Molecular identification of Tricula spp. and the parasitized trematode cercariae in schistosomiasis-endemic areas of Yunnan Province / 中国血吸虫病防治杂志

Objective To characterize a species of the genus Tricula and parasitized trematodes in schistosomiasis-endemic areas of Yunnan Province using a molecular analysis, so as to understand their taxonomic positions. Methods Tricula spp. and Oncomelania snails were collected from Xiangyun County, Yunnan Province, and cercaria parasitizing snails were observed using crushing followed by microscopy. Cercaria parasitizing Tricula snails at various morphologies were sampled using a shedding method. Genomic DNA was extracted from snail soft tissues and cercariae, and the 16S rRNA, COI, 28S rDNA genes in snails and the ND1 and 28S rDNA genes in cercariae were amplified using a PCR assay and sequenced. The species of Tricula snails and their parasitized trematodes was characterized using sequence alignment and phylogenetic analysis. Results Among 382 Tricula snails detected, there were three types of trematode cercariae found, including the non-forked (20.94%, 80/382), double-forked (3.40%, 13/382) and swallow shapes (7.07%, 27/382). Sequence and phylogenetic analyses showed that the 16S rRNA, COI and 28S rDNA gene sequences of this species of Tricula had high homology to those in Delavaya dianchiensis, and were clustered in a branch. Sequencing analysis of the ND1 and 28S rDNA genes revealed that the non-forked cercariae belonged to the family Pleu- rogenidae, the swallow-shaped cercariae belonged to the family Opecoelidae, and the double-forked cercariae belonged to another species of the genus Schistosoma that was different from S. sinensium and S. ovuncatum. Conclusion The species and taxonomy of Triculla spp. and their parasitized trematodes are preliminarily determined in schistosomiasis-endemic areas of Yunnan Province; however, further studies are required to investigate the more definite taxonomy and pathogenicity.

Xiphidiocercariae from naturally infected Lymnaea columella (Mollusca, Gastropoda) in urban area: morphology and ultrastructure of the larvae and histological changes in the mollusc host / Xifidiocercárias obtidas em Lymnaea columella (Mollusca, Gastropoda) naturalmente infectadas em área urbana: morfologia e ultraestrutura da larva e alterações histológicas do molusco hospedeiro

Abstract Urban agriculture is very common in the cities, as Rio de Janeiro and adjacencies, being important as economic activity. However, this practice can create appropriate conditions for establishment and maintenance of life cycle of many parasites. Lymneid snails can act as intermediate hosts of many trematodes species, including those that infect humans and wild and domestic. In the present study, the snail Lymnaea columella was collected from an urban watercress plantations and the morphology of cercariae released by them was analyzed by light and scanning electron microscopy. The specimens were identified as xiphidiocercariae, belonging to the Cercariae Ornatae group, of the order Plagiorchiiformes. Histological examination of the digestive gland of the infected snails revealed the presence of developing sporocysts, with hemocitary infiltration and metaplasia in the epithelial tissue.

Resumo Agricultura urbana é muito comum nas cidades, como Rio de Janeiro e adjacências, sendo uma importante atividade econômica de subsistência. No entanto, esta prática pode criar condições adequadas para o estabelecimento e manutenção do ciclo de vida de muitos parasitos. Os moluscos limneídeos podem atuar como hospedeiros intermédios de muitas espécies de trematódeos, incluindo aqueles que infectam humanos e animais selvagens e domésticos. No presente estudo, o molusco Lymnaea columella foi coletado de plantações urbanas de agrião e a morfologia das cercárias liberadas por eles foi analisada por microscopia eletrônica de varredura leve e de varredura. As larvas foram identificadas como xifidiocercárias, pertencentes ao grupo das Cercariae Ornatae, Ordem Plagiorchiiformes. Análises histológicas da glândula digestiva dos moluscos infectados evidenciaram esporocistos, com formação de granuloma e metaplasia do tecido epitelial.

Human Contamination and Schistosome Infection Intensity in Bulinid and Planorbid Snail Vectors in Kadawa Irrigation Area, Kano State, Nigeria

Objectives of the Study:An Epidemiological Research, a cross-sectional study, was conducted to determine the magnitude of human contamination of irrigation canal perimeter as it relates to the prevalence and intensity of schistosome cercarial infection in snail vectors.Place and Duration of Study:The study was conducted along water canal located within an irrigation area, Kano River Project Phase I, Kadawa, between January and June, 2012.Methodology:The study area was categorized into Zone of Heavy Contamination (ZHC), Zoneof Light Contamination (ZLC) and Zone of Free Contamination (ZFC) based on the density of faecal lumps observed along the canal perimeter using 1m2quadrat sampling technique. Snail vectors of schistosomiasis were collected from these zones, identified and subjected to cercarial shedding. Brevifurcate apharyngeate cercariae were identified as schistosome cercariae.Results:Of the 827 snails collected 28.54% shed schistosome cercariae. The breakdown of infection prevalence was 31.37%, 27.69% and 26.26% for ZHC, ZLC and ZFC respectively. Three snail species recovered in the study area, Bulinus globosus, B. rohlfsi and Biomphalaria pfeifferi had infection intensity of 8.6, 5.67 and 3.94 respectively, with total mean intensity of 4.67. A Chi-squared analysis did not show any significant difference in infection prevalence in the three zones (χ2cal.0.025, χ22, 0.05= 5.99). However, infection intensity was significantly different in the three zones and among the three snail species using analysis of variance (P<0.05). Conclusion:Human environmental contamination with faeces and urine around irrigation canals remains the source of infection to snail hosts and then to humans. It is presumed that contact control through avoidance of defaecation in the open and building of pit latrines near water contact points along irrigation canals will be effective means of drawing a barrier to infection with schistosomes in the study area

Molecular Method vs. Traditional Methods for Estimating the Prevalence of Larval Trematode Infections in Some Red Sea Snails

Peat reserves of the Russian Federation are estimated at more than 170.0 billion tons, it makes more than one-third of theworld resources. The use of peat as a component for the preparation of composts is an important factor in increasing theproductivity of agricultural ecosystems. During two cycles of four-course crop rotation ‘potatoes – barley – annual grasses– winter wheat’, we studied the influence of lowland peat, composted peat-poultry manure, cattle manure, their combinedapplication with mineral fertilizers on soil physicochemical properties, nitrifying and cellulosolytic activity of soil andproductivity of crop rotation. Application of cattle manure and composted peat-poultry manure contributes to the increase inthe content of humus in soil by 0.07-0.16%, when combined with mineral fertilizers – by 0.14-0.22%, respectively. Onaverage, the highest yield was noted in the variants with cattle manure and composted peat-poultry manure – 10.75-12.13 tha -1 of grain units (g.u.), while in the check (without fertilizers) it was 8.03 g.u. (t ha -1). That is why peat is more profitableto use in the form of composts, especially as a component of composted peat-poultry manure

Study on rapid recognition technique of schistosome susceptibility water bodyⅠAnimal skin making and effect assessment / 中国血吸虫病防治杂志

Objective To develop a bionic animal skin and evaluate its detective effect of Schistosoma japonicum cercariae so as to provide a new technique for the monitoring of the schistosome susceptibility water body.Methods A bionic animal skin was made with pigskin and the experiments were carried out for evaluating its detective effects of S.japonicum cercariae in labo-ratory and simulate fields,and at the same time,the sentinel mouse method was used as the control.Results In the laborato-ry,the cercariae were found in 10-,30-,60-cercaria subgroups in the bionic animal skin group after 1 and 2 hours,but the cer-cariae were found only in the 60-cercaria subgroup in the sentinel mouse group.In the simulate fields,in the water body with 5 schistosome-infected Oncomelania hupensis snails,the cercariae were found in 2 bionic animal skin devices(2/4)and 3 bionic animal skin devices(3/4)after 2 hours and 4 hours respectively,and in the water body with 10 schistosome-infected O.hupensis snails,the cercariae were found in 4 bionic animal skin devices(4/4)and 3 bionic animal skin devices(3/4)after 2 hours and 4 hours respectively in the bionic animal skin group.In the the sentinel mouse group,in the above-mentioned water bodies(with 5 or 10 schistosome-infected O.hupensis snails),the cercariae were found in 2 sentinel mice(2/4)and 1 sentinel mice(1/4)af-ter 2 hours and 4 hours respectively;and the cercariae were found in 2 sentinel mice(2/4)and 3 sentinel mice(3/4)after 2 hours and 4 hours respectively.Conclusion The bionic animal skin device can be used to detect the S.japonicum cercariae, and its sensibility and efficiency are superior to the traditional sentinel mouse method.

Freshwater Snail Diversity in Mae Lao Agricultural Basin (Chiang Rai, Thailand) with a Focus on Larval Trematode Infections

The aim of this study was to conduct a freshwater snail survey in Mae Lao agricultural basin to assess the diversity with a focus on habitat types and their larval trematode infections. Snails were collected and examined in 14 sites of Mae Lao agricultural basin from August 2016 to October 2017. A total of 1,688 snail individuals were collected and classified into 7 families, 8 genera, and 12 species. Snail diversity and habitat types were higher in rice paddies than irrigation canals and streams. The most abundant species was Bithynia siamensis siamensis, representing 54.6% of the sample. Three species of snails act as first intermediate host were found with cercarial infections. They were Filopaludina sumatrensis polygramma, B. s. siamensis, and Melanoides tuberculata. The cercariae were categorized into 7 types; echinostome, monostome, gymnocephalous, virgulate, parapleurolophocercous, pleurolophocercous and megalurous cercariae. Parapleurolophocercous cercariae constituted the most common type of cercariae recovered, contributing 41.2% of all infections in snails. Echinostome metacercariae infections were found in 6 snail species with 7.6% prevalence. In addition, the metacercaria of avian trematode, Thapariella sp. were found in Filopaludina spp. snails and B. funiculata with a prevalence of 0.5%. This is the first report for Thapariella metacercariae in the snail host, B. funiculata, and also confirmed that viviparid and bithyniid snails act as the second intermediate hosts of this trematode. This work will provide new information on the distribution and intermediate host of trematode in this area.

Xiphidiocercariae from naturally infected Lymnaea columella (Mollusca, Gastropoda) in urban area: morphology and ultrastructure of the larvae and histological changes in the mollusc host

Abstract Urban agriculture is very common in the cities, as Rio de Janeiro and adjacencies, being important as economic activity. However, this practice can create appropriate conditions for establishment and maintenance of life cycle of many parasites. Lymneid snails can act as intermediate hosts of many trematodes species, including those that infect humans and wild and domestic. In the present study, the snail Lymnaea columella was collected from an urban watercress plantations and the morphology of cercariae released by them was analyzed by light and scanning electron microscopy. The specimens were identified as xiphidiocercariae, belonging to the Cercariae Ornatae group, of the order Plagiorchiiformes. Histological examination of the digestive gland of the infected snails revealed the presence of developing sporocysts, with hemocitary infiltration and metaplasia in the epithelial tissue.

Resumo Agricultura urbana é muito comum nas cidades, como Rio de Janeiro e adjacências, sendo uma importante atividade econômica de subsistência. No entanto, esta prática pode criar condições adequadas para o estabelecimento e manutenção do ciclo de vida de muitos parasitos. Os moluscos limneídeos podem atuar como hospedeiros intermédios de muitas espécies de trematódeos, incluindo aqueles que infectam humanos e animais selvagens e domésticos. No presente estudo, o molusco Lymnaea columella foi coletado de plantações urbanas de agrião e a morfologia das cercárias liberadas por eles foi analisada por microscopia eletrônica de varredura leve e de varredura. As larvas foram identificadas como xifidiocercárias, pertencentes ao grupo das Cercariae Ornatae, Ordem Plagiorchiiformes. Análises histológicas da glândula digestiva dos moluscos infectados evidenciaram esporocistos, com formação de granuloma e metaplasia do tecido epitelial.

Morphological Characteristics and Phylogenetic Trends of Trematode Cercariae in Freshwater Snails from Nakhon Nayok Province, Thailand

The prevalence of cercarial infection in freshwater snails and their evolutionary trends were studied in Nakhon Nayok province, Thailand. A total of 2,869 individual snails were examined for parasitic infections. The results showed that 12 snail species were found to host larval stages of trematodes with an overall prevalence of 4.7%. The infected specimens included 7 types at the cercarial stage; cercariae, megalurous cercariae, echinostome cercariae, furcocercous cercariae, parapleurolophocercous cercariae, virgulate cercariae, and xiphidiocercariae. Regarding molecular identification, ITS2 sequence data of each larval trematode were analyzed, and a dendrogram was constructed using the neighbor-joining method with 10,000 replicates. The dendrogram was separated into 6 clades (order/family), including Echinostomatida/Echinostomatidae, Echinostomatida/Philophthalmidae, Opisthorchiida/Heterophyidae, Plagiorchiida/Prosthogonimidae, Plagiorchiida/Lecithodendriidae, and Strigeatida/Cyathocotylidae. These findings were used to confirm morphological characteristics and evolutionary trends of each type of cercariae discovered in Nakhon Nayok province. Furthermore, this investigation confirmed that the ITS2 data of cercariae could be used to study on phylogenetic relationships or to determine classification of this species at order and/or family level when possible.

Freshwater gastropods of the Baixada Maranhense Microregion, an endemic area for schistosomiasis in the State of Maranhao, Brazil: I - qualitative study

Introduction: The Baixada Maranhense Microregion currently has the highest prevalence of schistosomiasis in the State of Maranhão, likely because this parasitosis is characterized as an occupational disease, and increased contact with water increases the risk of infection by Schistosoma mansoni. This paper reports the results of the first comprehensive freshwater malacological survey performed in the Baixada Maranhense Microregion. Methods: Freshwater mollusks were collected from the twenty-one municipalities of the Baixada Maranhense Microregion and from Bacurituba and Cajapió and were evaluated for infection by trematodes. Results: A total of 9,129 mollusks were collected (sixteen species), which included the first records of six species in the State of Maranhão: Gundlachia radiata, G. ticaga, Hebetancylus moricandi, Plesiophysa guadeloupensis, Pomacea bridgesii diffusa and Omalonyx sp. Biomphalaria glabrata was found in five municipalities, whereas B. straminea was found in nine. Biomphalaria glabrata and B. straminea were observed in syntopy in Pinheiro and São Bento. Of the 990 specimens of B. glabrata and the 2,109 specimens of B. straminea that were exposed to and/or analyzed for the presence of larval trematodes, only a single specimen of B. glabrata (0.1%) from São Bento shed S. mansoni. Other larval trematodes were first observed in mollusks from the State of Maranhão. Conclusions: These results indicate that the study area is epidemiologically important due to the presence of two natural vectors of schistosomiasis and the active transmission of schistosomiasis, which was confirmed in the infected specimen that was collected in this study. .

Seasonal variation in toxicity of citral against Fasciola larva

Objective:To test whether the larvicidal activity of citral against Fasciola varies by season. Methods:Mortality of Fasciola larva in different month of year (2011-2012) in in vitro and in vivo condition were observed at 2 h, 4 h, 6 h and 8 h exposure of citral. Results:In vitro toxicity of citral against redia was highest in between the June to August (8 h LC50: 2.58-2.62 mg/L), whereas against cercaria 8 h LC50 was in between 3.44-2.62 mg/L. Highest in vivo toxicity against redia was noted in between June to August (8h LC50: 4.20-5.09 mg/L). The lowest toxicity was observed from November to April. The highest temperature, free carbon dioxide, and lowest pH, dissolved oxygen were observed from June to August. Conclusions:The present study conclusively shows that varying a biotic factor can significantly alter the in vitro and in vivo toxicity of citral against sporocyst redia and cercaria larva.

Jatropha seed oils extracted by different methods and their effect on killing cercaria of Schistosoma japonicum / 中国血吸虫病防治杂志

Objective To evaluate the effect of Jatropha see soma japonicum so as to screen the optimum process and formulations. Methods The cercaria directly contacting tests with Jatro-pha seed oils extracted by 6 different extraction processes were carried out,and the mouse immediate contacting cercaria infection trials with different formulations of Jatropha seed oil and various additives were performed. Results With 95%ethanol,the ratio of material to liquid being 1∶8,and 2 h extraction,the oil extraction rate was 30.7%. The cercaria directly contacting tests showed that 6 kinds of Jatropha seed oil killed all cercaria within 30 min. In the mouse immediate contacting cercaria infection trials,the worm declined rate of Jatropha seed oil liquid was 70.97%,and the worm declined rate of the sample added with benzyl benzoate was 58.87%,and the worm declined rate of the sample added with laurocapram was 77.42%. The worm declined rate of the sam-ples added with benzyl benzoate,dibutyl phthalate and laurocapram was 100%. Conclusion The process with 95%ethanol,the ratio of material to liquid being 1∶8,and 2 h extraction is the optimum,and the Jatropha seed oil has a good killing schistosome cercaria effect.

Surveillance and forecast system of schistosomiasis in Jiangsu Province ⅥDetection technology of water infectivity based on enrichment of Schistosoma japonicum cercariae on water surface / 中国血吸虫病防治杂志

Objective To explore the enrichment technique of Schistosoma japonicum cercariae on the water surface,so as to establish a new method combined with the existing technology to detect the cercarial infested water body quickly and sensitive-ly. Methods Soybean oil,gasoline,kerosene and isophorone were screened as expanding agents. The cercariae were enriched by the thrust of the expanding agents when diffusing on the water surface,and PE adsorption film and C-6 film were applied to seize them so as to determine the infectivity of the water quickly. The relationship between the dose of expanding agents and dif-fusion radius were explored. Results Gasoline,kerosene and isophorone were suitable expanding agents,and the diffusion ef-fect of isophorone was the best. After the enrichment by the expanding agents,the detection rate of cercariae of the method seiz-ing cercariae with the film significantly improved in the water. Conclusion This new method could effectively improve the de-tection rate of the cercarial infested water and is suitable for the low-degree infested water.

Mechanism on symbiosis of Oncomelania hupensis and Schistosoma j aponicum / 中国人兽共患病学报

ABSTRACT:As the only intermediate host of Schistosoma j aponicum ,Oncomelania hupensis is an important link of schis‐tosomiasis .It plays an important role in the transmission of schistosomiasis .This article mainly demonstrates the following as‐pects :the invasion of schistosome miracidium into O .hupensis ,the growth of sporocyst ,and the mature and escape of cercari‐ae ,which would provide laboratory data from literatures for revealing the symbiotic relationship between O .hupensis and S . japonicum .However ,the symbiotic relationship between O .hupensis and S .japonicum is too complex to description com‐pletely .Therefore ,the symbiotic relationship will be the focus of future research .

Discovery and biology of Schistosoma haematobium / 中国血吸虫病防治杂志

Schistosomiasis is a neglected tropical disease that severely threatens human health and affects the socioeconomic development. The causative agent that parasitizes in humans mainly involves Schistosoma japonicum,S. mansoni,S. haematobi-um,S. intercalatum and S. mekongi. As the firstly identified schistosome,S. haematobium infection is found to strongly correlate with bladder cancer. This paper mainly reviews the discovery,morphology and life cycle of S. haematobium.

Fasciolosis Control: Phytotherapy of Host Snail Lymnaea acuminata by Allicin to Kill Fasciola gigantica Larvae.

Aims: Fasciolosis is a widely distributed disease affecting the lives of herbivorous animals and human. The causative agents are Fasciola hepatica and F. gigantica. Snail Lymnaea acuminata is the intermediate host of Fasciola species. Sporocyst, redia and cercaria are the larval stages found in the snail body. Methodology: The destruction of these larvae in intermediate host is one of the important methods to abolish the incidences of fasciolosis without, killing the snail. Mortality of larvae in in vitro and in vivo condition was observed at 2h, 4h, 6h and 8h, exposure of allicin an active component of Allium sativum. Results: Abiotic factors alter the toxicity of allicin against F. gigantica larvae in different months of year 2011-2012. Highest in vitro toxicity of allicin against redia larva was noted in July (8h LC50 0.001 mg/ml), where as in case of cercaria larva it was in month of June (8h LC50 0.005 mg/ml). Highest toxicity in in vivo treatments against redia and cercaria larvae was observed in February (8h LC50 0.013mg/L and 0.010 mg/L, respectively). The highest temperature, free carbon dioxide, lowest pH and dissolved oxygen were noted in the months of June to August. Conclusion: In vitro and in vivo treatment of allicin against Fasciola larvae is one of the new approaches to control the fasciolosis, without killing the host snail.

In vitro PHYTOTHERAPY OF VECTOR SNAILS BY BINARY COMBINATIONS OF LARVICIDAL ACTIVE COMPONENTS IN EFFECTIVE CONTROL OF FASCIOLIASIS / Fitoterapia in vitro de caramujos vetores por combinações binárias de componentes ativos larvicidas como controle efetivo de fasciolíase

SUMMARY A food-borne trematode infection fascioliasis is one among common public health problems worldwide. It caused a great economic loss for the human race. Control of snail population below a certain threshold level is one of the important methods in the campaign to reduce the incidence of fascioliasis. The life cycle of the parasite can be interrupted by killing the snail or Fasciola larva redia and cercaria inside of the snail Lymnaea acuminata. In vitro toxicity of different binary combinations (1:1 ratio) of plant-derived larvicidal active components such as citral, ferulic acid, umbelliferone, azadirachtin and allicin against Fasciola redia and cercaria were tested. The mortality of larvae was observed at 2h, 4h, 6h and 8h of treatment. In in vitro condition azadirachtin + allicin (1:1 ratio) was highly toxic against redia and cercaria (8h LC50 0.006 and 0.005 mg/L). Toxicity of citral + ferulic acid was lowest against redia and cercaria larvae. .

RESUMO A infecção alimentar pelo trematóide da fasciolíase é uma dentre os mais comuns problemas de saúde pública mundiais, causando grande prejuízo econômico para a humanidade. Controle da população de caramujos abaixo de determinado nível é um dos métodos no campo mais importantes para a redução da incidência da fasciolíase. O ciclo de vida do parasita pode ser interrompido pela morte do caramujo ou da larva redia e cercária da Fasciola dentro da Lymnaea acuminata. Foi testada a toxicidade in vitro das diferentes combinações binárias (relação 1:1) entre os vários componentes larvicidas ativos da planta tais como citral, ácido ferúlico, umbeliferone, azadiractina, e alicina contra a Fasciola redia e a cercária. A mortalidade das larvas foi observada após duas, quatro, seis e oito horas de tratamento. A condição in vitro azadiractina + alicina (relação 1:1) foi altamente tóxica contra redia e cercária (8h LC50 0,006 e 0,005 mg/L). Toxicidade do citral + ácido ferúlico foi a mais baixa contra redia e larvas de cercária. .

The Pampulha reservoir remains a potential urban focus of schistosomiasis mansoni in Brazil: changes in the occurrence patterns of Biomphalaria species and a new record of the parasite

Introduction The Pampulha reservoir has long been a focus of schistosomiasis transmission in Belo Horizonte, State of Minas Gerais, Brazil. The last malacological study conducted in this urban reservoir was more than two decades ago, and thus, an update on the distribution of the species of Biomphalaria as well as new data on the presence of Schistosoma mansoni in this water body are required. Methods The current distribution of Biomphalaria spp. in the Pampulha reservoir and their infection with S. mansoni was evaluated during 55 malacological surveys conducted between 2009 and 2012. Results Biomphalaria straminea displayed a high population density and distribution, and 13.7% (2,233/16,235) of the specimens collected were infected with larval trematodes other than Schistosoma mansoni. Biomphalaria tenagophila and Biomphalaria glabrata, species currently presenting a restricted distribution and small populations, displayed trematode infection rates of 15.2% (98/644) and 13% (83/640), respectively. Thirteen (2%) specimens of B. glabrata were found to be infected with S. mansoni. In addition, a historical review based on previous and new data on the occurrence patterns of Biomphalaria species in this reservoir is presented. Conclusions The results indicate that the Pampulha reservoir remains a potential focus of urban schistosomiasis in Brazil, and significant changes in the occurrence patterns of Biomphalaria species were verified. .

Three new species of cercariae from Melanopsis praemorsa (L. 1758, Buccinum) snails in Al-Bathan fresh water body, Palestine

Objective: To investigate other new species of cercariae encountered in Melanopsis praemorsa (M. praemorsa) snails collected from Palestine. Methods: A total of 1 100 M. praemorsa were collected from Al-Bathan water body, Palestine, from November, 2010 to November, 2011. Cercariae in M. praemorsa were obtained by emerging and crushing methods. Results: Other three new different species of cercariae have been identified from this snail. These species were Xiphidiocercaria (Cercaria melanopsi palestinia IV), Microcercous (Cercaria melanopsi palestinia V) and Longifurcate cercaria (Cercaria melanopsi palestinia VI). The infection rate ofM. praemorsa with these three different cercariae was (42.2%). Coinfection with Xiphidiocercariae and Longifurcate cercariae or Xiphidiocercariae and Microcercous cercariae has been noted and coinfection rate was 1.23% among the infected snails. The highest cercarial infection rate was in June (64.3%). No infected snails were found in September. It was also noted that infected snails attained a larger size than uninfected ones and all infected snails had a size between 17-22 mm (average 20 mm). Conclusions: Our studies imply that there are potentially more new species of trematodes in this area than were found until now. Due to the presence of infected M. praemorsa and may be species of other snails, water resources could be contaminated by the emerging new cercariae, consequently attack the local people directly via the skin or are transferred to them by metacercariae ingestion. More surveys are needed to identify the real prevalence of the trematodes both in human and animal hosts, and also to determine the range of snail hosts of the parasite in enzootic areas of the disease, as well as the life cycle and biology of trematodes and its effects on man should be elucidated.

Cercaria caribbea LVIII Cable, 1963 (Digenea: Cyathocotylidae) in the Republic of Korea and Its Surface Ultrastructure

Cercaria caribbea LVIII Cable, 1963 (Digenea: Cyathocotylidae) was detected from a brackish water gastropod species (Cerithideopsilla cingulata) in a coatal area of Shinan-gun, Jeollanam-do (Province), the Republic of Korea, and its surface ultrastructure was studied using a scanning electron microscope. The cercariae were found freely swimming or enveloped within daughter sporocysts when the snail host was mechanically broken. They were morphologically characterized by a linguiform and ventrally concave body, a long and bifurcated tail, and the presence of a holdfast (=tribocytic) organ posterior to the ventral sucker. On the whole ventral and dorsal surfaces, peg-like tegumental spines were densely distributed. Around the oral sucker, several sensory papillae, each with a short cilium, were distributed, and on the tail, sensory papillae, each with an extensively long cilium, were observed. This is the first record describing a cyathocotylid cercaria from a brackish water gastropod in the Republic of Korea.

Using modified crushing-cercariae escaping method to detect infected snails / 中国血吸虫病防治杂志

Objective To evaluate the detection rate and the efficiency of the modified crushing-cercariae escaping method.Methods The detection rates of the modified crushing-cercariae escaping method and the crushing methods were compared by using a double-blind control experiment with the latter as a gold standard.meanwhile the number of the cercariae was quantified.The efficiency of the two methods aforementioned and the cereariae escaping method were compared in field.Results The detection rate of the modified crushing-cercariae escaping method was 100%.the average number of cercariae in each infected snail was (4 778±1 157);and the number in certain volume of water sample was positively correlated with the number of infected snails.The efficiency of the modified menthed Was 18.2 times and 17.3 times as high as those of the crushing method and cereariae escaping method,respectively.Conclusions The modified crushing-cercariae escaping method Can detect the infected snails quicky and Can quantify the number of infected snails and cercariae,and is suitable for the detection of infected snails in large number.