Epidemiology of cercarial stage of trematodes in freshwater snails from Chiang Mai province,Thailand

Objective:To investigate the epidemiological situation of cercarial trematodes infection in freshwater snails from different water resources in Chiang Mai province,Thailand.Methods:The snail specimens were collected from 13 districts of Chiang Mai province during April 2008 to February 2012.The prevalence of cercarial infection in snails was investigated using the crushing method.The drawing was done with the help of a camera lucida for the morphological study.Results:A total of 2479 snail individuals were collected and classified into 7 families,11 genera,and 14 species,Among them,8 snails species were found to be infected with an overall prevalence of 17.27%(428/2479),which infected with nine groups of cercariae;gymnocephalous cercaria,strigea cercaria,megalurous cercaria,monostome cercaria,parapleurolophocercous cercaria(Haplorchis cercaria),pleurolophocercous cercaria,furcocercous cercaria(Transversotrema cercaria),xiphidiocercaria,and virgulate cercaria.The parapleurolophocercous cercaria was found to be the dominant type among the cercarial infection in the snails(64.25%).Conclusions:The various species of snails found in the research location act as the intermediate hosts for the high prevalence of parasitic infection of many species of mammals.This work will provide new information on both the distribution and first intermediate host of trematodes.

Chromosome-level genome assembly of the freshwater snail Bellamya purificata(Caenogastropoda)

DEAR EDITOR,Bellamya purificata(Gastropoda:Caenogastropoda;Architaenioglossa;Viviparidae:Bellamyinae;Sinotaia),a homotypic synonym of S.purificata,is widely distributed in freshwater habitats in Asia.It is an economically important edible snail and plays a vital function in freshwater wetland ecology.However,genomic resources for this snail are lacking and no reference genome has been released.In this study,we constructed the first chromosome-level genome of B.purificata using PacBio long-read sequencing and high-throughput chromosome conformation capture(Hi-C)technology.

Epidemiological situation and molecular identification of cercarial stage in freshwater snails in Chao-Phraya Basin, Central Thailand

Objective: To investigate the prevalence of cercarial trematode infection in snails and to examine the reconstruction of the phylogenetic relationship to explain the molecular system of cercarial stage trematodes to estimate the infection rate of in the definite host from the Chao-Phraya Basin.Methods: The snails were collected from 10 provinces of the Chao-Phraya Basin,Thailand by stratified sampling method. The snails were examined for cercarial infection by the crushing method. All DNA specimens were amplified with internal transcribed spacer 3(ITS3) and ITS4 primer based on PCR technique. The sequence data were aligned and used to reconstruct the phylogenetic tree by unweighted pair-group method with arithmetic means with 10 000 bootstraps.Results: The overall rate of cercarial infection was found to be 5.90%(122/2 067). Snails in the family Thiaridae were found to be in the highest prevalence followed by Lymnaeidae, Bithyniidae, Planorbidae, Viviparidae, and Ampullariidae, respectively, while the Buccinidae family(Clea helena) did not reveal any infections. The frequently found species of cercariae were parapleurolophocercous cercariae, cercariae and megarulous cercariae. The monophyletic tree separated the snails into five groups comprised of Heterophyidae, Strigeidae, Lecithodendriidae, Philophthalmidae and Echinostomatidae using the sequence of Angiostrongylus cantonensis as an out-group.Conclusions: This study was the first to report on cercarial infection in the Chao-Phraya Basin, Thailand. This revealed that a high variety of freshwater snails were infected by cercariae stage trematodes with a high prevalence. The sequence data of ITS2 can be used to investigate the phylogenetic relationships of trematodes at the family level and in each clade of different families separated by the definitive hosts.

Prevalence of cercarial infections in freshwater snails and morphological and molecular identification and phylogenetic trends of trematodes

Objective:To investigate the prevalence of cercarial infections in freshwater snails from several water sources in Nakhon Nayok,Nonthaburi,and Pathum Thani provinces of Central Thailand,and to reconstruct a phylogenetic tree for improved understanding of the relationships in the cercarial stage.Methods:The snail specimens were collected from 34 total sampling sites and investigated for cercarial infections using the crushing method.The cercarial specimens were classified and used for the phylogenetic tree analysis using the Internal Transcribed Spacer 2(ITS2).Results:A total of 1921 snail specimens were classified into five families and seven species.The results showed that four snail species were identified as intermediate hosts of the larval stages of trematodes,with an overall prevalence of infection of 2.45%(47/1921).The infected snail specimens included five groups of the cercarial type:cercariaeum cercariae,echinostome cercaria,megalurous cercaria,parapleurolophocercous cercaria,and xiphidiocercariae.This is particularly true of xiphidiocercariae,which was found to be the dominant type among cercarial infections in bithyniid snails by approximately 38.00%.With regard to molecular identification,the phylogenetic tree was reconstructed using the neighbor-joining method with 10000 bootstraps and separated the trematodes into three clades:Echinostomatoidea,Microphalloidea and Opisthorchioidea.Conclusions:The study reveals a high prevalence of cercarial infection for each cercarial type and maturation into a definite trematode genus and delineates morphological characteristics and evolutionary trends among each larval trematode in Nakhon Nayok,Nonthaburi and Pathum Thani provinces.In addition,the ITS2 sequence data of cercariae could be used to examine classification of these species at the family level.

齐齐哈尔市域淡水螺盾盘吸虫感染情况调查

目的了解齐齐哈尔市淡水螺体内盾盘吸虫的种类及其感染情况。方法于2022年9—12月在齐齐哈尔市内随机购买淡水螺数次,根据淡水螺形态鉴定螺的种类,并在解剖显微镜下解剖淡水螺,分离淡水螺内的吸虫,采用醋酸洋红进行染色、制片后进行虫种鉴定、统计不同种类淡水螺体内吸虫的感染情况。结果根据形态学特征鉴定所获本市淡水螺为中华圆田螺和东北田螺两种;共解剖淡水螺2603只,其中中华圆田螺2131只,东北田螺472只;发现本市淡水螺体内有盾盘吸虫寄生,且经鉴定为贝居盾盘吸虫;中华圆田螺体内发现盾盘吸虫202只,东北田螺体内发现盾盘吸虫0只。中华圆田螺感染率为8.81%,东北田螺感染率为0,中华圆田螺平均感染度为1.46。结论首次在嫩江水域中华圆田螺体内发现贝居盾盘吸虫,而东北田螺体内无寄生。

Types of trematodes infecting freshwater snails found in irrigation canals in the East Nile locality,Khartoum,Sudan

Background:The planorbid freshwater snails of the two genera,Biomphalaria and Bulinus-have been vigorously studied due to the role they play as intermediate hosts of schistosomiasis.In Sudan specifically,most studies have focused on the chemical and ecological control of the two genera,but few studies have looked at their biological control.This study explored the coexistence of other species of freshwater snails and the two genera along with their trematode infections in relation to a number of environmental factors in the East Nile locality,Khartoum state,Sudan.Methods:Freshwater snails from irrigation canals(abueshreens)were sampled monthly from January 2004 to December 2005.The snails were examined for trematode infections by cercarial emergence immediately after collection and then weekly for an additional four weeks to allow for the maturation of prepatent infections.Vegetation cover in the study sites as well as the physicochemical characteristics of the water,including temperature,were also recorded.Results:A total of 10,493 snails,representing seven species,were collected.The most abundant species was Biomphalaria pfeifferi,representing 48.6%of the sample.Overall,14.1%of the snails were found to be shedding some type of cercariae.Five species were found to have infections;among these the Bulinus truncatus species was found to be the most heavily infected,with an overall prevalence of 46.2%.Double infections were recorded in only two B.truncatus snails and one Cleopatra bulimoides snail.Twenty different morphotypes of cercariae were recorded,seven of which appeared not to conform to previously described cercariae from Africa.Xiphidiocercariae type 1 was the most common type of cercariae recovered,accounting for 44.3% of all infections.The density of snails tended to be lower during the summer months than the winter months,except for M.tuberculata snails,which were not affected by seasonal changes.Conclusion:The findings of this study indicate that besides schistosomes,other larval trematodes are found,and some use the same intermediate hosts as the schistosomes.Further studies should be conducted to determine whether some of these trematodes could be manipulated for the biological control of schistosomiasis.

Environmental determinants of distribution of freshwater snails and trematode infection in the Omo Gibe River Basin,southwest Ethiopia

Background:Determination of infection rates of snail populations is one of the basic tools for epidemiological studies of snail borne diseases.In this study,we opted to determine the trematode infection of freshwater snails in the Omo-Gibe River Basin,southwest Ethiopia.Methods:We collected snail samples from 130 observation sites in lakes,wetlands,rivers,reservoirs and irrigation canals surveyed during the dry season(March to May)in 2016.The snail samples were examined for trematode infections by cercarial shedding immediately after collection.Habitat conditions,water quality,human water contact practices and other human activities were assessed at each survey site.A redundancy analysis(RDA)was used to examine the relationship between cercarial infection and environmental variables.The statistical significance of eigenvalues and cercariae-environment correlations generated by the RDA were tested using Monte Carlo permutations at 499 permutations.Results:A total of 3107 snails belonging to five species were collected.The most abundant species was Biomphalario pfeifferi,representing 66%of the total collection.Overall,109(3.6%)of the snails were found infected with trematodes(cercariae).Biompholario pfeifferi was found to be the most highly infected,accounting 85%of all infected snails.A total of eight morphologically different types of cercariae were recorded,which included:Echinostoma cercariae,brevifurcate apharyngeate distome cercariae,amphistome cercariae,brevifurcate apharyngeate monostome cercariae,xiphidiocercariae,longifurcate pharyngeate distome cercariae,strigea cercariae and unidentified cercariae.Brevifurcate apharyngeate distome cercariae,and Echinostoma cercariae were the most abundant cercariae,accounting for 36 and 34%of all infection,respectively.The mean concentration of water conductivity and 5 days biological oxygen demand were higher in irrigation canals and lake sampling points.Human activities such as open field defecation,urination,livestock grazing,farming,and swimming were highly correlated with trematode infection.Conclusions:The abundance,occurrence and infection rates of snail species were largely influenced by water physicochemical quality,sanitation and water contact behaviour of the inhabitants.Human activities,such as open field defecation and urination,livestock grazing,farming,and swimming were important predictors of the abundance of cercariae.Therefore,awareness creation should be implemented for proper containment of excreta(urine and faeces)and reducing human and animal contacts with surface waters to reduce snail-borne disease transmission.

Hidden diversity revealed in the freshwater snails,Bythinella and Pseudamnicola,in the Island of Crete

Crete with its complex geomorphological history is the island with the highest number of endemism observed in animal and plant taxa throughout the Aegean archipelago.While other groups of organisms within Crete are well-studied,the freshwater gastropod fauna still remains poorly investigated.Bythinella and Pseudamnicola,are 2 genera of freshwater springsnails,both present on the island,inhabiting springs and other freshwater habitats.Here,we conduct a comprehensive study on the distribution of the different genetic lineages of the 2 gastropod genera in order to assess the mode of their differentiation on the island and infer the actual number of species present in the island.Towards these aims,sequence data from the mitochondrial gene were used and analyzed within a phylogenetic framework.For Bythinella,our results strongly support at least 5 delineated Bythinella spp.inhabiting Crete,which correspond to the already described species from previous studies with the addition of a new one.Bythinella analyses reveal an old time-frame of differentiation with vicariant phenomena being more likely the main drivers shaping the present-day distribution of the genus’genetic lineages.For Pseudamnicola,our data indicate the presence of at least 2 delineated Pseudamnicola spp.with a differentiation more consistent to an isolation-by-distance pattern of a relatively recent origin.Dispersion processes followed by isolation of the populations and/or recent speciation,seem to be the underlying process for the current distribution of Pseudamnicola lineages.

湘江中游江段螺类的种类组成及区系分析

报道了湘江中游江段螺类的调查结果,计有螺类31种(其中5种为湖南省新记录),分别隶属于腹足纲6科11属,其中主要是田螺科的种类.对它们的种类组成、区系、种群大小、分布与栖息环境的关系进行了分析,并讨论了城镇污水未经处理直接排放及修河拦坝对螺类生存环境的影响.

洞庭湖及其周围主要水域的螺类

1989～1992年作者对洞庭湖及其周围主要水域的螺类进行了初步调查,计有螺类27种(其中2种为湖南省新纪录),分别隶属于腹足纲的5科12属、本文叙述了该地区螺类种的纪要,对它们的种群大小、分布概况、优势种和区系特点进行了分析.

阿达滩盆地古近纪淡水腹足类化石的发现及其地质意义

东昆仑西段阿达滩盆地早新生代陆相碎屑岩沉积建造,原先被笼统认为属"下第三系"。1∶25万库郎米其提幅区调中,在该碎屑岩建造中首次发现淡水腹足类化石:假菊石型南方圆螺黄河亚种AustralorbispseudoammoniushuanghoensisYu,实椎螺(未定种)Lymneasp.根据含化石地层的岩相特征及腹足类化石生存时代,阿达滩盆地的下第三纪应属古近纪渐新世的干柴沟组下部,据该套地层的存在及不整合覆盖于其上的早更新世七个泉组分析,推断阿达滩盆地在渐新世末存在一次较强规模的隆起。

不同初始螺类密度对沉水植物刺苦草Vallisneria spinulosa Yan及其附着藻类的影响

大型水生植物及其附着藻类是浅水湖泊中的重要初级生产者。淡水螺类作为重要的初级消费者,其密度对沉水植物及其附着藻类的影响存在争议。本研究设置4种初始螺类密度(0、40、80、240 ind·m-2),研究淡水螺类(椭圆萝卜螺Radix swinhoei H.Adams)对刺苦草(Vallisneria spinulosa Yan)及其附着藻类的直接牧食作用和螺类种群的变化。结果显示,在添加螺处理中,刺苦草和人工基质表面附着藻类的生物量显著降低,同时沉水植物的生长显著增加,在较高初始密度螺类处理中刺苦草产生更多的分株。到实验结束时,螺类的死亡率较高,但3个有螺处理间螺类鲜重无显著差异,而高初始密度螺类条件下的最终密度仍较高,同时个体重量(均重)也较小。在中富营养条件下淡水螺类可以直接牧食沉水植物叶片,但对植物生长的抑制作用不显著,有可能是因为沉水植物并不能作为唯一的食物来源维持螺类种群,同时螺类的种群结构受到水体营养水平等因素的制约。

塔里木河上游水域淡水螺种类调查

记述了2008年4～10月在塔里木河上游水域采集到的淡水螺17种，并对各个采集地区的环境条件进行了简略的描述．通过查找资料记录各种螺作为中间宿主可能导致的寄生虫病，其中有些寄生虫严重影响了塔里木河流域畜牧业的发展。对塔里木河上游存在的淡水螺做的种类调查，经鉴定共有8个属14个种，其中有经济价值的3种，能作为寄生虫中间宿主的有10种，同时对采集到的螺的生活条件做了记录。

麻疯树素对钉螺及淡水鱼的生物毒性研究

将麻疯树素配成不同浓度,观察不同时间钉螺及淡水鱼的死亡率。试验设萃取剂和清水对照。结果麻疯树素浓度为0.75 mg/L 24 h钉螺开始死亡,6.00 mg/L 48 h钉螺死亡率100%,室内浸杀钉螺24 h的LC50为3.40 mg/L;该药对淡水鱼苗有中度毒性,浸杀鲫鱼苗96 h的LC50为1.05 mg/L,浸杀草鱼苗96 h的LC50为2.78 mg/L。麻疯树素是一种有应用潜力的植物杀螺剂。

长沙地区的淡水螺类

本文报道了湖南长沙地区淡水螺类的调查结果,计有淡水螺类25种,分别隶属于腹足纲的5科、10属,其中3种为湖南省首次记录,并阐述了它们的生态和地理分布、优势种等情况。同时结合长沙地区的特点,叙述了它们的经济意义。

酸性水对淡水螺类存活、生长与繁殖的影响

研究了酸性水对椭圆萝卜螺和铜锈环棱螺等淡水螺类存活、生长及繁殖的影响。结果表明,椭圆萝卜螺对低pH值的耐受能力,96小时LC_(50)值为pH3.96。pH值低于5.0时,淡水肺螺类产的卵袋数量较少,卵孵化时间较长,幼螺生长较缓慢。铜锈环棱螺仔螺在低pH(对照组)下生长到第35和45天时,其体长生长率分别为1.21和1.07％,而pH5.0组则仅有0.18和0.29％。pH5.5对淡水肺螺类无明显影响,pH3.0则不能生存。

螺肉盐溶蛋白提取工艺优化及其加工特性

以新鲜螺肉为原料,对其盐溶蛋白提取工艺参数进行优化,并测定其乳化性、起泡性和保水性等主要加工性质。结果表明:螺肉中盐溶性蛋白的最佳提取条件为盐浓度0.7mol/L、pH值8.0、固液比1:6(g/mL)、浸取时间24h,该条件下盐溶性蛋白质提取率为13.6%。其最佳乳化活性为27.67m^2/g,ESI指数最大值为0.62,略低于大豆分离蛋白,在碱性条件下其起泡能力和泡沫稳定性较好,分别可达到68%和42%,优于大豆分离蛋白,保水性最大为78.25%。螺肉盐溶蛋白具备制成肉糜制品品质改良剂的性能,是一种较好的功能性蛋白质资源。

贵州部分地区陆生贝类调查研究(腹足纲:前鳃亚纲 ,肺螺亚纲)

首次系统报道贵州省陆生贝类名录共118种(其中含待定种13个),分隶于18科48属,其中有8新种(有6新种已另文报道),即贵阳弯螺SinoeeneaguiyangensisLuoetChen,1998,水田坝贝喇叭螺Boysidia(Bensonella)shuitianbaensisLuoetChen,1998,贵阳喇叭螺Boysidia(Boysidia)guiyangensisLuoetChen,1998,黄果树喇叭螺Boysidia(Boysidia)huangguoshuensisLuoetChen,2000,天星桥喇叭螺Boysidia(Ban sonella)tianxingqiaoensisLuoetChen,2000,茂兰腹皱螺GastroptychiamaolanensisLuoetChen,2002,茂兰沟螺Dioryxmaolanensissp.nov.(另文报道),茂兰果瓣螺Carychiummaolanensissp.nov.(另文报道)。对其种类组成和分布进行了讨论。

鄱阳湖夏季淡水螺类群落结构

2007年4月-2007年7月对鄱阳湖的淡水螺类进行了较为广泛的定性定量采集。标本经整理，计有螺类26种，隶属7科15属。优势种为铜锈环棱螺（Bellamya aentginosa）、纹沼螺（Parafossarulus striatulus）和方格短沟蜷（Semislcospira cancellata）。平均生物量和密度分别为69．60g／m^2和110，27ind．／m^2。不同断面的Shannon—Wiener多样性指数H＇的范围在1，11—2．11；均匀度指数Jsww的范围为0，76—0．99。

不同密度铜锈环棱螺对沉水植物生长和水质的影响

通过试验研究不同密度铜锈环棱螺(Bellamya aeruginosa)对苦草(Vallisneria natans)和金鱼藻(Ceratophyllum demersum)生长及水质的影响。试验结果表明:铜锈环棱螺的存在显著促进了沉水植物的生长,高密度组苦草和金鱼藻的相对生长率分别是对照组的2.16和1.66倍,高密度组苦草和金鱼藻的相对伸长率分别是对照组的1.18和1.25倍;铜锈环棱螺的存在对水质有一定负面影响,水体电导率随着螺密度的增加而升高,溶解氧浓度随着螺密度的增加而降低,pH值、氧化还原电位和叶绿素浓度随着螺密度的增加没有一致的规律;水体氮的去除率随螺密度的增加呈下降趋势,高密度组苦草和金鱼藻对氮的去除率相对于对照组分别下降了70.0%和64.5%,磷的去除率组间没有显著差异;铜锈环棱螺密度对水体氮浓度变化起主要作用,方差占比为64%,沉水植物不同物种对水体磷浓度变化起主要作用,方差占比为72.54%。