Cercarial dermatitis and lake eutrophication in south-central Chile

Cercarial dermatitis is caused by exposure to the cercariae of schistosome species which have birds or mammals as their definitive hosts. A public alarm was raised in the summer of 2004 when this parasitic disease was observed for the first time in south-central Chile at Laguna Chica de San Pedro (36 degrees 51' S, 73 degrees 05' W). Swimmers at this eutrophic lake were surveyed in order to estimate the amount of cercarial dermatitis in the area; participants were observed during the summers of 2004 and 2005 for clinical signs of cercarial dermatitis and 25 Chilina dombeyana snails were collected monthly from Laguna Chica de San Pedro during one year and then examined for animal schistosome cercariae. We found that 3% of the swimmers had pruritic maculopapular rashes on their legs, arms, necks, or other body parts and that between 9.1% (May 2006) and 52.4% (November 2004) of the snails examined were infected with the bird schistosome cercariae Trichobilharzia sp.     

A study on cercarial dermatitis in Khuzestan province, south western Iran

Background

Cercarial dermatitis' or swimmer's itch' is an itchy inflammatory response to the penetration of the skin by non-human schistosome parasites. In the hot season, (May to September) in Khuzestan province in the south west of Iran, swimming in canals and agriculture activities in swampy areas are common. This survey was made on people from villages north of Ahwaz city in south west Iran, to estimate cercarial dermatitis in this region.

Methods

2000 people were observed for clinical signs of cercarial dermatitis. Also 2000 Lymnaea gedrosiana snails were collected from agriculture canals and examined for animal schistosome cercariae during 1998–2000.

Results

From this survey 1.1% of people had pruritic maculopapular rash on their feet, hands or other parts of body. From the total of examined snails, 2.4% were found to be infected with bird schistosome cercariae including Trichobilharzia species.

Conclusion

Cercarial dermatitis could be a health problem in this area. This is the first report of cercarial dermatitis from this region of Iran.     

Cercarial Dermatitis

Cercarial dermatitis or “swimmers’ itch” is a maculopapular skin eruption associated with the penetration of the skin by cercaria of certain species of nonhuman schistosomes. It is globally distributed and affects those who work or play in fresh and salt water.

The etiology and epidemiology of the disease are similar to that of human schistosomiasis (bilharziasis). The trematode parasite passes through a life cycle that involves both warm-blooded and molluscan hosts.

The clinical manifestations of “swimmers’ itch” are principally associated with an intensely pruritic dermatitis that lasts five to ten days and becomes more severe with subsequent exposure. Prevention is directed toward control of the molluscan hosts and their supporting environment. Treatment is symptomatic.     

Electrophoretic studies of planorbid egg-proteins: The Bulinus africanus and B. forskalii species groups*

It is possible that physiological differences between populations of an intermediate snail host of schistosomes may be linked with differences in the pathogenicity of the parasite strains they harbour. With a view to differentiating between local populations of bulinid snails, a previous electrophoretic study of snail egg-proteins has been extended to cover all the recognized species of the Bulinus africanus group and most of those of the B. forskalii group.     

Species Identification of Birds Nasal Trichobilharzia in Sari,North of Iran

Background

Cercarial dermatitis is known as an endemic parasitic disease in North of Iran, a hypersensitive skin reaction to the penetration of nonhuman schistosome larvae into human skin. In recent studies in this region, final and intermediate hosts were recognized and Trichobilharzia was identified as the main causative agent of cercarial dermatitis in this region, but to date the parasite species haven''t been identified. Therefore this study was performed to species identification of nasal Trichobilharzia in infected birds for the first time.

Methods

A total of 45 Anas clypeata birds identified as final host, were collected from Sari in North of Iran and infected nasal tissues analyzed using molecular techniques. Genomic DNA was isolated by phenol/chloroform extraction method and ITS region of rDNA were amplified with specific primers its5Trem and its4Trem, then sequenced area were compared with existing records in GenBank.

Results

Twelve samples were infected with Trichobilharzia and results of PCR reaction indicated that all of them belonged to T. regenti. The sequence alignment of present work isolates and those deposited in GenBank showed differences in nucleotide sequences of repeat region in ITS1.

Conclusion

Trichobilharzia regenti is the most frequent parasite of Anatid birds in North of Iran. This corresponds to the distribution of this parasite along the flyway of migratory birds, which annually migrate from Siberia and northern countries of Caspian Sea to wintering areas in southern regions of it.     

La dermatite cercarienne en Europe: un problème de santé publique nouveau?

Cercarial dermatitis is a parasitic impasse that has worldwide distribution. The condition manifests itself as a highly pruriginous skin rash and is due to penetration of the dermis by larval stages (furcocercariae) of avian trematodes. Many species may be responsible for this disease. In Europe the genus Trichobilharzia is widely represented, in particular by the species T. ocellata; the definitive host is the duck (Anas platyrhinchos); the intermediate hosts are snails of the genus Lymnea (L. ovata or L. stagnalis). In France, cases of cercarial dermatitis were reported in June and July 1994 to the health authorities of three départements in the Pays de la Loire Region (western France). The epidemiological situation, common to the three maintained ponds that were concerned, is as follows: high level of eutrophication of the sites, colonization of the ponds by L. ovata, and settlement by many duck colonies. The simultaneous occurrence of these three phenomena, combined with long hours of sunshine in the summer, is responsible for most of the foci of cercarial dermatitis recently described in Europe. Control of this condition is difficult, requiring strict maintenance of bodies of water and if necessary the use of molluscicides such as niclosamide. The use of praziquantel in baits for treating the definitive hosts appears to interrupt the natural cycle of the avian Schistosomatidae. In the light of the observations reported here and the analysis of recent publications, cercarial dermatitis may be regarded as an emerging disease. Its public health impact needs to be evaluated at the global level.     

Trace element and organochlorine concentrations in California clapper rail (Rallus longirostris obsoletus) eggs

Trace contaminant concentrations were measured in eggs of endangered California clapper rails (Rallus longirostris obsoletus) collected from San Francisco Bay during 1975, 1986, and 1987, and in clapper rail eggs (R. l. waynei) from North Carolina during 1987. Residues of 10 detected organochlorines (OC) were low and decreased by 2 to 3-fold from 1975 to 1986–1987 for San Francisco Bay samples, whereas eggshell thickness remained unchanged and comparable to eggs collected prior to 1940. Mercury (Hg) concentrations in eggs from San Francisco Bay were higher than those from North Carolina, and comparable to concentrations associated with reproductive effects in other avian species. Selenium (Se) concentrations in eggs from San Francisco Bay were also higher than those from North Carolina, and were highest in a north San Francisco Bay marsh adjacent to an oil refinery. Individual Se concentrations were slightly lower than values associated with embryotoxicity in other rallids. We recommend additional research on the effects of these and other contaminants on California clapper rails and the restoration of rail habitat.     

Population genetics of African Schistosoma species

Blood flukes within the genus Schistosoma (schistosomes) are responsible for the major disease, schistosomiasis, in tropical and sub-tropical areas. This disease is predominantly present on the African continent with more than 85% of the human cases. Schistosomes are also parasites of veterinary importance infecting livestock and wildlife. Schistosoma population genetic structure and diversity are important characteristics that may reflect variations in selection pressures such as those induced by host (mammalian and snail) environments, habitat change, migration and also treatment/control interventions, all of which also shape speciation and evolution of the whole Schistosoma genus. Investigations into schistosome population genetic structure, diversity and evolution has been an area of important debate and research. Supported by advances in molecular techniques with capabilities for multi-locus genetic analyses for single larvae schistosome genetic investigations have greatly progressed in the last decade. This paper aims to review the genetic studies of both animal and human infecting schistosome. Population genetic structures are reviewed at different spatial scales: local, regional or continental (i.e. phylogeography). Within species genetic diversities are discussed compared and the compounding factors discussed, including the effect of mass drug administration. Finally, the ability for intra-species hybridisation questions species integrities and poses many questions in relation to the natural epidemiology of co-endemic species. Here we review molecularly confirmed hybridisation events (in relation to human disease) and discuss the possible impact for ongoing and future control and elimination.     

Investigation of an outbreak of cercarial dermatitis

We present the investigation of an outbreak of cercarial dermatitis that occurred in a recreational-tourist lake in the Quebec City region (Canada) in the summer of 1999. A case-reporting form was sent to 450 families likely to have activities that would bring them in contact with the lake's water. The snails were characterized and the prevalence of their infestation by schistosomes was investigated. In total, 63 episodes consistent with cercarial dermatitis were reported. Sixty-nine percent of the cases occurred from swimming at the same beach. This location was the one where the only population of snails in the lake was identified. Shoreline residents were informed that they should not feed waterfowl, and a clean-up of the snail population was done at the start of the following summer. There were no cases of cercarial dermatitis at this site the following summer.     

The species of the genus Bulinus, intermediate hosts of Schistosoma

The conditions of snail life in African inland waters favour the evolution of microgeographical races while hindering the formation of new species, and the distinctions between many of the bulinid intermediate hosts of Schistosoma are consequently blurred. In this paper the author comments on the distinguishing characters that have been established for the known Bulinus species and subspecies and summarizes the present knowledge of their distribution and importance as intermediate hosts. His work is based on the examination of over 1540 snail samples received at the WHO Snail Identification Centre in Charlottenlund, Denmark.     

Seasonal and Geographic Distribution of Cercarial Infection in Lymnaea gedrosiana (Pulmunata: Lymnaeidae) In North West Iran

Background

Trematodes are a diverse group of endoparasites which require molluscan and vertebrate animals as intermediate and definitive hosts in their life cycle. The present study was carried out to determine the diversity and geographic distribution of infection with trematodes''cercariae in the snail Lymnaea gedrosiana from north-west Iran.

Methods

A total number of 6759 Lymnaeidae snails were collected from 28 snail habitats; of these L. gedrosiana was the prevalent snail (74.37%) which examined for cercarial infection by shedding method.

Results

The overall infection rate was 8.03%. The most frequent trematodes cercariae in the snail were xiphidiocercariae (81.98%), furcocercariae (32.26%), echinostome cercariae (5.19%), and monostome cercariae (1.24%). The highest infection rate in L. gedrosiana (100%) was with echinostome cercariae from Golestaneh in autumn.

Conclusion

Due to the important role of pond snails in transmission of cercariae to fish as a source of zoonotic diseases, it is essential to estimate the distribution and abundance of the snails and the rate of their infection with different trematodes’ cercariae, and establish control programs in each region.     

Development and Effects of Schistosoma japonicum (Trematoda) on its Intermediate Host,Oncomelania hupensis (Gastropoda)

Background

Trematodes belonging to the genus Schistosoma cause schistosomiasis. The relationship between schistosomes and their intermediate hosts varies among snails. This study investigated the effects of S. japonicum on its snail host, Oncomelania hupensis, and cercarial release rythmicity of S. japonicum and the effects of light on it.

Methods

Seven groups of O. hupensis (n = 40 each) were exposed individually to 0 (control), 2, 4, 6, 10, 15, and 20 S. japonicum miracidia. Mortality of the snails was recorded for 10 weeks. Snails in each group were checked for infection at seven weeks post-exposure. Positive snails were exposed to artificial light from 06:00 am – 18:00 pm and the liberated cercariae were collected every 2 hours to determine the rhythmicity of cercarial release. Three groups of positive snails (n = 6 each) were exposed to artificial light, daylight, and darkness from 06:00 am – 18:00 pm, the liberated cercariae were collected every 2 hours to determine the effects of light.

Results

The highest infection rate and host mortality occurred among snails in the groups exposed to 15 and 20 miracidia. Cercariae were liberated after eight weeks of exposure of O. hupensis to S. japonicum. The circarial emerging pattern was circadian, with a single peak of emerging between 10:00 am and 12:00 pm. Light intensity had a positive influence on cercariae shedding and rhythmicity.

Conclusion

Further research, including the influence of biotic and abiotic factors is deemed necessary to fine-tune elucidation of the effects of S. japonicum upon O. hupensis snail.     

How Many Transgender Men Are There in San Francisco?

The purpose of this study was to estimate the number of transgender men (transmen) adults living in San Francisco. We integrated two population size estimation methods into a community-based health survey of transmen (n = 122) in the San Francisco Bay Area in 2014–2015: the service multiplier and wisdom of the crowds. The median estimate was 806 transmen adults in San Francisco (0.11% of adults) and 4027 in the Bay Area. Considering potential biases, we believe our estimates are conservative. Knowing the denominator of persons at risk for health conditions is necessary for public health planning, surveillance, and impact evaluation.     

Spatial and temporal variations in silver contamination and toxicity in San Francisco Bay

Although San Francisco Bay has a "Golden Gate", it may be argued that it is the "Silver Estuary". For at one time the Bay was reported to have the highest levels of silver in its sediments and biota, along with the only accurately measured values of silver in solution, of any estuarine system. Since then others have argued that silver contamination is higher elsewhere (e.g., New York Bight, Florida Bay, Galveston Bay) in a peculiar form of pollution machismo, while silver contamination has measurably declined in sediments, biota, and surface waters of the Bay over the past two to three decades. Documentation of those systemic temporal declines has been possible because of long-term, ongoing monitoring programs, using rigorous trace metal clean sampling and analytical techniques, of the United States Geological Survey and San Francisco Bay Regional Monitoring Program that are summarized in this report. However, recent toxicity studies with macro-invertebrates in the Bay have indicated that silver may still be adversely affecting the health of the estuarine system, and other studies have indicated that silver concentrations in the Bay may be increasing due to new industrial inputs and/or the diagenetic remobilization of silver from historically contaminated sediments being re-exposed to overlying surface waters and benthos. Consequently, the Bay may not be ready to relinquish its title as the "Silver Estuary".     

Haemolymph Components of Infected & None Infected Lymnaea snails with Xiphidiocercariae

Background

In this study the haemolymph components of infected and none infected Lymnaea gedrosiana with xiphidiocercaria larvae was compared.

Methods

Five hundred Fifty Lymnaea snails were collected from Ilam and Mazandaran provinces, Iran, during 2008–2009. The snails were transported to the lab at Tehran University of Medical Sciences and their cercarial sheddings were studied. Haemolmyphs of snails were extracted and cells were counted using haemocytometer and cell-surface carbohydrate were recognized by conjugated lectin (Lentil). Haemolymph protein concentrations were measured by Bradford protein assay method and soluble protein compositions were determined on sodium dodecyl sulphate polyacrilamide gel electrophoresis (SDS-PAGE).

Results

From the 550 examined Lymnaea snails for cercariae, 27 snails were infected with xiphidiocercariae. Mean of haemolymph cells (haemocyte) number were obtained 93480±2.43 (cells/ml) for none infected snails (25 snail) and 124560±2800 (cells/ml) for infected snails (25 snail). Mannose carbohydrate was recognized on haemocyte of none infected and infected snails. Mean of protein concentration of haemolymph plasma was obtained as 1354±160 µg/ml (1.4 mg/ml) for none infected snails (25 snails) and 1802±138 µg/ml (1.8 mg/ml) for infected snail (25 snails). Comparing to none infected snails, the SDS-PAGE results of haemolymph plasma of infected snails, showed an extra protein band (70 kDa). The results showed a significant difference between the amounts and the kinds of proteins in haemolymph of infected and none infected snails.

Conclusion

This information might be useful to understand of parasite detection, adhesion, engulfment and antigen agglutination by snail.     

New insights into the transmission biology of urinary schistosomiasis in Zanzibar

A better understanding of the transmission biology of urinary schistosomiasis in Zanzibar, Tanzania was only possible after the development of molecular DNA markers for identification of Bulinus africanus group snails, the potential intermediate hosts of Schistosoma haematobium. Hitherto, identification of natural populations of B. globosus and B. nasutus was problematic and the intermediate host status and distribution of either species remained speculative. By recourse to molecular markers, snail distribution maps could be drawn, revealing an allopatric distribution and, more importantly, leading to the discovery that B. nasutus played no role in transmission. Indeed, in Unguja the area of active transmission of S. haematobium to humans is confined within the distribution of B. globosus. This strong relationship may prove useful for predicting the distribution of urinary schistosomiasis within Zanzibar and, if snail schistosome compatibilities persist, in other areas nearby, e.g. coastal Tanzania and Kenya. The transmission biology of urinary schistosomiasis in Zanzibar is reviewed, the paper reports on ongoing malacological studies in Zanzibar and Kenya and finally closes by posing the question whether medical malacology forms an essential component associated with mass-scale chemotherapy control programmes.     

Trichobilharzia anseri n. sp. (Schistosomatidae: Digenea), a new visceral species of avian schistosomes isolated from greylag goose (Anser anser L.) in Iceland and France

Parasitological investigations carried out on birds in Iceland and France highlight the presence of four species of avian schistosomes from greylag geese (Anser anser L.): the european nasal species Trichobilharzia regenti and three visceral species, among which an unknown species isolated from blood vessels of the large intestine and liver. Morphological and molecular analyzes of different parasite stages (eggs, adults) revealed new species of Trichobilharzia genus – Trichobilharzia anseri sp. nov. Studies on host–parasite relationship under natural conditions, showed that the life-cycle includes the snail Radix balthica (syn. R. peregra) as intermediate host. The cercariae, already isolated in Iceland from two ponds of the Reykjavik capital area – the Family park and Tjörnin Lake – are the same as those isolated in 1999 by Kolářová et al. during the first study on Icelandic parasitic agents of cercarial dermatitis.     

Electrophoretic studies of some planorbid egg proteins

Morphological characters alone have so far failed to provide adequate criteria for the identification of the molluscan intermediate hosts of African schistosomes. In the course of investigations into various other taxonomic approaches, it has been found that the egg proteins, when subjected to electrophoresis, are sensitive indicators of differences at the population level. About 80 populations of various species of African and Neotropical planorbids have been examined in this preliminary study. Differences at the population level have a considerable bearing on relationships between the snails and the larval schistosomes that parasitize them and help to explain the evolution of local races of schistosomes.     

Toxicity evaluation of bayluscide® and malathion to three developmental stages of freshwater snails

Laboratory studies were conducted to assess the conditions under which the use of malathion in ricelands of Cameroon may impact the transmission of schistosomiasis.Helisoma trivolvis andBiomphalaria havanensis were selected as test organisms due to the lack of intermediate snail hosts in the U.S. Using Bayluscide^® as a reference molluscicidal compound, malathion was tested against snail eggs, juveniles, and adults. Snail eggs were more susceptible to Bayluscide^® and malathion than juvenile snails which in turn were more susceptible than adult snails. A Bayluscide^® concentration of 0.200 mg/L caused 100% mortality to adults of both snail species after 24 h exposure. This relatively high toxicity of Bayluscide^® to freshwater snails is one of the reasons why it has been recommended by the World Health Organization as the molluscicide of choice for control of schistosome-bearing snails. The concentrations of malathion resulting in 100% kill of adult snails after 24 h exposure were 1,200 mg/L forH. trivolvis and 500 mg/L forB. havanensis. After 48 h exposure, these concentrations were reduced to 500 mg/L and 300 mg/L, respectively. Therefore it is expected that the use of malathion for insect control in ricelands of Cameroon may affect the survival of freshwater snails including the intermediate hosts of bilharziasis.     

Human infections with Angiostrongylus cantonensis

Angiostrongylus cantonensis is a parasite that causes eosinophilic meningitis and has been reported to be present on most Pacific islands. Rats are the principal host and several species of land snails the intermediate host. Important paratenic hosts are fresh water shrimp and fish. Modes of transmission include ingestion by man of raw fish, snails and fresh leafy vegetables contaminated by snail slime trails containing larvae. The parasitic worms are neurotropic in man, and the diagnosis should be considered in any adult or child, who presents, in endemic areas or areas with suitable intermediate hosts, with severe unrelenting headache, paresthesias, or a cranial nerve palsy. Eosinophils in the cerebral spinal fluid suggest the diagnosis. Simple analgesia is sufficient for mild cases. Treatment of those with severe symptoms remains controversial. Glucocorticoids, lumbar puncture to reduce intercranial pressure and antihelminthic agents have been used.