Molecular Characterization of Rotifers and Their Potential Use in the Biological Control of Biomphalaria.

Background: Schistosomiasis is one of the most important tropical parasitic diseases worldwide. Biomphalaria straminea, the intermediate host of Schistosoma mansoni, has invaded and spread to Southern China since 1974 and may pose enormous threats to public health. Controlling intermediate host snails is an effective strategy in schistosomiasis intervention. However, the only effective chemical molluscicide, niclosamide, currently recommended by WHO may cause environmental pollution, loss of biodiversity, and high costs. Thus, to counter intermediate hosts, a sustainable and environmentally friendly tool is urgently needed. Here, we conducted field investigations to collect and identify a potential snail competitor rotifer and evaluated its molluscicide effect. Results: In this study, we collected two samples of rotifers from Shenzhen. We found both red and black phenotypic B. straminea snails at the sampling sites. We identified the rotifer population as a species of the genus Philodina according to the amplification and phylogenetic analysis results of coxI gene. We found that rotifer exposure did not significantly affect the hatching rate of B. straminea eggs but promoted the killing of juvenile snails. Meanwhile, rotifer exposure did not significantly alter the fecundity of B. straminea quantified by the number of eggs per egg mass, the number of egg masses per snail, and the number of eggs per snail; but the snails exposed to rotifers showed lower fecundity performance than the control snails. Importantly, rotifer exposure could significantly affect the development of juvenile B. straminea, showing a smaller shell diameter of the exposed snails than that of the control snails. In addition, rotifer exposure affected the life span of B. straminea snails, showing a 16.61% decline in the average life span. After rotifer exposure, the S. mansoni-infected B. straminea snails died significantly faster than those without rotifer exposure. Similar findings were observed in S. mansoni-infected Biomphalaria glabrata snails. These results implied that rotifer exposure significantly promoted the mortality of S. mansoni-infected B. straminea and B. glabrata. Conclusions: Our study demonstrated the potential molluscicide effect of rotifers on intermediate hosts under laboratory conditions. Our findings may provide new insights into the development of biocontrol strategies for snail-borne disease transmission.

Extended survival and reproductive potential of single-sex male and female Schistosoma japonicum within definitive hosts.

Schistosomiasis is caused by dioecious helminths of the genus Schistosoma. Recent work indicated that unpaired female and male schistosomes can survive within their definitive host for at least 1 year, although the viability or fertility of these worms after subsequent pairing remained untested. We performed two experiments on laboratory mice, one with female Schistosoma japonicum exposure first and male schistosomes second and another vice versa. After surviving as single-sex unpaired forms for up to 1 year, 58.5% of male and 70% of female schistosomes were able to mate and produce viable eggs. This highlights an additional biological challenge in achieving elimination of schistosomiasis.

The potential risk of Schistosoma mansoni transmission by the invasive freshwater snail Biomphalaria straminea in South China.

Schistosomes infect more than 200 million people worldwide, and globally, over 700 million people are at risk of infection. The snail Biomphalaria straminea, as one of the intermediate hosts of Schistosoma mansoni, consecutively invaded Hong Kong in 1973, raising great concern in China. In this study, a malacological survey was conducted over a period of four years, and investigations were performed on the mechanism of susceptibility of B. straminea to S. mansoni. B. straminea was investigated in China from 2014 to 2018. Out of 185 investigated sites, 61 were positive for stages of black B. straminea (BBS), which shows pigmented spots. Twenty of the 61 sites were positive for red B. straminea (RBS), which is partially albino and red colored. Phylogenetic analyses based on cox1 and 18S rRNA sequences demonstrated that both phenotypes were clustered with Brazilian strains. No S. mansoni infections were detected in field-collected snail. However, in laboratory experiments, 4.17% of RBS were susceptible to a Puerto Rican strain of S. mansoni, while BBS was not susceptible. The highest susceptibility rate (70.83%) was observed in the F2 generation of RBS in lab. The density of RBS has increased from south to north and from west to east in Guangdong since 2014. Five tyrosinase tyrosine metabolism genes were upregulated in BBS. Transcriptome comparisons of RBS and BBS showed that ficolin, C1q, MASP-like, and membrane attack complex (MAC)/perforin models of the complement system were significantly upregulated in BBS. Our study demonstrated that B. straminea is widely distributed in Hong Kong and Guangdong Province, which is expanding northwards very rapidly as a consequence of its adaptation to local environments. Our results suggest that B. straminea from South China is susceptible to S. mansoni, implying the high potential for S. mansoni transmission and increased S. mansoni infection risk in China.

A meta-analysis of infection rates of Schistosoma japonicum in sentinel mice associated with infectious waters in mainland China over last 40 years.

BACKGROUND: Schistosomiasis japonica is a zoonotic parasitic disease. After nearly 70 years of control efforts in China, Schistosomiasis transmission has been reduced to a much lower level. The absence or near absence of infections in humans or livestock, based on traditional fecal and serological tests, has made the targets and priorities of future control efforts difficult to determine. However, detection of schistosome cercariae in waters using sentinel mice could be an alternative way of identifying remaining foci of infection, or even serve as a tool for evaluation of control efficacy. This method has been employed in China over last forty years. We therefore performed a meta-analysis of the relevant research to investigate if infections in sentinel mice mirror the ongoing trend of schistosomiasis transmission in China. METHODS: We conducted a meta-analysis of studies reporting infection rates of S. japonicum in sentinel mice in China before Sep 1, 2018 in accordance with the PRISMA guidelines. We retrieved all relative studies based on five databases (CNKI, WanFang, VIP, PubMed and Web of Science) and the reference lists of resulting articles. For each individual study, the infection rate in sentinel mice is presented together with its 95% confidence interval (CI). Point estimates of the overall infection rates and their 95% CIs were calculated. Subgroup analyses were performed according to study periods, seasons or regions. RESULTS: We identified 90 articles, including 290 studies covering eight endemic provinces. The overall rate in sentinel mice was 12.31% (95% CI: 10.14-14.65%) from 1980 to 2018. The value of 3.66% (95% CI: 2.62-4.85%) estimated in 2004 to 2018 was significantly lower than in 1980 to 2003 (22.96%, 95% CI: 19.25-26.89%). The estimate was significantly higher in the middle and lower reaches than in the upper reaches of the Yangtze River. The highest estimates were obtained in Hunan (30.11%, 95% CI: 25.64-34.77%) followed by Anhui (26.34%, 95% CI: 12.88-42.44%) and then Jiangxi (13.73%, 95% CI: 6.71-22.56%). Unlike the other provinces in the middle and lower reaches, no significant reduction was seen in Hubei after 2003. Even in Hubei two studies carried out after 2014 reported infections in sentinel mice, although no infected snails were reported across the province. Infections were most found in April (17.40%, 95% CI: 1.13-45.49%), July (24.98%, 95% CI: 15.64-35.62%) and October (17.08%, 95% CI 5.94-32.05%). High degrees of heterogeneity were observed. CONCLUSION: This meta-analysis provides a comprehensive analysis of schistosome infection in sentinel mice across China. The estimates largely mirror the ongoing trends of transmission in terms of periods and regions. Infections were most likely to occur in April, July and October. In areas where no infected snails were reported infections in sentinel mice were still observed. Due to the presence of snails and infected wildlife, detection of schistosomes in waters using such a highly sensitive method as the deployment of sentinel mice, remains of importance in schistosomiasis monitoring. We would suggest the current criteria for transmission interruption or elimination of schistosomiasis in China be adjusted by integrating the results of sentinel mice based surveys.

Population genetics of Oncomelania hupensis snails, intermediate hosts of Schistosoma japonium, from emerging, re-emerging or established habitats within China.

Schistosomiasis remains one of the world's most significant neglected tropical diseases, second only to malaria in terms of socioeconomic impact. In 2014, China proposed the goal of schistosomiasis japonicum elimination by 2025. However, one major challenge is the widely distributed, and in certain cases potentially increasing, habitats of Oncomelania hupensis, the snail intermediate hosts of S. japonicum. Therefore, an understanding of population genetics of O. hupensis in new or re-emerged habitats, together with that of the established habitats with snail persistence, would be valuable in controlling and predicting the future transmission dynamics of schistosomiasis in China. Using nine microsatellite loci, we conducted population genetic analyses of snails sampled from one habitat where snails were detected for the first time, one (previously eliminated) habitat with re-emerged snails, and one habitat with established snail persistence. Results showed lower diversities, in terms of number of observed alleles per locus (Na), number of effective alleles per locus (NeA), observed (Ho) and expected heterozygosity (He), in snails from new or re-emerged snail habitats than from the habitat with snail persistence. The smallest effective population size was inferred in the re-emerged snail habitat, but the largest was in the new habitat rather than in the habitat with snail persistence. No bottleneck effects were detected in new or re-merged habitats. No or low sub-structure was inferred in new and persistent snail habitats. Snails from the three sites were clearly separated and low gene flow was estimated between sites. We propose that snails at the new habitat may have been introduced through immigration, whereas snails at the re-emerged habitat may be the consequence of those few snails remaining subsequently expanding through reproduction. We discuss our results in terms of their theoretical and applied implications.

Approaches being used in the national schistosomiasis elimination programme in China: a review.

Schistosomiasis japonica, caused by the human blood fluke Schistosoma japonicum, remains a major public health problem in China, although great success has been achieved. The control efforts during the past half-decade, notably the wide implementation of the new integrated strategy with emphasis on control of the source of S. japonicum infection across the country since 2004, has greatly reduced S. japonicum in humans, livestock, and intermediate host Oncomelania hupensis snails, and transmission control of schistosomiasis was achieved in China in 2015. A two-stage roadmap was therefore proposed for schistosomiasis elimination in 2015, with aims to achieve transmission interruption by 2020 and achieve disease elimination by 2025 in the country. During the last two decades, a variety of approaches, which target the epidemiological factors of schistosomiasis japonica have been developed, in order to block the transmission cycle of the parasite. These approaches have been employed in the national or local schistosomiasis control activities, and facilitated, at least in part, the progress of the schistosomiasis elimination programs. Here, we present an approach to control the source of S. japonicum infection, three new tools for snail control, three approaches for detecting and monitoring S. japonicum infection, and a novel model for health education. These approaches are considered to play a great role in the stage moving towards transmission interruption and elimination of schistosomiasis in China.

An integrated environmental improvement of marshlands: impact on control and elimination of schistosomiasis in marshland regions along the Yangtze River, China.

BACKGROUND: Schistosomiasis is a global snail-transmitted infectious disease of poverty. Transmission control had been achieved in China in 2015 after the control efforts for over 60 years. Currently, the remaining core regions endemic for Schistosoma japonicum are mainly located in the marshland and lake regions along the Yangtze River basin. METHODS: During the period from 2001 through 2015, an integrated environmental improvement of the marshlands was carried out through the implementation of industrial, agricultural and resources development projects in Yizheng County along the Yangtze River. S. japonicum infection in humans, livestock and snails was estimated by serology, stool examination, hatching technique and microscopy during the 15-year study period to evaluate the effect of the integrated environmental improvement on control and elimination of schistosomiasis. RESULTS: A 0.05% overall rate of S. japonicum infection was observed in snails during the 15-year study period, and no infected snails were detected since 2012. The overall prevalence of S. japonicum infection was 0.09% in humans during the study period, and no human infection was found since 2012. In addition, only 13 bovines were identified with S. japonicum infection in 2003 during the 15-year study period, and since 2004, no infection was found in livestock. CONCLUSION: The results of the present study demonstrate that the implementation of industrial, agricultural and water resources development projects, not only alters snail habitats in marshland regions, and promotes local economic development, which appears a win-to-win strategy to block the transmission of S. japonicum and accelerate socio-economic development along the Yangtze River.

A multidisciplinary, integrated approach for the elimination of schistosomiasis: a longitudinal study in a historically hyper-endemic region in the lower reaches of the Yangtze River, China from 2005 to 2014.

BACKGROUND: Although great success has been achieved, schistosomiasis remains a major public health concern in China, and the remaining core endemic regions are concentrated along the middle and lower reaches of the Yangtze River. In this longitudinal study, we evaluated the effectiveness of a multidisciplinary, integrated approach for schistosomiasis elimination in a historically hyper-endemic region in the lower reaches of the Yangtze River, China over the 10-year period from 2005 through 2014. METHODS: A three-step roadmap for schistosomiasis elimination was designed in the study site, and multidisciplinary, integrated interventions were implemented by the health, agriculture, water resources development, land and resources, and forestry sectors from 2005 to 2014, including chemotherapy for infected individuals, health education, management of the source of Schistosoma japonicum infection, and intermediate host snail control. The annual number of schistosomiasis patients, S. japonicum infection in humans, bovines and Oncomelania hupensis snails, and water infectivity were observed to assess the effectiveness of the multidisciplinary, integrated approach for the elimination of schistosomiasis. RESULTS: There was a tendency towards a gradual decline in both the number of schistosomiasis cases and the prevalence of S. japonicum human infection across the study period from 2005 through 2014. No S. japonicum human infection was detected since 2012, and no acute infection was seen since 2006. During the study period, no infection was found in bovines, and a 0.03% overall infection rate was observed in O. hupensis snails. Since 2009, no infected snails were identified, and the area of both snail habitats and infected snail habitats appeared a reduction over the study period. Following the 3-year multidisciplinary, integrated control, infection control was achieved, and transmission control was achieved after 6-year implementation, with all infected snails and water infectivity eliminated; in addition, the 10-year implementation resulted in interruption of schistosomiasis transmission in the study site in 2014. CONCLUSIONS: The results of the present 10-year longitudinal study demonstrate that the multidisciplinary, integrated approach is effective for the elimination of schistosomiasis as a public health problem in the lower reaches of the Yangtze River, China.

Evaluating the risk of Schistosoma mansoni transmission in mainland China.

Biomphalaria straminea, an intermediate host of Schistosoma mansoni, is predominantly distributed in the South Americas and Caribbean; however, this snail, as an invasive species, was introduced to Shenzhen, southern China, in 1981, and recent epidemiologic surveys demonstrate that the distribution of B. straminea has expanded across the Zhujiang River Basin, South China. In the presence of continuous importation of S. mansoni-infected cases, there is a growing concern about the transmission of S. mansoni in China. To evaluate the risk of S. mansoni transmission in China, we tested the compatibility of B. straminea captured from the snail habitats in southern China with S. mansoni in laboratory. We detected no S. mansoni infections in B. straminea following exposure to the parasite larvae at snail/miracidium ratios of 1:5, 1:10, 1:20, 1:40, and 1:80, while 6.7 to 66.7 % infections occurred in the control Biomphalaria glabrata depending on the ratio. The results of the present study demonstrate that the invasive B. straminea snails seem to be incompatible with S. mansoni, suggesting a low risk of S. mansoni transmission in mainland China.

[Integration and demonstration of key techniques in surveillance and forecast of schistosomiasis in Jiangsu Province III Development of a machine simultaneously integrating mechanized environmental cleaning and automatic mollusciciding].

OBJECTIVE: To develop a machine simultaneously integrating mechanized environmental cleaning and automatic mollusciciding and to evaluate its effectiveness of field application, so as to provide a novel Oncomelania hupensis snail control technique in the large-scale marshlands. METHODS: The machine simultaneously integrating mechanized environmental cleaning and automatic mollusciciding, which was suitable for use in complex marshland areas, was developed according to the mechanization and automation principles, and was used for O. hupensis snail control in the marshland. The effect of the machine on environmental cleaning and plough was evaluated, and the distribution of living snails was observed at various soil layers following plough. The snail control effects of plough alone and plough followed by mollusciciding were compared. RESULTS: The machine could simultaneously complete the procedures of getting vegetation down and cut vegetation into pieces, plough and snail control by spraying niclosamide. After plough, the constituent ratios of living snails were 36.31%, 25.60%, 22.62% and 15.48% in the soil layers at depths of 0-5, 6-10, 11-15 cm and 16-20 cm respectively, and 61.91% living snails were found in the 0-10 cm soil layers. Seven and fifteen days after the experiment, the mortality rates of snails were 9.38% and 8.29% in the plough alone group, and 63.04% and 80.70% in the plough + mollusciciding group respectively (χ²7 d = 42.74, χ²15 d = 155.56, both P values < 0.01). Thirty days after the experiment, the densities of snails were 3.02 snails/0.1 m² and 0.53 snails/ 0.1 m² in the soil surface of the plough alone group and the plough + mollusciciding group, which decreased by 64.92% and 93.60%, respectively, and the decrease rate of snail density was approximately 30% higher in the plough + mollusciciding group than that in the plough alone group. CONCLUSIONS: The machine simultaneously integrating mechanized environmental cleaning and automatic mollusciciding achieves the integration of mechanical environmental cleaning and automatic niclosamide spraying in the complex marshland areas, which provides a novel technique of field snail control in the large-scale setting in China.

[Integration and demonstration of key techniques in surveillance and forecast of schistosomiasis in Jiangsu Province I Layout and effect of the demonstration sites for schistosomiasis surveillance and forecast].

OBJECTIVE: To explore and integrate the key techniques used in the surveillance and forecast of schistosomiasis in the water regions along the Yangtze River, so as to provide technical support for identifying rapidly the risk of schistosomiasis transmission and implementing control measures targeting the risk. METHODS: According to the distribution of water systems and water regions along the Yangtze River in Jiangsu Province, the demonstration sites for surveillance and forecast of schistosomiasis were set across the province, where the integration and demonstration of the techniques regarding monitoring of Schistosoma japonicum infection in sentinel mice, human and animal activities, release of forecast information, and emergency treatment of water regions at risk of infection were performed. The pattern of human and animal activities was compared with the S. japonicum infection in sentinel mice in the demonstration sites, and the operability of the release of information and emergency treatment of the risk of S. japonicum infection was evaluated. RESULTS: A total of 50 demonstration sites for surveillance and forecast of schistosomiasis were set in fixed anchor points, opening of the navigation lock to the Yangtze River, freight terminal, agritainment places, ferry, large construction places, and places for guaranteeing the Youth Olympic Games in 23 counties (districts) of 5 cities, Jiangsu Province. During the period between May. and September, 2014, the infectivity of water body was monitored by using 5 batches of sentinel mice, with a 99.06% (4,954/5,001) gross recovery rate of mice. S. japonicum infection was detected in a demonstration site, and an infected mouse was found, with a 0.02% (1/4,933) gross positive rate of sentinel mice. The field survey showed 2 088 person-times contacting water, including 91.95% (1,920/2,088) contacting water due to the production such as capturing fish, harvesting and cultivating crops, and repairing and building boats, and 8.05% (168/2 088) contacting water due to the life activity, such as fishing, washing vegetables and playing with water. The people contacted water predominantly in August and September (49.57%). A total of 859 boats containing 1,877 boatmen were observed, 68.22% (586/859) of which were fishing boats containing 1,306 fishermen (69.58%). There were 32 sheep found in 4 demonstration sites, and 3 sheep were seen in the demonstration site with infected sentinel mouse. Four blue forecasts (emergence of water contact) and one orange forecast (S. japonicum-infected sentinel mouse detected) were released across the province, with one forecast map released which showed 5 sites with fishing and one site with sheep grazing, one emergency response system initiated, mollusciciding implemented in 10 hm2 high-risk regions, 120 sheep grazed in fence, and 35 fishermen given health-education materials, schistosomiasis examination and preventive therapy. In addition, no acute schistosomiasis occurred in the demonstration site with S. japonicum-infected sentinel mice. CONCLUSIONS: The integration and demonstration of the techniques regarding monitoring of S. japonicum infection in sentinel mice, human and animal activities, release of forecast information, and emergency treatment of water regions at risk of infection provides an effective approach for the large-scale surveillance and forecast of schistosomiasis.

[Appropriate technology: a driver to eliminate schistosomiasis in China. In- sights gained from the First Forum on Schistosomiasis Control in China].

This paper described the First Forum on Schistosomiasis Control in China. With "Appropriate technology is essential to schistosomiasis prevention and control" as the topic, the forum shared the main interventions and experiences for schistosomiasis control and elimination, exhibited the recent achievements gained from the development of appropriate technology for schistosomiasis control, showed the technical support of appropriate technology for schistosomiasis elimination, and proposed the priority for the future research and development of appropriate technology for schistosomiasis control and elimination in China. It is considered that the forum builds a bridge for communicating information between the administrative sectors and specialized prevention and control institutions, between research institutions and manufactures, and between experts/professors and grassroots professional staff, and provides a platform to communicate the national schistosomiasis control knowledge of China.

[Integration and demonstration of key techniques in the surveillance and forecast of schistosomiasis in Jiangsu Province II Molluscicidal effect of 5% niclosamide ethanolamine granules in large-scale settings].

OBJECTIVE: To evaluate the field molluscicidal effect of 5% niclosamide ethanolamine granules, so as to provide a novel Oncomelania hupensis snail control approach for emergency treatment of high-risk settings. METHODS: Snail control tests with spraying of 5% niclosamide ethanolamine granules were conducted in two settings of 2 counties, and the dose-, time- and setting-specific field molluscicidal effects were tested. RESULTS: In the small-scale setting, spraying of 5% niclosamide ethanolamine granules at doses of 30, 40 and 50 g/m2 resulted in 54.55%, 68.41% and 73.45% 1-day snail mortality, 57.27%, 68.59% and 80.28% 3-day snail mortality, and 63.49%, 77.58% and 85.55% 7-day snail mortality, respectively, and no significant differences were detected in 1- and 3-day snail mortality caused by spraying of 5% niclosamide ethanolamine granules at doses of 30 and 40 g/m2 (all P > 0.05), while significant difference was found in the 7-day snail mortality (χ2 = 4.549, P < 0.05). In addition, spraying of 5% niclosamide ethanolamine granules at doses of 40 and 50 g/m2 resulted in comparable 1-, 3- and 7-day snail mortality (all P > 0.05). In the large-scale setting, spraying of 5% niclosamide ethanolamine granules at a dose of 40 g/m2 resulted in 85.29% and 87.70% 3-day snail mortality, 83.89% and 91.02% 7-day snail mortality, and 83.41% and 91.84% 15-day snail mortality in the environment-cleaning group and non-cleaning group, respectively. The overall snail mortality was 90.02% in the environment-cleaning group 3 to 15 days after spraying, which was significantly higher than that (84.28%) in the non-cleaning group (χ2 = 9.950, P < 0.05). After 15 days of spraying with 5% niclosamide ethanolamine granules at a dose of 40 g/m2, the densities of living snails reduced from 19.90 and 19.83 snails/0.1 m2 to 0.60 and 2.60 snails/0.1 m2 in the environment-cleaning group and non-cleaning group, with 96.98% and 86.89% reductions, respectively. CONCLUSION: The appropriate dose of 5% niclosamide ethanolamine granules is 40 g/m2 for snail control in the field, and environment cleaning of vegetation with a height of more than 50 cm may improve the molluscicidal efficacy.

[Evaluation on molluscicidal effect of chlorosalicylicamide on Oncomelania hupensis in schistosomiaisis endemic areas of eight provinces in China].

OBJECTIVE: To evaluate the effects of a novel molluscicide, the salt quinoid-2', 5-dichloro-4'-nitrosalicylanilide from niclosamide (LDS), with 10% wettable powder, in main schistosomiasis epidemic areas of China, including Hunan, Jiangxi, Hubei, Anhui, Jiangsu, Sichuan, Yunnan and Zhejiang Province. METHODS: In the immersion test, 6 effective concentrations of 10% LDS were tested respectively: 0.1, 0.2, 0.4, 0.6, 0.8, 1.0 g/m3 in the field; at the same time, 50% wettable powder of niclosamide ethanolamine salt (WPN) with effective concentrations of 1.0 g/m was used as the molluscicide control, and the fresh water as the blank control, then the mortality rates of 0. hupensis snails were recorded at 24 h, 48 h and 72 h after the immersion. In the spraying test and powder-spraying test, 5 effective dosages of 10% LDS were tested respectively: 0.2, 0.4, 0.6, 0.8, 1.0 g/m2, while 50% WPN 1.0 g/m2 was used as the molluscicide control, and the fresh water as the blank control in the field for 1 d, 3 d and 7 d, then the mortality rates of O. hupensis snails were recorded at 1 d, 3 d and 7 d after the spraying and powder-spraying. RESULTS: The snail mortality rates of LDS using the immersion test for 72 h were more than 95% in the field of eight provinces (0.1 g/m in Sichuan, Jiangxi, Jiangsu and Zhejiang provinces, 0.2 g/m3 in Yunnan, Hunan and Hubei provinces, and 0.4 g/min Anhui Province); the snail mortality rates of LDS using the spraying test for 7 d were more than 85% (0.2 g/m2 in Hunan, Hubei, Jiangxi and Zhejiang provinces, 0.4 g/m2 in Sichuan and Anhui provinces, 0.6 g/m2 in Yunnan and Jiangsu provinces). The snail mortality rates of LDS the powder-spraying test for 7 d were more than 85% (0.6 g/m2 in Yunnan, Sichuan, Hubei, Jiangxi, Anhui, Jiangsu and Zhejiang provinces). According to the standards of "Efficacy test methods and evaluation of molluscicide for pesticide registration (NY/T 1617-2008)", LDS is a qualified molluscicide. CONCLUSIONS: LDS has good molluscicidal effects through the immersion, spraying and powder-spraying test in the fields. It is suitable for a variety of environments to control O. hupensis snails of schistosomiasis endemic areas in China. The recommended dosages of LDS are 0.1-0.2 g/m3 by the immersion method, 0.2-0.4 g/m2 by the spraying method, and 0.4-0.6 g/m2 by the powder-spraying method in the fields.

Resistance to niclosamide in Oncomelania hupensis, the intermediate host of Schistosoma japonicum: should we be worried?

As the currently only available molluscicide, niclosamide has been widely used for snail control for over 2 decades in China. There is therefore a concern about the emergence of niclosamide-resistant snail populations following repeated, extensive use of the chemical. The purpose of this study was to investigate the likelihood of niclosamide resistance in Oncomelania hupensis in China. Active adult O. hupensis snails derived from 20 counties of 10 schistosomiasis-endemic provinces of China, of 10 snails in each drug concentration, were immersed in solutions of 1, 0.5, 0.25, 0.125, 0.063, 0.032, 0.016 and 0.008 mg L-1 of a 50% wettable powder of niclosamide ethanolamine salt (WPN) for 24 and 48 h at 25 °C, and the median lethal concentration (LC50) was estimated. Then, the 24- and 48-h WPN LC50 values were compared with those determined in the same sampling sites in 2002. The results indicated that the 24- and 48-h WPN LC50 values for O. hupensis were not significantly different from those determined in 2002 (P = 0.202 and 0.796, respectively). It is concluded that the current sensitivity of O. hupensis to niclosamide has not changed after more than 2 decades of repeated, extensive application in the main endemic foci of China, and there is no evidence of resistance to niclosamide detected in O. hupensis.

[Clinical manifestations and treatment of schistosomiasis hematobia].

Schistosomiasis hematobia is one major human schistosomiasis. The disease is endemic in Africa and Mediterra- nean region, and is the main cause of urogenital diseases. Although only Schistosoma japonicum is spreading across the Mainland China, now more schistosomiasis hematobia cases are reported among aid projects and migrant workers to Africa, with the economy development and the increasing degree of foreign exchanges. Meanwhile, the relevant clinical data of.schistosomiasis hematobia are rare in China. This article reviews the clinical manifestations and progress in diagnosis and treatment of the disease.

Apropos: factors impacting on progress towards elimination of transmission of schistosomiasis japonica in China.

Currently, China is moving towards the elimination of schistosomiasis japonica. In a previous review, the factors affecting the progress towards the elimination of transmission of schistosomiasis in China have been summarized. Nevertheless, some factors were neglected. Hereby, we describe four other factors which may threaten the achievement of the goal of schistosomiasis elimination in China.