The prolonged use of niclosamide as a molluscicide for the control of Schistosoma mansoni.

Applications of niclosamide at three-monthly intervals were undertaken for 14 years in foci of Biomphalaria glabrata in the water sources of Peri-Peri (Capim Branco, MG). All the residents of the area were submitted to an annual fecal examination (Kato/Katz) and those individuals eliminating Schistosoma mansoni eggs were treated with oxamniquine. A malacological survey was undertaken at three-monthly intervals by means of ten scoops with a perforated ladle each ten metres along the two banks of the ditches and streams of the region. Where snails were found, molluscicide was applied by means of dripping or aspersion using a 3 ppm aqueous suspension of niclosamide. Initially, a mean of 14.3% of snails in the region were found to be eliminating cercariae. Following the first four applications of molluscicide, this was reduced to 0.0% and maintained at about 1.5% throughout the program. Thus, there was a continued possibility of schistosomiasis transmission in the area and it was observed that the population of snails reestablished itself within three months of molluscicide application. The results obtained in this study do not encourage the continual use of niclosamide as the only method of control of schistosomiasis.     

两种塑料地膜在云南省有螺排灌沟的短期灭螺效果比较

目的观察并比较无色和黑色塑料地膜覆盖法在云南省有螺排灌沟的短期灭螺效果。方法选择钉螺密度较高的排灌沟,设单纯无色地膜覆盖组、单纯黑色地膜覆盖组、无色地膜覆盖施药组和黑色地膜覆盖施药组4个组。在实验前以及覆盖地膜后7、14、21、30 d对各组进行螺情调查,观察钉螺死亡率,并定时记录土表温度、膜内土表及土下5、15cm处温度及每日天气情况。结果单纯无色地膜覆盖组钉螺平均死亡率(15.29%)略高于单纯黑色地膜覆盖组(6.56%)(P0.01),两组灭螺效果均不理想。两种地膜覆盖并辅以灭螺药,均能增加钉螺死亡率;无色、黑色地膜施药覆盖组钉螺平均死亡率分别为40.80%、50.15%,差异无统计学意义(P0.05)。两种塑料地膜均能提高膜内土表及土内温度,并且随着覆盖时间的延长膜内土壤温度均呈升高趋势,黑色地膜覆盖后30 d平均膜内土表温度高于无色地膜。结论云南省有螺排灌沟不宜大范围使用地膜覆盖法灭螺,如必须使用地膜,需辅以灭螺药物。     

杀虫丁与氯硝柳胺现场灭螺效果的对比实验观察

目的比较杀虫丁和氯硝柳胺现场杀螺效果,探索有效灭螺剂量及影响灭螺效果的有关因素。方法以杀虫丁为实验组、氯硝柳胺为实验对照组、清水为空白对照组,在不同类型的有螺地区进行现场浸杀和喷洒灭螺实验,观察比较不同浓度、作用时间和温度下钉螺校正死亡率。结果现场浸杀,杀虫丁1.0mg/L浓度组浸杀48h后肋壳钉螺校正死亡率为82.8%,光钉螺校正死亡率为34.3%,显著低于同浓度的氯硝柳胺组(P<0.01)。现场喷洒,杀虫丁1.0g/m2、1.5g/m2、2.0g/m23个浓度组喷洒灭螺后7-30d,洲滩和河滩肋壳钉螺校正死亡率均<50.0%,杀螺效果显著低于同浓度的氯硝柳胺组(P<0.01)。结论在本次实验条件下,氯硝柳胺现场浸杀和喷洒灭螺效果均明显优于杀虫丁。     

山丘地区“农达”除草后药物灭螺效果的观察

目的探索在山丘地区用除草剂"农达"除草后药物灭螺的效果及其可行性.方法选择3段有螺渠,随机确定为砍草渠(人工砍草+药物灭螺)、除草剂渠(除草剂+药物灭螺)和未除草渠(药物灭螺),灭螺后3d、7d、15d、30d系统抽样查螺,计算钉螺死亡率及活螺密度.结果灭螺后砍草渠和除草剂渠钉螺死亡率均显著高于未除草渠,活螺密度明显下降;灭螺后3d砍草渠钉螺死亡率显著低于除草剂渠,但灭螺后7d、15d及30d后二渠间钉螺死亡率无明显差异.除草费用,砍草渠0.14元/m2,除草剂渠0.035元/m2.结论在山丘地区,用除草剂除草是一种有效、经济、适用的灭螺前环境处理方法,值得推广应用.     

Studies on common antigenicities between the Belo Horizonte strain, Brazil of Schistosoma mansoni eggs and Biomphalaria snails by immunoelectrophoresis.

Immunoelectrophoretic studies of common antigenicities were carried out by using rabbit sera immunized against the Belo Horizonte strain of Schistosoma mansoni eggs and crude antigens of Biomphalaria snails and vice versa. With regard to common antigenicities between S. mansoni eggs and Biomphalaria snails, S. mansoni eggs produced 4 to 5 bands with Biomphalaria glabrata pigmentado, 3 to 4 bands with B. glabrata albino and only 1 band with B. straminea. In our laboratory, the infection rate of S. mansoni miracidia to B. glabrata pigmentado was 64.3% and 55.0% for B. glabrata albino, but B. straminea was not found to be susceptible to S. mansoni miracidia. It was observe that more bands were seen between S. mansoni egg and suitable hosts. Biomphalaria snail crude antigens were fractionated by Sephadex G-100 column, and each fraction antigen was tested with anti-S. mansoni egg sera by immunoelectrophoresis. As results, three fractions were collected form each snail strains. The common antigenicities between fractionated antigens from Biomphalaria snails crude antigens and anti-S. mansoni egg sera mostly existed in the first fraction and they were estimated to have molecular weights over 45,000.     

The control of the schistosome-transmitting snail Biomphalaria glabrata by the plant Molluscicide Euphorbia splendens var. hislopii (syn milli Des. Moul): a longitudinal field study in an endemic area in Brazil

Under laboratory conditions, latex from Euphorbia splendens has shown promise as a plant molluscicide for control of Biomphalaria species, intermediate hosts for Schistosoma mansoni. The purpose of this study was to evaluate its efficiency under field conditions. Application of filtered latex at 12 ppm to one stream in an endemic rural area in Minas Gerais state, Brazil, in September 1995, did result in a reduction in snail density as compared to an untreated stream but the snail population recovered quickly. However, two applications with a two-week interval of unfiltered E. splendens latex at 5 ppm in November 1996 in the same stream resulted in complete disappearance of B. glabrata and snails did not reappear until the 14th month after the applications. In the control stream, without treatment, the snails were found during all months. Laboratory studies confirmed that unfiltered latex is a more potent molluscicide than filtered latex. Considering the advantages of the latex such as its low toxicity to other aquatic animals and its photobiodegradability, as well as the simple method of application, this natural product is promising as an effective molluscicide.     

氯硝柳胺泥敷灭螺土壤残留药物对钉螺和鱼类的毒性

目的观察氯硝柳胺泥敷灭螺后土壤残留药物的持续灭螺效果和对鱼类的毒性。方法选择3个试验点开展氯硝柳胺泥敷灭螺,设0、4、6、8、10g/m^2剂量,灭螺后7、15、30、90、180d将试验药泥取回实验室,配制成各种浓度的溶液,放入活螺和活鱼;现场将水引入试验沟渠,各组筑坝隔离,投放活螺和活鱼。观察室内和现场试验钉螺和鱼的死亡情况。结果残留药物灭螺试验,泥敷15d时室内和现场试验平均钉螺死亡率分别为29.64%和60.00%,30d时室内试验平均钉螺死亡率16.07%,钉螺死亡率随时间增加而降低（χ^2=207.578,P〈0.05）。残留药物鱼毒试验,泥敷15d时室内和现场试验鱼死亡率分别为5.83%和14.17%,表明钉螺死亡率高于鱼类。结论氯硝柳胺泥敷灭螺1月内环境残留药物仍具有一定的灭螺作用;泥敷灭螺15d后环境残留药物对鱼类的毒性已明显减小。     

Immunoelectrophoretic study on common antigens of S?o Louren?o da Mata and Belo Horizonte strains of Schistosoma mansoni adult worms and Biomphalaria snails.

Immunoelectrophoretic studies on common antigens were carried out by using rabbits sera immunized against S?o Louren?o da Mata and Belo Horizonte strains of Schistosoma mansoni adult worms and antigens of Biomphalaria glabrata pigmented (Jaboat?o--PE); B. glabrata albino (Belo Horizonte--MG) and B. straminea (S?o Louren?o da Mata, PE). Furthermore, the reverse approach was proceeded, namely, sera anti Biomphalaria snails produced in rabbits were tested against both strains of Schistosoma adult worm antigens. The analysis of the common antigens between the SLM strains of S. mansoni adult worm and B. glabrata pigmented showed 8 to 9 precipitin bands, 3 bands with B. glabrata albino and only 1 band with B. straminea crude extracts. On the other hand, the BH strain of S. mansoni adult worm antisera produced 6 to 7 bands with B. glabrata pigmented, 5 bands with B. glabrata albino and 1 band with B. straminea antigenic extract. Biomphalaria snails crude extracts were fractionated by Sephadex G-100 column and three fractions were collected from each snail strain. The fractions were tested with anti SLM and BH strains of S. mansoni adult worm sera by immunoelectrophoresis. The common antigens fractionated from Biomphalaria snails crude extracts and those found for both strains of S. mansoni adult worm mostly existed in the first fraction and they were estimated to have molecular weight over 158,000 daltons. In our laboratory, it was found a relationship between the antigenic similarities and experimental infection rates of S. mansoni towards Biomphalaria snails so that more bands were seen with increasing infection rates of S. mansoni.     

Toxicology of a potential molluscicide derived from the plant Solanum xanthocarpum: a preliminary study

A potential molluscicidal extract, obtained from the indigenous Chinese plant Solanum xanthocarpum (Schrad. and Wendl), was tested for toxicity against snails and fish in static, acute-toxicity tests. The extract had a significant effect on mature and young snails of the amphibious Asian freshwater prosobranch Oncomelania hupensis (Gredler) and also on mature specimens of the freshwater pulmonate snails Biomphalaria glabrata (Say) and Lymnaea stagnalis (Linnaeus). The minimum dose that produced 100% mortality of snails exposed for 48h, 4.321mg/litre, is much less than the threshold, of 100mg/litre, set for a potential molluscicide by the World Health Organization. In contrast, the minimum concentration producing 100% mortality in the fish Gobiocypris rarus (Ye and Fu) was 17.28mg/litre. The extract also limited the extent of water-leaving by snails exposed to it, an important feature for the control of amphibious snails. This extract thus represents a promising plant-derived molluscicide which is worthy of further investigation.     

Short report: Schistosoma mansoni miracidia are killed by the defense system of an Argentine strain of Biomphalaria straminea.

Biomphalaria straminea snails from Argentina fail to shed cercariae even if exposed to high doses of Schistosoma mansoni EC miracidia. Alternative explanations for this failure are that miracidia are unable to penetrate the snail's epithelium or that the miracidia are killed by the snail's defense system. To discriminate between these 2 possibilities, B. straminea snails were individually exposed to increasing doses of miracidia. Susceptible B. glabrata were used as controls. Exposed snails were fixed 12 hr after exposure, and histological sections of the whole specimens were examined. Miracidia were seen to penetrate the epithelium of B. straminea and B. glabrata at similar rates (14.7%), independent of the exposure level. Regardless of the miracidial dose, 94% of the penetrating miracidia appeared encapsulated by the B. straminea defense system, whereas in B. glabrata, only 42% of the miracidia underwent encapsulation. These results show that resistance of B. straminea to S. mansoni EC strain is due to an efficient defense system that destroys miracidia once they have penetrated.     

云南省洱源县节水灌溉工程控制血吸虫病效果

目的 目的 评价云南省洱源县节水灌溉血防工程控制血吸虫病效果。方法 方法 调查云南省洱源县节水灌溉血防工程 实施前后螺情， 收集并分析工程所在村螺情和人群血吸虫病病情指标。 结果 结果 洱源县节水灌溉工程区有螺框出现率由改 造前的10.70％下降至改造后的2.27％， 钉螺密度由0.42只/0.1 m2 下降到0.10只/0.1 m2 ， 57％的沟渠消灭了钉螺。2009年 工程所在村钉螺面积较2005年下降了49.18%， 人群血吸虫感染率下降了99.38%。 结论 结论 节水灌溉工程是消灭钉螺、 控制 血吸虫病的有效措施， 具有良好的社会和经济效益。     

The use of the shell of the cashew nut, Anacardium occidentale, as an alternative molluscacide]

Bioassays using hexanolic extracts of cashew nut shells, of Anacardium occidentale, collected in Ceará in 1972 (Sample 1) and 1987 (Sample 2) were undertaken with adult snails and egg masses of Biomphalaria glabrata, B. tenagophila and B. straminea both in the laboratory and in the field. Non extracted shells, 18.5 g, sample 1, were also tested with adult snails and egg masses of the three species. The toxicity of extract was tested with fish (Poecilia reticulata) and tadpoles. The lethal concentration, CL90, of sample 1 was from 2.0 to 2.2 ppm for adult snails of the three species. With sample 2, the CL90 was 2.0, 0.5 and 30.0 ppm for B. glabrata adults, newly hatched snails and egg mass respectively. Non extracted shells caused 40-80% mortality of adult snails, 22-35% mortality of embryos and 40-55% reduction of egg production. The hexanolic extract, sample 2, were innocuous for tadpole and fish at 2 ppm. In the field, in pools of still water treatment with 20 ppm of extract, sample 1, caused a 97.1% mortality of B. straminea and 100% mortality of B. glabrata and B. tenagophila. Using Niclosamide, at 3 ppm, 100% mortality of the three species occurred.     

Schistosoma mansoni infection in diapausing Biomphalaria glabrata snails: studies of temperature and genetic influences on diapausing behavior.

Snails that are capable of undergoing diapause can circumvent unfavorable environmental conditions, including long periods of drought. Studies were performed to investigate possible temperature and/or genetic factors that may trigger lamella formation and diapausing behavior. The influence of diapause in Biomphalaria glabrata snails on susceptibility to Schistosoma mansoni infection and levels of cercarial production was also investigated. Rearing temperatures of 23 degrees C or higher did not induce lamella formation or diapause, regardless of the parental phenotype. However, substantial percentages of progeny from lamellated or lamellated/diapausing parental snails developed lamellae at 18 degrees C and underwent diapause. Only a small percentage of offspring from nonlamellated parents formed lamellae at this temperature. Juvenile snails exposed just prior to diapause, or immediately following a diapause period of three weeks, were highly susceptible to infection by S. mansoni miracidia. Snails that underwent diapause produced comparable or only slightly fewer cercariae than did nondiapausing snails. These studies indicate that diapause in B. glabrata does little to decrease a snail's ability to act as an intermediate host for S. mansoni or to interrupt the development of the parasite. For these reasons, we believe that greater attention should be given to diapausing snail populations when planning field surveys or mollusciciding programs.     

Identification of snails infected with schistosomes by ELISA employing monoclonal antibodies: Schistosoma mansoni in laboratory snails (Biomphalaria glabrata) and in field snails (Biomphalaria pfeifferi) from Kenya

An enzyme-linked immunosorbent assay (ELISA) employing monoclonal antibodies was used for detecting Schistosoma mansoni antigens in hemolymph of laboratory snails (Biomphalaria glabrata) in Kenya. Infected laboratory snails shedding cercariae were differentially identified by ELISA from uninfected snails with 100% sensitivity and specificity. Prepatent infections were detected by ELISA from 2 weeks after exposure to miracidia. Thus, ELISA revealed infection 3 weeks before maximal patency was reached (5-6 weeks post-exposure). Infected field snails (B. pfeifferi) shedding cercariae were differentially identified by ELISA, with 100% sensitivity and specificity, from uninfected field snails and from snails naturally infected with other trematodes (echinostomes and strigeids). Prepatent infections with S. mansoni were readily identified by ELISA in field snails. A case is demonstrated where infection rate, as determined by shedding test alone, was 9.8%, whereas the combined figure of prepatent and patent infection rates was 22.9%     

有螺沟渠硬化后钉螺复现原因

目的 目的 了解有螺沟渠硬化后钉螺复现的影响因素, 提出改进措施, 提高沟渠硬化工程的灭螺效果。方法 方法 采用回顾性调查与现场调查相结合的方法, 收集荆门市13个血吸虫病流行区乡 （镇） 实施沟渠硬化灭螺工程和螺情资料, 统计沟渠硬化工程的灭螺效果, 分析钉螺复现的原因。结果 结果 共调查151条硬化沟渠, 71条沟渠钉螺复现, 复现沟渠条数占 47.02%。钉螺面积灭光率为78.79%。钉螺复现的主要原因为上游螺区扩散、 硬化沟渠破损、 工程前未药物灭螺和施工带入钉螺等。结论 结论 单纯硬化有螺沟渠并不能彻底消灭钉螺; 科学规划沟渠硬化工程、 工程前药物灭螺和加强工程后期维护是提高灭螺效果的关键。     

Comparative study of the fecundity and fertility of Biomphalaria glabrata (Say, 1818) and Biomphalaria straminea (Dunker, 1848) in a laboratory through self-fertilization and cross-fertilization

The aim of this study was to compare the fecundity and fertility of B. glabrata and B. straminea by cross- and self-fertilization. To attain this objective, laboratory-raised strains of B. glabrata and B. straminea were used. The former originated from natural breeding grounds in the municipality Paulista, state of Pernambuco, Brazil. The latter originated from irrigation ditches in the municipality of Petrolandia, in the same state. Snail populations of B. glabrata and B. straminea were maintained for 240 days in laboratory. Their fecundity was evaluated by noting the number of egg-masses, eggs and eggs per mass. Their fertility was evaluated by the number of viable eggs and the hatching rate. B. straminea was markedly more fecund than B. glabrata through cross- and self-fertilization, namely: greater egg-mass; higher egg production and more eggs per mass. Regarding fertility, there seemed to be no preferential period for occlusion to occur or a trend in the rhythm of producing viable eggs.     

中层取水拦螺网用于电灌站防螺的效果观察

目的评价中层取水拦螺网用于电灌站防螺的效果。方法在有螺河道肖梁河取水的王庄电灌站进水口设置中层取水拦螺网,用常规法对电灌站水源河道和灌区沟渠进行钉螺调查。对有螺水源河道和灌区有螺环境进行药物灭螺。根据钉螺面积和钉螺密度变化进行防螺效果评价。结果 2006～2011年肖梁河每年均查出钉螺,钉螺面积和钉螺密度呈显著正相关(r=0.972,P<0.01),并呈下降趋势。王庄电灌站设置中层取水拦螺网之前每年均查出钉螺,有螺面积与钉螺密度呈正相关(r=1.000,P<0.01);设置中层取水拦螺网后灌渠即未查出钉螺。结论在有钉螺扩散风险的电灌站设置中层取水拦螺网结合药物灭螺是简便有效的防控钉螺扩散模式。     

水网地区低密度钉螺自然增长情况

通过1987—1990年在无锡、如东、如皋3个市县的现场实验和河沟钉螺调查。发现低密度钉螺的消长与环境因子密切有关,只要环境适宜,即使留下1对钉螺,也能大量繁殖增长。实验沟放置有1、5和10对钉螺的螺笼经3年后,钉螺密度各增长了171.9倍、69.5倍和28.4倍。其螺口数分别增长了354倍、135倍和75倍,其中2条积水沟的1对钉螺组螺口数增长543和426.5倍。在现场1条水沟钉螺密度增长了34倍,1条河钉螺密度没有增长,但都没有自然消亡。提示当“基本消灭”或“消灭”以后,应重视低密度钉螺的清查,坚持长期监测,一旦发现钉螺,要及时杀灭。     

江滩喷洒氯硝柳胺悬浮剂灭螺效果纵向观察

目的评价氯硝柳胺悬浮剂（SCN）在江滩地区连续应用的灭螺效果,为江滩地区长期应用SCN灭螺提供依据。方法选择江苏省扬中市有螺江滩作为灭螺现场,每年按SCN总剂量6-8g/m2进行喷洒灭螺,并对螺情进行调查,考核连续4年应用SCN的灭螺效果。结果2004-2007年江滩灭螺前活螺平均密度分别为6.00、4.25、2.04只/0.1m^2和1.95只/0.1m^2;灭螺后活螺平均密度分别为0.86、0.86、0.23只/0.1m^2和0.16只/0.1m^2;灭螺后活螺密度逐年下降,2004-2007年活螺密度下降率分别为85.67%、79.76%、88.49%和91.78%。2007年灭螺后较2004年灭螺前活螺框出现率由73.46%降为9.66%,下降了86.85%;活螺平均密度由6.00只/0.1m^2降为0.16只/0.1m^2,下降了97.33%。结论经过连续4年使用SCN喷洒灭螺,钉螺密度显著下降,灭螺效果稳定可靠。SCN适用于江滩地区长期大规模灭螺。     

南京市浦口区通江河道水利血防工程结合药物灭螺控制钉螺效果

目的评价通江河道水利血防工程结合药物灭螺控制钉螺效果。方法选择南京市浦口区朱家山河、七里河和高旺河为研究对象,采用资料回顾和现场调查方法,评估通江河道水利血防工程结合药物灭螺控制钉螺效果。结果通江河道实施水位控制、砼护坡水利血防工程及药物灭螺后,工程段钉螺即消除,内陆灌区未发生钉螺扩散,河口外江滩虽然仍保持有钉螺孳生,但钉螺密度大幅下降至1.0只/0.1 m~2以下。结论通江河道水位控制、砼护坡结合药物灭螺综合措施可稳定有效地控制和消除钉螺孳生,阻止钉螺向内陆扩散。