.MethodsIn the present study, we identified the potential risk factors associated with trematodes infections in small ruminants in seven topographic zones of Bangladesh using simple sedimentation and modified Stoll’ ova counting technique.ResultsA total of 2440 samples were examined, where 965 were found positive with one or more trematode species with an overall prevalence of 39.5% (95% CI, 37.6%–41.5%) and intensity of infection was 264.77 ± 9.86 egg per gram of faeces. Three trematode species were identified namely Paramphistomum sp. (34.1%, 32.2%–36.0%), Fasciola spp. (7.5%, 6.5%–8.6%) and Schistosoma spp. (2.7%, 2.1%–3.5%). Prevalence of co‐infection was 4.8%. The spatial distribution of trematode infections varied from 29.5% to 53.6%. Univariate analysis revealed that physiological condition of females, body condition, farming system, deworming and season were significantly (p < 0.05) associated with trematodes infections in small ruminants. By multiple logistic regression model, three factors such as physiological condition of females (pregnant and lactating), poor body condition and animals without deworming were identified as potential risk factors for trematodes infection in small ruminants.ConclusionTrematode infections are prevalent in the study areas and Paramphistomum sp. is most common in different areas among the identified trematodes species.Government should take necessary action to appraise an effective control strategy of trematode infections in small ruminants.

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.

High prevalence of urinary schistosomiasis in a desert population: results from an exploratory study around the Ounianga lakes in Chad

BackgroundResearching a water-borne disease in the middle of the Sahara desert might not seem the most relevant concern. However, nomadic Sahelian pastoralists health concerns regarding their livestock and anecdotal reports about trematode infections of Fasciola spp. and Schistosoma spp. in desert-raised animals justified an exploratory study focusing on the lakes of Ounianga in Northern Chad. The aim was to test whether trematode parasites such as Schistosoma spp. occur in human populations living around the Sahara desert lakes of Ounianga Kebir and Ounianga Serir in northern Chad.MethodsThe study was carried out in January 2019 and comprised of three components. First, a cross sectional survey based on a random sample drawn from the population to detect infections with S. haematobium and S. mansoni; second, focus group discussions exploring disease priorities, access to health and health seeking behaviour; and third, surveying water contact sites for intermediate host snails. Samples of trematode parasites and snails were confirmed on species level by molecular genetic methods. For parasitological and malacological surveys descriptive statistics were performed. Qualitative data analysis included the full review of all transcripts, followed by a descriptive and explorative thematic analysis.ResultsAmong 258 participants, the overall S. haematobium prevalence using urine filtration was 39.2% [95% confidence interval (CI): 33.5–45.1%], with 51.5% of the infected suffering from heavy infection. The intermediate host snail of S. haematobium (Bulinus truncatus) occurred at water contact sites near both study villages, revealing the potential for local transmission. Although a positive S. mansoni point-of-care circulating cathodic antigen (POC-CCA) test result was obtained from 8.6% (95% CI 5.7–12.8%) of the samples, no intermediate host snails of S. mansoni were found, and the relevance of S. mansoni remains uncertain. Qualitative findings underline the importance of morbidity caused by urinary schistosomiasis, and the lack of access to diagnostics and treatment as a major health concern.ConclusionsThis research revealed a high prevalence of urinary schistosomiasis in the population living around the lakes of Ounianga in the Sahara, a United Nations Educational, Scientific and Cultural Organization (UNESCO) world heritage site in Chad. Despite the high public health importance of the associated morbidity expressed by the population, there is no access to diagnostics and treatment. Further work is needed to develop and test a context-adapted intervention.Graphical

Combined effects of salinity and trematode infections on the filtration capacity, growth and condition of mussels

The blue mussel (Mytilus species complex) is an important ecosystem engineer, and salinity can be a major abiotic driver of mussel functioning in coastal ecosystems. However, little is known about the interactive effects of abiotic drivers and trematode infection. This study investigated the combined effects of salinity and Himasthla elongata and Renicola roscovita metacercarial infections on the filtration capacity, growth, and condition of M. edulis from the Baltic Sea. In a laboratory experiment, groups of infected and uninfected mussels were exposed to a wide range of salinities (6-30, in steps of 3) for 1 mo. Shell growth was found to be positively correlated with salinity and optimal at 18-24 at the end of the experiment, imposed by constraints in shell calcification under lower salinities. Mussel shell growth was not affected by H. elongata infection. While salinity had only a minor effect on tissue dry weight, infected mussels had a significantly lower tissue dry weight than uninfected mussels. Most interestingly, the combination of salinity and trematode infections negatively affected the mussels’ condition indices at lower salinity levels (6 and 9), suggesting that trematode infections are more detrimental to mussels when combined with freshening. A significant positive effect of salinity on mussel filtration was found, with an initial optimum at salinity 18 shifting to 18-24 by the end of the experiment. These findings indicate that salinity and parasite infections act as synergistic stressors for mussels, and enhance the understanding of potential future ecosystem shifts under climate change-induced freshening in coastal waters.

Nematodes and trematodes associated with terrestrial gastropods in Nottingham, England.

A parasitological survey of terrestrial slugs and snails was conducted at popular dog walking locations across the city of Nottingham, with the intensions of finding gastropods infected with parasites of medical (or veterinary) importance such as lungworm (metastrongyloid nematodes) and trematodes. A total of 800 gastropods were collected from 16 sites over a 225 km2 area. The extracted nematodes and trematodes were identified by molecular barcoding. Of the 800 gastropods collected, 227 were infected (172 had nematode infections, 37 had trematode infections and 18 had both nematode and trematode infections). Of the nematode infected gastropods genotyped, seven species were identified, Agfa flexilis, Angiostoma gandavense, Angiostoma margaretae, Cosmocerca longicauda, Phasmarhabditis hermaphrodita, Phasmarhabditis neopapillosa and an unknown Cosmocercidae species. Of the trematode infected gastropods genotyped, four species were identified, Brachylaima arcuate, Brachylaima fuscata, Brachylaima mesostoma and an unknown Plagiorchioidea species. No lungworm species were found within the city of Nottingham. To our knowledge, this study represents the first survey of gastropod-associated nematodes and trematodes in the East midlands of the United Kingdom.