Differential susceptibility of male and female Oncomelania hupensis quadrasi infected with Schistosoma japonicum

Laboratory-reared male and female Oncomelania hupensis quadrasi were exposed to infection with Schistosoma japonicum. In three of four trials, infection rates in female snails (30.5–68.0%) were higher than in males (8.6–28.6%). Higher cercarial production in females may be accounted for by male-female size difference, and presumably by the availability of more nutrients in females as a result of ovarian tissue breakdown. Male and female snails were individually exposed to 20 miracidia, fixed 3–72 h post-exposure and serially sectioned to check for encapsulated and nonencapsulated primary sporocysts (ps). In 23 female (65.2%) and 12 male (39.3%) snails, ps were all unencapsulated. Six male snails (17.6%) showed 100% ps encapsulation. Among the 12 females and 16 males with both negative and positive host-tissue response, encapsulated ps in females varied from 7.1 to 50.0% and 20.0 to 71.4% in males. Distribution of encapsulated and non-encapsulated ps in both sexes suggests that males are more resistant to infection by their encapsulation reaction. Whether resistance in O. h. quadrasi to S. japonicum is genetically determined warrants further study.     

Functional properties of hemocyanin from Oncomelania hupensis, the intermediate host of Schistosoma japonicum

The gastropod mollusc, Oncomelania hupensis is a unique intermediate host for the human parasite Schistosoma japonicum. It is a primary factor for the epidemic of schistosomiasis and its distribution is consistent with the epidemic area of schistosomiasis. Here we report the functional properties of hemocyanin of O. hupensis (OhH), a copper-containing respiratory protein which was isolated from its hemolymph and purified by ammonium sulfate fractionation and ultracentrifugation. We identified the protein characters including UV absorption at 340 nm, copper content and quaternary structure. Furthermore, by induction of phenoloxidase and enzyme-linked immunosorbent assay we show that OhH exhibited o-diphenoloxidase activity after limited proteolysis, and shared carbohydrate epitopes with glycoconjugates of S. japonicum.     

Comparative Phylogenetic Studies on Schistosoma japonicum and Its Snail Intermediate Host Oncomelania hupensis: Origins,Dispersal and Coevolution

Background

Schistosoma japonicum causes major public health problems in China and the Philippines; this parasite, which is transmitted by freshwater snails of the species Oncomelania hupensis, causes the disease intestinal schistosomiasis in humans and cattle. Researchers working on Schistosoma in Africa have described the relationship between the parasites and their snail intermediate hosts as coevolved or even as an evolutionary arms race. In the present study this hypothesis of coevolution is evaluated for S. japonicum and O. hupensis. The origins and radiation of the snails and the parasite across China, and the taxonomic validity of the sub-species of O. hupensis, are also assessed.

Methodology/Principal Findings

The findings provide no evidence for coevolution between S. japonicum and O. hupensis, and the phylogeographical analysis suggests a heterochronous radiation of the parasites and snails in response to different palaeogeographical and climatic triggers. The results are consistent with a hypothesis of East to West colonisation of China by Oncomelania with a re-invasion of Japan by O. hupensis from China. The Taiwan population of S. japonicum appears to be recently established in comparison with mainland Chinese populations.

Conclusions/Significance

The snail and parasite populations of the western mountain region of China (Yunnan and Sichuan) appear to have been isolated from Southeast Asian populations since the Pleistocene; this has implications for road and rail links being constructed in the region, which will breach biogeographical barriers between China and Southeast Asia. The results also have implications for the spread of S. japonicum. In the absence of coevolution, the parasite may more readily colonise new snail populations to which it is not locally adapted, or even new intermediate host species; this can facilitate its dispersal into new areas. Additional work is required to assess further the risk of spread of S. japonicum.     

Transplantation of Schistosoma japonicum daughter sporocysts in Oncomelania hupensis

Schistosoma japonicum daughter sporocysts obtained from infected Oncomelania hupensis hupensis were successfully transplanted to parasite-free O. hupensis hupensis. Survival and infection rates of recipient snails were 80% and 75% respectively. Intramolluscan development of transplanted daughter sporocysts in recipient snails appears to proceed in a similar manner as those reported for transplanted S. mansoni and S. haematobium in their respective snail intermediate hosts. Complete colonization of the digestive gland of recipient snails by sporocysts was observed 80 days after transplantation. Cercarial production during a 10-day observation from recipient snails was characterized by periods of high and low and irregular daily emissions. The average daily cercarial production was 150 per snail. Cercariae produced by recipient snails were infective to mice. Of those cercariae exposed to mice, approximately 30% developed to adult schistosomes. These results have definitive utility in the maintenance of S. japonicum in the laboratory.     

Vaccine potential of hemocyanin from Oncomelania hupensis against Schistosoma japonicum

Hemocyanin, a giant oxygen transport protein which is usually found in many arthropods and mollusks was isolated and purified from Oncomelania hupensis. In this study, we showed that Oncomelania hupensis hemocyanin (OhH) shared carbohydrate epitopes with different developmental stages of Schistosoma japonicum (Cercaria, Schistosomulum, Adult worm and Egg) and exhibited serological cross-reaction with these stages of S. japonicum immune sera, which had a potential for use in diagnostic and therapeutic studies of schistosomasis. OhH was used as a vaccine in combination with Freund's adjuvant to evaluate the induction of immune responses and protection against S. japonicum infection in mice. Mice immunized with OhH induced a Th1 type of immune responses. Strong protection against S. japonicum were observed in adult worm and egg burdens after 42 days post-challenge, which showed a significant worm reduction of 52.5% and egg reduction of 69.2% compared to the control groups, respectively. These results indicated that OhH was a potential candidate to compose an anti-schistosome vaccine.     

Distinct Genetic Diversity of Oncomelania hupensis,Intermediate Host of Schistosoma japonicum in Mainland China as Revealed by ITS Sequences

Background

Oncomelania hupensis is the unique intermediate host of Schistosoma japonicum, which causes schistosomiasis endemic in the Far East, and especially in mainland China. O. hupensis largely determines the parasite''s geographical range. How O. hupensis''s genetic diversity is distributed geographically in mainland China has never been well examined with DNA sequence data.

Methodology/Principal Findings

In this study we investigate the genetic variation among O. hupensis from different geographical origins using the combined complete internal transcribed spacer 1 (ITS1) and ITS2 regions of nuclear ribosomal DNA. 165 O. hupensis isolates were obtained in 29 localities from 7 provinces across mainland China: lake/marshland and hill regions in Anhui, Hubei, Hunan, Jiangxi and Jiangsu provinces, located along the middle and lower reaches of Yangtze River, and mountainous regions in Sichuan and Yunnan provinces. Phylogenetic and haplotype network analyses showed distinct genetic diversity and no shared haplotypes between populations from lake/marshland regions of the middle and lower reaches of the Yangtze River and populations from mountainous regions of Sichuan and Yunnan provinces. The genetic distance between these two groups is up to 0.81 based on Fst, and branch time was estimated as 2–6 Ma. As revealed in the phylogenetic tree, snails from Sichuan and Yunnan provinces were also clustered separately. Geographical separation appears to be an important factor accounting for the diversification of the two groups of O. hupensis in mainland China, and probably for the separate clades between snails from Sichuan and Yunnan provinces. In lake/marshland and hill regions along the middle and lower reaches of the Yangtze River, three clades were identified in the phylogenetic tree, but without any obvious clustering of snails from different provinces.

Conclusions

O. hupensis in mainland China may have considerable genetic diversity, and a more complex population structure than expected. It will be of significant importance to consider the genetic diversity of O. hupensis when assessing co-evolutionary interactions with S. japonicum.     

Malic dehydrogenase patterns in different strains of Schistosoma japonicum and subspecies of Oncomelania hupensis.

Malic dehydrogenase (MDH) of the Formosan Philippine and Indonesian Strains of Schistosoma japonicum and 3 subspecies of snails, Oncomelania hupensis formosana, O. h. quadrasi, and O. h. lindoensis were identified by disc electrophoresis with 10.5% acrylamide gel columns using tris-malic buffer. Male worm extracts of S. japonicum demonstrated 3, 2, and 2 clear MDH patterns and female worm extracts showed patterns of 2, 1 and 1 for the Formosan, Philippine and Indonesian strains of the parasite, respectively. MDH patterns were the same for all 3 subspecies of snails; one major and one minor band being found in all.     

Genetic diversity and structure of Oncomelania hupensis hupensis in two eco-epidemiological settings as revealed by the mitochondrial COX1 gene sequences

Background

Oncomelania hupensis hupensis is the only intermediate host of Schistosoma japonicum, the causative agent of schistosomiasis in China and is therefore of significant medical and veterinary health importance. Although tremendous progress has been achieved, there remains an understudied area of approximately 2.06 billion m² of potential snail habitats. This area could be further increased by annual flooding. Therefore, an understanding of population genetics of snails in these areas may be useful for future monitoring and control activities.

Methods and results

We sampled snails from Hexian (HX), Zongyang (ZY) and Shitai (ST) in Anhui (schistosomiasis transmission control), and from Hengtang (HT), Taicang (TC), Dongsan (DS) and Xisan (XS) in Jiangsu (schistosomiasis transmission interrupted), downstream of Anhui. ST, DS and XS are classified as hilly and mountainous areas, and HX, ZY, TC and HT as lake and marshland areas. The mitochondrial cytochrome c oxidase subunit I gene were sequenced. Out of 115 snails analyzed, 29 haplotypes were identified. We observed 56 (8.72%) polymorphic sites consisting of 51 transitions, four transversions and one multiple mutational change. The overall haplotype and nucleotide diversity were 0.899 and 0.01569, respectively. Snail populations in Anhui had higher genetic diversity than in Jiangsu. 73.32% of total variation was distributed among sites and 26.68% within sites. Snails were significantly separated according to eco-epidemiological settings in both network and phylogenetic analyses.

Conclusion

Our results could provide important guidance towards assessing coevolutionary interactions of snails with S. japonicum, as well as for future molluscan host monitoring and control activities.

     

三峡库区重庆段钉螺孳生条件

三峡工程的修建使得长江水生环境发生了变化,同时水库的阶段性蓄、放水使得阶段性淹没的江洲滩增加,更加有利于挺、浮水植物的繁殖,从而可能形成适合日本血吸虫(Schistosoma japonicum)的惟一中间宿主———钉螺(Oncomelania hupensis)的生长环境。本文在钉螺生活习性的基础上,结合数字高程模型(DEM)和相关的气象资料以及水库的蓄放水规律,从气候、淹没时间、植被、水库的蓄放水时间等角度对三峡库区钉螺孽生条件进行了分析。从气候上看,阶段性淹没区能够满足钉螺生长的需要;然而,水库冬季蓄水、夏季放水的周期与钉螺生长需求并不完全相同,尤其是冬季的高水位对钉螺生长十分不利。因此,水库的修建并不一定会造成钉螺的孽生和血吸虫的流行。     

几种杀螺细菌的筛选与功效研究

湖北钉螺是日本血吸虫的唯一中间宿主,生物杀螺具有环保、成本较低以及对钉螺定向特异的优点。从鄱阳湖草洲土壤及病螺体内分离出4株对钉螺具有高毒性作用的细菌。革兰氏染色和显微镜观察表明,一株为芽孢杆菌,其余3株均为革兰氏阴性杆菌。16srDNA扩增及序列比对鉴定其种属类型,结果显示分别为Enterobactersp．、B．cereus、S．putrefaciens和Aeromonassp．。杀螺研究结果表明,4株细菌的发酵液、发酵上清液和菌体对钉螺均表现出不同程度的毒杀作用,其中S．putrefaciens和Aeromonassp．的杀螺效果最好,72h发酵液和发酵上清液对钉螺的毒杀作用分别达100％和95％以上。各细菌发酵上清SDS-PAGE结果发现了丰富蛋白带,推测这些蛋白中存在对钉螺具有毒杀功效的组分。     

Parasitological studies at a new breeding area of Oncomelania hupensis chiui in Taipei county, Taiwan.

Oncomelania hupensis chiui was found at the Jui-Ping area, Linkow District, Taipei County, Taiwan, which is located on the north coast of the island approximately 10 km of the mouth of the Tamasui River. The habitat of the snails at this area is similar to the type locality at Alilao, on the slope of the hills along of coast. The snails from this new breeding area, are similar to the Alilao snails, and are highly susceptible to the infection with geographic strains of Schistosoma japonicum including the Changhua, Ilan, Japanese, Philippine and Chinese strains. Examinations of 7,758 snails and intradermal tests on 736 inhabitants along with stool examinations of 622 people indicated that there was no evidence of the presence of Schistosoma japonicum at this area. Results obtained from stool examination demonstrated high prevalence of hookworm infection (53.4%) and relatively low infection rates of Asearis lumbricoides (37.0%) and Trichuris trichiura (14.1%). The protozoan infections were low in general. A single Scotch-tape technique for Enterobius vermicularis among 499 school children yielded a 55.7% infection rate.     

中国灭螺技术的研究进展

本文就我国在化学药物灭螺、环境改造灭螺、利用食螺动物和靶螺竞争生物灭螺及植物灭螺的研究进展进行了综述,以期为灭螺技术的开发和应用提供依据.     

樟树水浸液的灭螺效果

研究了新鲜樟树的茎皮、根皮和叶的水浸液对钉螺的杀灭效果。结果表明：通过一定时间的处理,樟树水浸液对钉螺有明显的毒杀作用。其中,0．5％以上的茎皮和根皮的水浸液对钉螺具有35％-100％的毒杀作用;处理时间在72h时,死螺率可达80％-100％。0．5％的樟树根皮水浸液浸泡72h时,死螺率为95％;1％的樟树根皮水浸液浸泡72h时,死螺率为100％。当用同种水浸液浸泡时,钉螺死亡率随水浸液浓度的增加而升高;随着浸泡时间的延长,钉螺的死亡率也升高。     

夹竹桃灭钉螺效果初报

1　引　　言在防治血吸虫病的过程中 ,人们一直致力于消灭其唯一中间宿主钉螺 .近年来长江中下游生态环境破坏严重 ,一些地方有螺面积扩大 ,疫情回升 .常用化学药物灭螺法虽有较明显的灭螺效果 ,但也造成了严重的环境污染 .90年代以来生物灭螺开始成为比较活跃的研究领域 ,在筛选灭螺植物 ,提取植物灭螺活性成分和利用植物他感作用灭螺等方面已取得了许多成绩[1～ 4 ,7,8] .目前 ,植物灭螺难以推广的主要问题在于利用新鲜植物材料灭螺常需要较高的浓度 ,而原料来源往往有限 ;提取植物灭螺活性成分制作灭螺剂的成本较高 ,难以广泛应用 .因此 …     

Induction of resistance in Oncomelania hupensis nosophora against Schistosoma japonicum, but not against Paragonimus ohirai, using irradiated miracidia

Oncomelania hupensis nosophora snails sensitized with X-irradiated Schistosoma japonicum miracidia demonstrated resistance against a following challenge infection with non-irradiated homologous miracidia. The resistance in O. h. nosophora against S. japonicum was acquired within 1 day of sensitization, and it was strongest in a group challenged at an interval of 3 days. The resistance persisted for at least 4 weeks. Histological examinations revealed amoebocyte accumulation around the challenged S. japonicum sporocysts. On the other hand, when O. h. nosophora sensitized by exposure to X-irradiated P. ohirai or S. japonicum miracidia were subsequently challenged with normal P. ohirai miracidia, no resistance was observed, although they expressed the resistance against heterologous S. japonicum infection.     

樟树水浸液对钉螺的生态毒理学效应

用樟树(Cinnamomum camphora)新鲜根皮、茎皮、叶为材料,设置1%、0.5%、0.1%、0.05%4个不同浓度梯度的水浸液处理钉螺,以清水和1 mg/L浓度的氯硝柳胺溶液为对照,统计钉螺死亡率,并分析钉螺过氧化氢酶(CAT)和过氧化物酶(POD)活性及采用透射电镜分析亚显微结构损伤情况。结果表明:(1)樟树各部分的水浸液均有很好的灭螺效果。钉螺死亡率随处理浓度的增加和时间的延长呈上升趋势,0.5%—1.0%以上的樟树根皮、茎皮、叶水浸液均可达到100%的毒杀钉螺致死效果,与1 mg/L氯硝柳胺溶液的灭螺效果相当;灭螺效果顺序依次为:根皮茎皮叶。(2)在处理初期,钉螺体内过氧化氢酶和过氧化物酶活性明显增强,但随处理时间延长,其活性急剧降低;过氧化物酶同工酶谱显示,处理24—48 h后钉螺酶活高于对照组,处理72—96 h后酶活最强,而处理120 h酶活则大大减弱。(3)钉螺肝细胞亚显微结构观察表明,随处理时间的延长,线粒体、内质网、细胞核等结构损伤越来越严重。这些结果表明樟树水浸液对钉螺肝脏造成过氧化伤害和细胞器结构损伤,具有很好的杀螺效果,可作为生态工程抑螺林树种。     

湘江长沙段洲滩钉螺防治后的种群动态

采用以系统抽样结合环境抽查的查螺方法,对湘江长沙段洲滩进行连续6年的螺情调查.2003-2008年跟踪调查了湘江长沙段24个洲滩,其中20个洲滩有钉螺分布,占洲滩总数的83.3%,4个洲滩从未查见钉螺.活螺洲滩数分别占当年调查洲滩的62.50%、66.67%、66.67%、70.83%、33.33%、37.50%;2008年与2003年相比,活螺洲滩数下降了40.00%,有螺框出现率、钉螺平均密度、活螺率分别下降了99.10%、99.74%、51.09%.经统计学处理,各洲滩有螺框出现率(Z=91.56,P<0.01)、活螺率(Z=65.13,P<0.01)不相同,但年度下降趋势明显.在20个有螺洲滩中,有感染性钉螺分布的洲滩5个,占有螺洲滩总数的25.00%;有感染性钉螺分布的洲滩逐年减少,平均密度和感染率逐年降低,2007-2008年所有洲滩均无感染性钉螺分布.湘江长沙段有螺洲滩采取的各种防治措施中,药物与环改灭螺相结合的效果远好于单纯的药物灭螺.各种环改灭螺措施中,又以抬洲降滩、翻耕垦种的灭螺效果更持久,更彻底.2007、2008年有螺洲滩数、钉螺总数急剧减少,有螺框出现率、活螺率大幅度下降还町能与水位和气候有关.湘江长沙段洲滩的螺情得到了较好的控制.     

植物内生真菌杀螺活性菌株筛选

分别从醉鱼草和水菖蒲中分离出99、103株内生真菌,按照WHO杀螺剂浸泡试验法观察不同内生真菌以及不同浓度发酵液杀螺效果.用河虾急性毒性试验评价其对非靶水生生物毒性.结果表明LL3026、S38、S21菌株发酵液有较高的杀螺活性,发酵液浓度为10%时,钉螺死亡率为100.0%;对河虾急性毒性较小.     

植物颗粒剂对钉螺毒杀效果的研究

将3种药用植物材料分别粉碎后与淀粉、明胶配合制成直径2～3mm的植物颗粒剂用于灭钉螺试验,结果表明,钉螺取食3种颗粒剂后,24h死亡率分别达到92.5％～100％.其毒杀效果明显优于相同植物的其它灭螺方法,对钉螺的致死时间比氯硝柳胺化学灭螺剂(1×10-3g·L-1)提前12～24h.用3种植物颗粒灭螺剂进行野外灭螺实验,钉螺死亡率最高可达61.5％.