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Swimmers’ itch on: a The legs of 3-year girl 2 weeks after infection, b The leg of adult man 2 weeks after infection, c The forearms of 3-year girl 2 weeks after infection, d The forearms of 3-year girl 4 weeks after infection
Source publication
After numerous reports the local press about the "stinging water" in created on the Dzierżęcinka River-Water Valley reservoir and recognizing in bathers the symptoms of swimmers' itch, environmental study on the presence of bird schistosome larvae in snail hosts was conducted. Snails belonging to Lymnaeidae and Planorbidae were collected at two sit...
Citations
... Some investigations often employ molecular approaches, revealing similar species in neighbouring countries or even in those not sharing borders [28,88]. In general, the studies have consistently identified the prevalent intermediate hosts, specifically the genera Radix and Lymnaea, associated with causative agents such as T. szidati, T. franki, T. regenti, T. physellae (Austria), T. anseri (Iceland), T. mergi (Iceland), and B. polonica, as the primary contributors to CD in Europe [22][23][24]56,89]. The studies identified were not carried out in all European countries, but mainly in central and northern Europe, indicating significant gaps in the evaluation of the full extent of this zoonosis, maybe due to undiagnosed cases masking the true CD prevalence in other countries, such as Portugal. ...
... stagnalis, Radix balthica/labiata, Radix auricularia, and P. corneus) infected with digenic larvae (B. polonica and Trichobilharzia sp.) [89]. In Germany, studies on freshwater areas, such as Lake Baldeney, Ruhr River, and Lake Tunisee, confirmed the presence of T. franki in the latter, emphasizing the need for prior knowledge for preventive measures in recreational waters [21,79,95,96]. ...
... The economic impacts attributed to CD in Europe predominantly affect the tourism sector, particularly with the growing number of individuals engaging in recreational water activities [42,79]. Depending on the level of cercaria infestation in water bodies, certain fluvial beaches may temporarily close as a protective measure until conditions allow for their reopening [89,103]. It is essential to consider the potential occupational risks associated with CD, particularly associated with farming, notably rice fields, where intermediate and vertebrate hosts are present. ...
Cercarial dermatitis (CD), or “Swimmer’s itch” as it is also known, is a waterborne illness caused by a blood fluke from the family Schistosomatidae. It occurs when cercariae of trematode species that do not have humans as their definitive host accidentally penetrate human skin (in an aquatic environment) and trigger allergic symptoms at the site of contact. It is an emerging zoonosis that occurs through water and is often overlooked during differential diagnosis. Some of the factors contributing to the emergence of diseases like CD are related to global warming, which brings about climate change, water eutrophication, the colonization of ponds by snails susceptible to the parasite, and sunlight exposure in the summer, associated with migratory bird routes. Therefore, with the increase in tourism, especially at fluvial beaches, it is relevant to analyze the current epidemiological scenario of CD in European countries and the potential regions at risk.
... Prior studies on schistosomes and other trematode parasites show that their distributions closely match the distributions of their molluscan intermediate hosts (Skírnisson et al., 2004;Dida et al., 2014;Marszewska et al., 2016;Gordy et al., 2018;Soper et al., 2023). Therefore, environmental factors that influence the abundance of intermediate host snails are likely to be major predictors of cercaria abundance (see Fig. 1. for a priori hypothesized relationships; Rohr et al., 2008a;Paull et al., 2015). ...
Avian schistosomes are snail-borne trematode parasites (Trichobilharzia spp.) that can cause a nasty skin rash in humans when their cercariae mistake us for their normal bird hosts. We sought to investigate drivers of the spatial distribution of Trichobilharzia cercaria abundance throughout Northern Michigan lakes. For 38 sites on 16 lakes, we assessed several dozen potential environmental predictors that we hypothesized might have direct or indirect effects on overall cercaria abundance, based on known relationships between abiotic and biotic factors in wetland ecosystems. We included variables quantifying local densities of intermediate hosts, temperature, periphyton growth rates, human land use and hydrology. We also measured daily abundance of schistosome cercariae in the water over a 5-week period, supported by community scientists who collected and preserved filtered water samples for qPCR. The strongest predictor of cercaria abundance was Lymnaea host snail density. Lymnaea density was higher in deeper lakes and at sites with more deciduous tree cover, consistent with their association with cool temperature habitats. Contrary to past studies of human schistosomes, we also found a significant negative relationship between cercaria abundance and submerged aquatic vegetation, possibly due to vegetation blocking cercaria movement from offshore snail beds. If future work shows that these effects are indeed causal, then these results suggest possible new approaches to managing swimmer's itch risk in northern MI lakes, such as modifying tree cover and shallow-water vegetation at local sites.
... In Europe and North America, HCD is considered an emerging and/or re-emerging disease as cases are increasing [7]. Indeed, monitoring of HCD outbreaks in Europe is now the subject of numerous local and international research projects; various researchers have attempted to better understand risk by examination of snails, inspection of birds and cercariometry of water [8][9][10][11][12][13], alongside introduction of environmental DNA surveillance [14]. Whilst the prevalence of schistosomiasis in European birds can reach 38% [6,8], in the UK its present epidemiology is poorly understood [6,7] despite the presence of numerous freshwater bodies that harbour infected snails along major bird migration flyways from Europe [15,16]. ...
Background
Human cercarial dermatitis (HCD) is a clinical disease typically caused by skin-penetrative larvae of avian schistosomes. Its geographical epidemiology is firmly tied with that of infected freshwater intermediate snail hosts. To better understand the current distribution of HCD and its level of nuisance in the UK, we undertook a systematic literature review.
Methods
Following PRIMSA guidelines, PubMed and Scopus databases were searched with keywords “human cercarial dermatitis” OR “swimmer’s itch” AND “United Kingdom”. Articles about imported cases of HCD, or HCD outside the UK, were not formally included.
Results
A total of 30 articles were initially identified. A further two were gained by inspection of all citations. After screening, eight publications were analysed where the location, number of cases and putative avian schistosome species incriminated were tabulated. HCD is mainly found in the south of England, though gaps in evidence and reporting remain across the UK.
Conclusions
Despite its noted recent rise in open water swimmers, published literature on HCD across the UK is sparse; this condition is both overlooked and under-reported. We therefore recommend establishing a national database that raises awareness and encourages self-reporting of this nuisance disease.
Graphical Abstract
... In Europe, it is mostly recorded in lakes largely occupied with aquatic vegetation [181] . Also, expanding riverbeds and dams created good circumstances for this zoonotic parasitosis to emerge [182] . With a similar ecosystem, in the southwest of the United States, dermatitis-causing schistosomes were increasingly reported suggesting the probability of dermatitis outbreaks [183] . ...
... While molluscs infected with digenean trematodes may release large amounts of infectious larvae, cercariae (Marszewska et al., 2016), even the presence of a single infected first intermediate host may pose a risk of disease outbreaks. It is likely that the dilution effect caused by nonnative competitors may be a tool in "outside the box" strategies for molluscborne disease control, but each parasite-host-diluter system requires individual research, interpretation and careful cost-benefit analysis. ...
There is a great need to understand the impact of complex communities on the free-living parasite stages that are part of them. This task becomes more complex as nonnative species emerge, changing existing relationships and shaping new interactions in the community. A relevant question would be: Can the coexistence of nontarget snails with the target hosts contribute to trematodosis control? We used field and experimental approaches to investigate nonnative competitor-induced parasite dilution. During a three-year field study, we investigated digenean infection in Lymnaea stagnalis from eight Polish lakes inhabited or uninhabited by Potamopyrgus antipodarum. Additionally, we verified the presence of digenean infections in the populations of P. antipodarum. Moreover, we conducted an experimental infection of L. stagnalis with miracidia of Trichobilharzia szidati under increasing densities of P. antipodarum and aimed to infect P. antipodarum with them separately. The prevalence of avian schistosomes in lymnaeid snails was significantly higher in uninhabited lakes than in lakes inhabited by P. antipodarum. Our study indicates that waters with a higher density of invaders have a lower prevalence of avian schistosomes in lymnaeid hosts. The results of experimental studies confirmed that the presence of high densities of P. antipodarum reduces the probability of target host infection. Both field and experimental studies rule out the role of P. antipodarum as a source of avian schistosome cercariae. Here, a nonnative species was tested as a diluter, which in practice may be harmful to the local environment. This work is not a call for the introduction of nonnative species; it is intended to be a stimulus for researchers to continue searching for natural enemies of parasites because, as our results show, they exist. Finding natural enemies to the most dangerous species of human and animal parasites that will pose no threat to the local environment could be groundbreaking.
... The snails involved tend to be associated with higher latitudes and are relatively large, which A. The schistosomes and hosts involved fit a familiar pattern (see T. stagnicolae in Figure 1), with the adult worms found in visceral veins of waterfowl, eggs passed in the feces, and snails of the family Lymnaeidae serving as intermediate hosts. Prominent examples are T. stagnicolae in North America [55][56][57][58][59][60][61], T. szidati and T. franki in Europe [17,[62][63][64][65][66][67][68][69][70], and a species long known from cercariae and swimmer's itch outbreaks but only recently described from adult specimens and named T. longicauda in New Zealand [71]. The snails involved tend to be associated with higher latitudes and are relatively large, which may lead to high cercariae production and, therefore, increased likelihood of being involved in swimmer's itch cases. ...
Although most studies of digenetic trematodes of the family Schistosomatidae dwell on representatives causing human schistosomiasis, the majority of the 130 identified species of schistosomes infect birds or non-human mammals. The cercariae of many of these species can cause swimmer’s itch when they penetrate human skin. Recent years have witnessed a dramatic increase in our understanding of schistosome diversity, now encompassing 17 genera with eight more lineages awaiting description. Collectively, schistosomes exploit 16 families of caenogastropod or heterobranch gastropod intermediate hosts. Basal lineages today are found in marine gastropods and birds, but subsequent diversification has largely taken place in freshwater, with some reversions to marine habitats. It seems increasingly likely that schistosomes have on two separate occasions colonized mammals. Swimmer’s itch is a complex zoonotic disease manifested through several different routes of transmission involving a diversity of different host species. Swimmer’s itch also exemplifies the value of adopting the One Health perspective in understanding disease transmission and abundance because the schistosomes involved have complex life cycles that interface with numerous species and abiotic components of their aquatic environments. Given the progress made in revealing their diversity and biology, and the wealth of questions posed by itch-causing schistosomes, they provide excellent models for implementation of long-term interdisciplinary studies focused on issues pertinent to disease ecology, the One Health paradigm, and the impacts of climate change, biological invasions and other environmental perturbations.
... Experimental studies on immunocompetent mammalian models show that the majority of the cercariae die in the skin, although some schistosomula can migrate to the nervous system or lungs (Kolářová, 2007, Horák andKolářová 2011). Consequently, monitoring of cercarial dermatitis outbreaks in Europe is now the subjects of many local and international research projects (Pilz et al., 1995;De Gentile et al., 1996;Kolářová et al., 1999;Thors and Linder 2001;Dubois et al., 2001;Canestri-Trotti et al., 2001;Zbikowska et al., 2001;Fraser et al., 2009;Soldánová et al., 2013;Marszewska et al., 2016;Al-Jubury et al., 2020). It is mostly species belonging to the genus of Trichobilharzia that have been identified as causative agents of outbreaks in Europe. ...
Cercarial dermatitis in humans is a re-emerging zoonotic disease caused by infectious larvae of avian blood flukes within the Schistosomatidae family. Upon water contact, these avian schistosome larvae directly penetrate human skin and cause irritation. Between September 2018 and September 2020, carcasses of 94 mallards (Anas platyrhynchos), two green-winged teals (Anas crecca) along with one ferruginous duck (Aythya nyroca) were examined. Birds were collected within 12 regions of Hungary, representative of 9 different counties. Inspecting both morphological characters and molecular data, the cytochrome oxidase subunit I (COI) and large subunit ribosomal DNA (LSU rDNA) sequences, Bilharziella polonica and Dendritobilharzia pulverulenta were each identified. Most importantly, Trichobilharzia franki was found for the first time in Hungary and in 5 dispersed counties in conjunction with of 3 counties where other avian schistosomes were found. Of note, these avian blood flukes were predominately encountered in wild mallards (∼50%) and not in birds reared for hunting (∼1%). In total, 245 European ear snails (Radix auricularia), a known intermediate host of Trichobilharzia spp., were collected from an urban pond in Eger, Hungary. Five snails (∼2%) consistently shed numerous furcocercariae of T. franki that were confirmed by molecular methods. Our findings help to pinpoint a contemporary life cycle of this avian schistosome within an urban environment, a location regularly visited by various wild waterfowl and the possible species of avian schistosomes responsible for cercarial dermatitis in Hungary. Taken as a whole, we demonstrate the actual and potential risk zone for cercarial dermatitis, particularly with reference to R. auricularia distributions, within Hungary and across Central Europe.
... Furthermore, this mollusk species acts as an intermediate host for zoonotic avian schistosomes in North America [2,11] and recently in Europe [25]. Considering the reduced prevalence rates associated with these parasites (e.g., Horák & Kolářová [6]; Marszewska et al. [8]; Brant & Loker [11]; Al-Jubury et al. [36]), the absence of parasitism by schistosomes in the remaining snail species studied here, such as P. acuta, could be related to the small sample size per area, per snail species (in some cases), or it could even be considered an expected result. However, P. acuta yielded negative results despite its large sample size when compared with C. dombeyana, as there were 1390 versus 714 snails, respectively. ...
... Although there are no data on the zoonotic potential of the latter species, these groups of parasites, with Trichobilharzia 17 egent studied by Horák, Kolářová & Dvořák, 1998 as the model species, are of concern because in experimental murine models, they are capable of migrating to the nervous system, causing severe pathological changes in the peripheral and central nervous system of mammals. These effects can include paralysis and locomotory disfunction, alterations that can be extrapolated to humans [7][8][9]39]. ...
... The current climatic scenario is of concern, highlighting the need for additional research on the early identification of potential zoonotic schistosomes in understudied areas, such as the Neotropics. Furthermore, environmental disturbances related to anthropic activities, such as artificial water bodies and eutrophication, play an additional role in this emergence [5,8,23,41]. This contamination process promotes the excessive growth of aquatic vegetation, which serves as shelter and feeding sites for snails, with subsequent increases in the snail population [5,6], which is what took place at the lagoon Laguna Chica de San Pedro. ...
Avian schistosomes are blood flukes parasitizing aquatic birds and snails, which are responsible for a zoonotic disease known as cercarial dermatitis, a hypersensitive reaction associated to the cutaneous penetration of furcocercariae. Despite its worldwide distribution, its knowledge is fragmentary in the Neotropics, with most of data coming from Argentina and Brazil. In Chile, there are only two mentions of these parasites from birds, and one human outbreak was associated to the genus “Trichobilharzia”. However, the identity of such parasites is pending. The aim of this study was to identify the furcocercariae of avian schistosomes from Southern Chile using an integrative approach. Thus, a total of 2283 freshwater snails from different families were collected from three different regions. All snails were stimulated for the shedding of furcocercariae, but only Chilina dombeyana (Chilinidae) from the Biobío region was found to be parasitized. The morphology and phylogenetic analyses of 28S and COI genes stated two lineages, different from Trichobilharzia, shared with Argentina. This study provides new information on Neotropical schistosomes, highlighting the need for major research on these neglected trematodes, which are considered to be emerging/re-emerging parasites in other parts of the globe as consequence of anthropogenic disturbances and climatic change. Highlights: 1. Two different lineages (Lineage I and II) were described and molecularly characterized (28S and COI genes); 2. Cercaria chilinae I y II are proposed as a synonymous of Lineage II. Thus, a total of four different lineages of avian schistosomes are related to Chilina spp.; 3. Chilina spp. represents an important intermediate host for avian schistosomes in South America, constituting a reservoir de schistosomes with zoonotic potential; 4. Coinfection between the two different lineages was found, a finding previously not reported for avian schistosomes; 5. Expansion in the geographic distribution of Nasusbilharzia melancorhypha from its original record in Argentina, with Chilina dombeyana as an additional intermediate host.
... However, in some cases cercarial infection can also lead to more serious symptoms such as anaphylaxis or disorders of the respiratory system [6]. There have also been reports of other symptoms such as nausea, diarrhea, swollen glands, insomnia, and fever as well as reports of finding schistosomula in different organs of mammals which are summarized in Marszewska et al. and Horák et al. [3,7]. Worldwide, several genera are known to cause these symptoms [3,8]. ...
Several species of avian schistosomes are known to cause dermatitis in humans worldwide. In Europe, this applies above all to species of the genus Trichobilharzia. For Austria, a lot of data are available on cercarial dermatitis and on the occurrence of Trichobilharzia, yet species identification of trematodes in most cases is doubtful due to the challenging morphological determination of cercariae. During a survey of trematodes in freshwater snails, we were able to detect a species in the snail Physella acuta (Draparnaud, 1805) hitherto unknown for Austria, Trichobilharzia physellae; this is also the first time this species has been reported in Europe. Species identification was performed by integrative taxonomy combining morphological investigations with molecular genetic analyses. The results show a very close relationship between the parasite found in Austria and North American specimens (similarity found in CO1 ≥99.57%). Therefore, a recent introduction of T. physellae into Europe can be assumed.
... Moreover, cercariae can also attack accidental hosts, including humans, causing cercarial dermatitis ("swimmer's itch") [2]. Swimmer's itch is an emerging disease involving an intensely itchy rash but also general symptoms such as catarrh, diarrhoea, fever, insomnia [3][4][5] and in extraordinary cases disorders of the respiratory system and even anaphylactic shock [6]. Bird schistosome larvae may overcome the barrier of the mammalian skin and reach the internal organs [7]; more specifically, schistosomulae have been found in the lungs, heart, liver, kidney or intestine [7][8][9]. ...
... Cercarial dermatitis has been reported from nearly all continents, including Europe [11]. There are currently plentiful reports of outbreaks of swimmer's itch from recreational water bodies [5,[12][13][14][15][16]. Scientists are constantly looking for an effective method of protecting bathing areas from rashes of aquatic origin [17][18][19][20][21]. Methods that require human intervention related to the final host include (i.) reducing the population of bird hosts in recreational water areas by translocating these final hosts to other places, scaring them away using pyrotechnic harassment or even culling them and addling their eggs, as well as (ii.) the treatment of waterfowl with the anthelmintic drug praziquantel [22,23]. ...
Research on alien and invasive species focuses on the direct effects of invasion on native ecosystems, and the possible positive effects of their presence are most often overlooked. Our aim was to check the suitability of selected alien species (the snail Physa acuta, the bivalve Dreissena pol-ymorpha, and the gammarid Dikerogammarus villosus) as diluents for infectious bird schistosome cer-cariae-the etiological factor of swimmer's itch. It has been hypothesized that alien species with different feeding habits (scrapers, filterers and predators) that cohabit the aquatic environment with intermediate hosts of the schistosomatid trematodes are capable of feeding on their free-swimming stages-cercariae. In the laboratory conditions used, all experimental animals diluted the cercariae of bird schistosome. The most effective diluents were P. acuta and D. villosus. However, a wide discrepancy in the dilution of the cercariae between replicates was found for gammarids. The obtained results confirm the hypothesis that increased biodiversity, even when alien species are involved, creates the dilution effect of the free-living stages of parasites. Determining the best diluent for bird schistosome cercariae could greatly assist in the development of current bathing areas protection measures against swimmer's itch.
