Search Results (10)

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. Full article

Schistosomiasis is a neglected tropical disease (NTD) caused by blood flukes (Schistosoma spp.). Schistosomatids affect a wide array of vertebrate hosts, including humans. In the present study, multiple species of schistosomatids were identified by isolating schistosomatid cercariae (SC) from naturally infected snails. We also described different biotic and abiotic factors influencing SC infections in snails and reported human cercarial dermatitis (HCD) for the first time in Bangladesh. A total of 22,012 snails of seven species: Lymnaea auricularia, L. luteola, Indoplanorbis exustus, Physa acuta, Viviparus bengalensis, Brotia spp., and Thiara spp., were collected and examined. Among these snails, 581 (2.6%) belonging to five species: L. luteola, L. auricularia, P. acuta, I. exustus, and V. bengalensis, were infected with SC. The rate of infection was the highest for L. luteola (11.1%), followed by L. auricularia (5.3%), and was the lowest for V. bengalensis (0.4%). Prevalence in snails was the highest in September (16.8%), followed by October (9.5%) and November (8.8%), and was the lowest in colder months, such as January (1.8%) and February (2.1%). Infections with schistosomatids were more common in larger snails and snails collected from sunny areas. We confirmed the presence of Schistosoma indicum, S. incognitum, S. nasale, S. spindale, and Trichobilharzia szidati by PCR and sequencing. Through a questionnaire survey, we detected HCD in 214 (53.5%) individuals, and the infection rate was almost equally distributed across all professions. Collectively, the present results suggest that lymnaeid snails are the main vector for Schistosoma spp. prevalent in Bangladesh, and schistosomatids with zoonotic potential are also prevalent. Full article

A novel schistosome from Planorbella snails currently known as avian schistosomatid sp. C (ASC) was recently described as being capable of causing the papules associated with swimmer’s itch. We conducted a paired study with 24 human volunteers, exposing each of their forearms to five drops of water containing cercariae of ASC or Trichobilharzia stagnicolae, and examined the skin for papules 1–3 days later. A mixed effects model showed that only the parasite species significantly affected the number of papules, while prior experimental exposure, swimming history, and swimmer’s itch experience did not. The total number of papules produced by the two species were very different: ASC produced a total of 2 papules from the 298 cercariae used, compared to 49 papules from 160 T. stagnicolae cercariae, a difference factor of more than 43X, which was comparable to the odds ratio of 45.5 computed using the statistical model. A well-known agent of swimmer’s itch, T. stagnicolae, is able to penetrate human skin more frequently than ASC, likely meaning that ASC is only a minor cause of swimmer’s itch where T. stagnicolae is present. We also completed limited experiments that compared the cercarial behavior of the two species in vitro and in situ. A known stimulant of schistosome cercarial penetration, α-linolenic acid, did not stimulate ASC cercariae to initiate penetration-associated behaviors as frequently as T. stagnicolae. However, when placed on esophageal tissue of the known vertebrate host for ASC, Canada goose (Branta canadensis), ASC cercariae were observed penetrating the esophageal epithelium quickly, whereas T. stagnicolae cercariae did not exhibit any penetration behaviors. Full article

The emergence of cercariae from infected mollusks is considered one of the most important adaptive strategies for maintaining the trematode life cycle. Short transmission opportunities of cercariae are often compensated by periodic daily rhythms in the cercarial release. However, there are virtually no data on the cercarial emergence of bird schistosomes from freshwater ecosystems in northern latitudes. We investigated the daily cercarial emergence rhythms of the bird schistosome Trichobilharzia sp. “peregra” from the snail host Radix balthica in a subarctic lake under both natural and laboratory seasonal conditions. We demonstrated a circadian rhythm with the highest emergence during the morning hours, being seasonally independent of the photo- and thermo-period regimes of subarctic summer and autumn, as well as relatively high production of cercariae at low temperatures typical of northern environments. These patterns were consistent under both field and laboratory conditions. While light intensity triggered and prolonged cercarial emergence, the temperature had little effect on cercarial rhythms but regulated seasonal output rates. This suggests an adaptive strategy of bird schistosomes to compensate for the narrow transmission window. Our results fill a gap in our knowledge of the transmission dynamics and success of bird schistosomes under high latitude conditions that may serve as a basis for elucidating future potential risks and implementing control measures related to the spread of cercarial dermatitis due to global warming. Full article

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. Full article

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. Full article

Schistosomiasis is a helminthic infection and one of the neglected tropical diseases (NTDs). It is caused by blood flukes of the genus Schistosoma. It is an important public health problem, particularly in poverty-stricken areas, especially those within the tropics and subtropics. It is estimated that at least 236 million people worldwide are infected, 90% of them in sub-Saharan Africa, and that this disease causes approximately 300,000 deaths annually. The clinical manifestations are varied and affect practically all organs. There are substantial differences in the clinical presentation, depending on the phase and clinical form of schistosomiasis in which it occurs. Schistosomiasis can remain undiagnosed for a long period of time, with secondary clinical lesion. Here, we review the clinical profile of schistosomiasis. This information may aid in the development of more efficacious treatments and improved disease prognosis. Full article

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. Full article

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 polymorpha, and the gammarid Dikerogammarus villosus) as diluents for infectious bird schistosome cercariae—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. Full article

Cercarial dermatitis, or Swimmer’s itch, is one of the emerging diseases caused by the cercariae of water-borne schistosomes, mainly Trichobilharzia spp. Since the zoonotic potential of Allobilharzia visceralis is still unknown, studies on this schistosome would be helpful to add knowledge on its possible role in causing human infections. In the present study, 54 whooper swans (Cygnus cygnus) from rescue/rehabilitation centers in Honshu, Japan, were necropsied to identify the cause of death. Grossly, 33 (61.11%) swans were severely emaciated and 23 (42.59%) had multiple reddened areas throughout the length of the intestine with no worms detected in the internal organs. Microscopically, adult schistosomes were found in the lumen of the mesenteric, serosal, portal, and testicular veins, in the capillaries of the intestinal lamina propria, and in the sinusoids of the adrenal gland, spleen, and liver of 23 (42.59%) swans. Hypertrophy of veins containing adult worms was identified in 15 (27.77%) swans, and vascular lumen obliteration was observed in 8 (14.81%) swans. Mild to severe villous atrophy and superficial enteritis were observed in 8 birds (14.81%), whereas bile pigments and hemosiderin were detected in the livers of 14 (25.92%) and 18 (33.33%) swans, respectively. In three swans (5.55%), schistosome parasites were found in the subcapsular veins of the testes. The schistosomes in the present study were assumed to be A. visceralis based on the microscopical and histological evidence of adult schistosomes found in the lumen of veins as well as the infection pathology, which was very similar to the schistosome-induced pathology previously reported in swans infected by A. visceralis in Europe and Australia. The swans examined herein most likely died from obstructive phlebitis associated with A. visceralis, but further molecular confirmation is required for identification of this species. However, the present study does not provide new data on the zoonotic potential, but only on the pathogenic potential of this schistosome in swans. Furthermore, our study provides a novel contribution to the description of the pathological effects of avian schistosomes infection in whooper swans in Japan. Full article