Schistosomiasis Endemic Areas Research Articles

Effect of Maternal Schistosoma mansoni Infection and Praziquantel Treatment During Pregnancy on Schistosoma mansoni Infection and Immune Responsiveness among Offspring at Age Five Years

IntroductionOffspring of Schistosoma mansoni-infected women in schistosomiasis-endemic areas may be sensitised in-utero. This may influence their immune responsiveness to schistosome infection and schistosomiasis-associated morbidity. Effects of praziquantel treatment of S. mansoni during pregnancy on risk of S. mansoni infection among offspring, and on their immune responsiveness when they become exposed to S. mansoni, are unknown. Here we examined effects of praziquantel treatment of S. mansoni during pregnancy on prevalence of S. mansoni and immune responsiveness among offspring at age five years.MethodsIn a trial in Uganda (ISRCTN32849447, http://www.controlled-trials.com/ISRCTN32849447/elliott), offspring of women treated with praziquantel or placebo during pregnancy were examined for S. mansoni infection and for cytokine and antibody responses to SWA and SEA, as well as for T cell expression of FoxP3, at age five years.ResultsOf the 1343 children examined, 32 (2.4%) had S. mansoni infection at age five years based on a single stool sample. Infection prevalence did not differ between children of treated or untreated mothers. Cytokine (IFNγ, IL-5, IL-10 and IL-13) and antibody (IgG1, Ig4 and IgE) responses to SWA and SEA, and FoxP3 expression, were higher among infected than uninfected children. Praziquantel treatment of S. mansoni during pregnancy had no effect on immune responses, with the exception of IL-10 responses to SWA, which was higher in offspring of women that received praziquantel during pregnancy than those who did not.ConclusionWe found no evidence that maternal S. mansoni infection and its treatment during pregnancy influence prevalence and intensity of S. mansoni infection or effector immune response to S. mansoni infection among offspring at age five years, but the observed effects on IL-10 responses to SWA suggest that maternal S. mansoni and its treatment during pregnancy may affect immunoregulatory responsiveness in childhood schistosomiasis. This might have implications for pathogenesis of the disease.

Radical cystectomy is the treatment of choice for invasive bladder cancer.

Bladder cancer is the second most common urologic cancer and the sixth most common overall cancer in Canada, accounting for 6700 new cases per year. It has the fourth highest incidence among cancers in men and the twelfth in females. It represents up to 5.8% of new cancer cases and 3.3% of deaths in Canadian men.1 Tobacco smoking is the most established risk factor, leading to 50% to 65% and 20% to 30% of male and female cases, respectively.2 Other risk factors include occupational exposure to benzene derivatives and aryl amines, phenacetin abuse, external beam radiation therapy, dietary factors, cyclophosphamide and chronic urinary tract infections (especially with schistosomiasis in endemic areas).3–8

S. haematobium as a Common Cause of Genital Morbidity in Girls: A Cross-sectional Study of Children in South Africa

Background Schistosoma (S.) haematobium infection is a common cause of genital morbidity in adult women. Ova in the genital mucosal lining may cause lesions, bleeding, pain, discharge, and the damaged surfaces may pose a risk for HIV. In a heterogeneous schistosomiasis endemic area in South Africa, we sought to investigate if young girls had genital symptoms and if this was associated with urinary S. haematobium.MethodologyIn a cross-sectional study of 18 randomly chosen primary schools, we included 1057 schoolgirls between the age of 10 and 12 years. We interviewed assenting girls, whose parents had consented to their participation and examined three urines from each of them for schistosome ova.Principal findingsOne third of the girls reported to have a history of genital symptoms. Prior schistosomal infection was reported by 22% (226/1020), this was associated with current genital symptoms (p<0.001). In regression analysis the genital symptoms were significantly associated both with urinary schistosomiasis (p<0.001) and water contact (p<0.001).ConclusionsEven before sexually active age, a relatively large proportion of the participating girls had similar genital symptoms to those reported for adult genital schistosomiasis previously. Anti-schistosomal treatment should be considered at a young age in order to prevent chronic genital damage and secondary infections such as HIV, sexually transmitted diseases and other super-infections.

The new national integrated strategy emphasizing infection sources control for schistosomiasis control in China has made remarkable achievements

Schistosomiasis japonica remains one important public health concern that cause great loss of humans' health and social-economic development in the Peoples' Republic of China. At the end of 1990s and the beginning of 2000s, there were still about 0.8 million patients and nearly 85 million people living in the epidemic areas around China. We undertook full analysis of the epidemiological data of schistosomiasis taken from the report of schistosomiasis status in People's Republic of China from 1999 to 2010 for effectiveness assessment of China's new strategy for schistosomiasis control nationwide after its implementation since the beginning the 21st century. The schistosomiasis-endemic uncontrolled counties or towns decreased in number from 1,149 in 2002 to 643 in 2010 at a rate of 44%. The number of schistosomiasis patients decreased from nearly 800,000 to less than 326,000 in 2010 at a decrease rate of more than 50%. The number of acute schistosomiasis patients also decreased significantly, and only 43 cases were reported in 2010. The infection rates of cattle in the endemic uncontrolled provinces decreased greatly though the number of cattle and the actual snail habitat areas remained large with no obvious decline. The schistosome infection rates of human and cattle both decreased significantly by more than 64% and 75%. However, most of the uncontrolled schistosomiasis-endemic areas, schistosomiasis patients, and acute cases are generally located in the four provinces (Hunan, Hubei, Jiangxi, and Anhui) of the lake regions in the middle and lower reach of the Yangtze River, and the egg-positive rates in diagnosed human in endemic Hunan and Hubei remained higher than 10%. Therefore, the new strategy of schistosomiasis control via integrated measures emphasizing infection source control is scientific and successful around China, though it is essential to explore an effective and sustainable strategy for schistosomiasis control in the tough lake and marshland regions of China. The four provinces (Hunan, Hubei, Jiangxi, and Anhui) of the lake regions in China are the main battlefield of China's schistosomiasis control in the present and future.

Genital Schistosomiasis Leading to Ectopic Pregnancy and Subfertility: A Case for Parasitic Evaluation of Gynaecologic Patients in Schistosomiasis Endemic Areas

Female genital schistosomiasis is a significant risk factor for ectopic pregnancy and infertility in schistosomiasis-endemic areas. A case of one previous ectopic pregnancy and subsequent obstruction of the contralateral tube in a secondary subfertility patient with chronic genital schistosomiasis is presented, emphasizing the need for a detailed history and parasitic evaluation of patients presenting with ectopic pregnancy or subfertility in areas where the disease is endemic.

Evaluation of Loop-Mediated Isothermal Amplification Suitable for Molecular Monitoring of Schistosome-Infected Snails in Field Laboratories

We previously described loop-mediated isothermal amplification (LAMP) for detection of Schistosoma haematobium and S. mansoni DNA in infected snails. In the present study, we adapted the LAMP assay for application in field laboratories in schistosomiasis-endemic areas. Isolation of DNA was simplified by blotting snail tissue (extracted in NaOH/sodium dodecyl sulfate) onto treated membranes, which enabled preservation at ambient temperatures. A ready-mix of LAMP reagents, suitable for shipment at ambient temperature and storage in minimal refrigeration, was used. Local survey teams without experience in molecular biology acquired operational expertise with this test within a few hours. Fifty-four field-caught snails were tested locally by LAMP and 59 were tested at similar conditions in Jerusalem. The LAMP results were consistent with those of a polymerase chain reaction; only four samples showed false-negative results. Results indicate that LAMP assays are suitable for detection of S. haematobium and S. mansoni in low-technology parasitology laboratories in which schistosomiasis elimination activities are undertaken.

Adult worm‐specific IgE/IgG4 balance is associated with low infection levels of Schistosoma mansoni in an endemic area

Field studies have suggested an immune-mediated mechanism associated with resistance to Schistosoma mansoni infection. Overall, levels of specific IgE have been correlated with resistance to infection, whereas levels of IgG4 have been associated with susceptibility. This study aimed to evaluate serum levels of soluble adult worm antigen preparation (SWAP)-specific IgE and IgG4 in relation to current infection in a large casuistic of individuals living in an endemic area of schistosomiasis in Bahia, Brazil. The prevalence of S.mansoni infection was 37·7% and the mean parasite burden was 55·4 (0-2100) epg/faeces. There was no significant difference in the levels of SWAP-specific IgE in individuals with different parasite burden, whereas high producers of parasite-specific IgG4 presented higher parasite burden when compared to low IgG4 producers. Additionally, S.mansoni parasite load was positively correlated with the levels of specific IgG4 or total IgE. No significant correlation was observed between parasite burden and SWAP-specific IgE. Nevertheless, SWAP-specific IgE/IgG4 ratio was higher in uninfected or lightly infected individuals (1-99 epg/faeces) than in heavily infected ones (≥400 epg/feces). These findings highlight the important role of IgE/IgG4 ratio in the resistance to infection, which could be useful for further studies in schistosomiasis vaccine candidates.

Urinary Schistosomiasis in Asylum Seekers in Italy: An Emergency Currently Undervalued

Despite schistosomiasis is one of the most prevalent tropical diseases in developing countries and and large flows of migrants come from countries where the disease is endemic, imported urinary schistosomiasis is still not easily recognized in non-endemic areas, especially if not subjected to specific investigations. Moreover schistosomiasis is currently not reportable in any European public health system. The data presented in this report were collected were collected between asylum seekers by a simple screening method based on a prior or actual history of a macroscopic hematauria. In case of a history of gross hematuria, the patient underwent to specific exams standardized for the diagnosis of urinary schistosomiasis. Our data show that the prevalence of the disease has been largely underestimated by European Surveillance Systems; in fact in a small population of young asylum seekers coming from endemic areas for schistosomiasis, we found a significant number of individuals with symptomatic disease. Given that the disease typically has an insidious course, it is highly probable that a screening procedure is able to identify early asymptomatic or mildly symptomatic subjects and avoid the serious complications that are present in advanced stages of disease. Given the limits and the costs of a late diagnosis and that an effective treatment is available, subjects from endemic areas should be actively screened for urinary schistosomiasis.

Modelling the ecological niche of hookworm in Brazil based on climate

The distribution of hookworm in schistosomiasis-endemic areas in Brazil was mapped based on climate suitability. Known biological requirements of hookworm were fitted to data in a monthly long-term normal climate grid (18 x 18 km) using geographical information systems. Hookworm risk models were produced using the growing degree day (GDD) water budget (WB) concept. A moisture-adjusted model (MA-GDD) was developed based on accumulation of monthly temperatures above a base temperature of 15 °C (below which there is no lifecycle progression of Necator americanus) conditional on concurrent monthly values (rain/potential, evapotranspiration) of over 0.4. A second model, designated the gradient index, was calculated based on the monthly accumulation of the product of GDD and monthly WB values (GDD x WB). Both parameters had a significant positive correlation to hookworm prevalence. In the northeastern part of Brazil (the Caatinga), low hookworm prevalence was due to low soil moisture content, while the low prevalence in southern Brazil was related to low mean monthly temperatures. Both environmental temperature and soil moisture content were found to be important parameters for predicting the prevalence of N. americanus.

A novel immunodiagnostic assay to detect serum antibody response against selected soluble egg antigen fractions from Schistosoma japonicum.

BackgroundSchistosomiasis japonica remains a real threat to public health in China. The currently used immunodiagnostic assays are sensitive and have a certain degree of specificity, however, they all use complex crude antigens, are based on detection of schistosome-specific antibodies, and have been shown to cross-react with other parasitic diseases. Therefore, these assays cannot be used to evaluate chemotherapy efficacy. The development of highly sensitive and highly specific immunodiagnostic techniques that can monitor the decline of antibodies specific for S. japonica will be extremely valuable as part of the ongoing strategy to control schistosomiasis in endemic areas. Here we report on the identification of unique fraction antigens of soluble egg antigen (SEA) to which the antibodies disappear 7 weeks after effective treatment. Furthermore, we use these SEA fractions to develop a modified assay with both high sensitivity and specificity.Methodology/Principal FindingsSEA of S. japonicum was fractionated by electrophoresis using 7.5% SDS-PAGE under non-reducing conditions. The SEA fraction antigens to which antibodies were decreased soon after treatment were collected and used as the detection antigens to establish the FA-ELISA. Sera from patients with acute and chronic schistosomiasis infection, healthy people, and those with other parasitic diseases, were used to evaluate their sensitivity and specificity. Furthermore, sera from patients with chronic schistosomiasis infection were evaluated before and after treatment at different time points to evaluate their chemotherapeutic efficacy.Conclusion/SignificanceWe demonstrated that this novel FA-ELISA provided high sensitivity and specificity, with very low cross-reactivity, and can serve as an effective tool to determine the efficacy of chemotherapy against S. japonicum.

Hallazgos radiológicos en pacientes con esquistosomiasis importada

IntroductionImaging techniques, primarily ultrasound, are useful in the diagnosis and monitoring of patients with schistosomiasis in endemic areas. MethodsStudy of 219 patients treated in sub-Saharan Tropical Medicine Unit with a diagnosis of imported schistosomiasis by imaging techniques investigations including plain abdominal radiography and ultrasound. ResultsA total of 17.8% of patients who had an abdominal X-ray showed findings suggestive of schistosomiasis, in most cases bladder calcifications. In 73 patients (41%) ultrasound showed pathological findings, mainly diffuse or focal wall thickening (26 patients), nodular lesions (n=14), and pseudopolyps (n=8). One patient, who had a large bladder mass (9cm) and bilateral ureterohydronephrosis, was finally diagnosed with squamous cell carcinoma of the bladder. Ultrasound liver abnormalities were found in 10 patients, 4 with signs of portal hypertension, of which 3 had the characteristic periportal fibrosis in schistosomiasis. ConclusionImaging studies, especially abdominal and bladder ultrasound, are useful for diagnosis, the study of disease and monitoring of patients with schistosomiasis in non-endemic countries.

Functional Polymorphisms in IL13 Are Protective against High Schistosoma mansoni Infection Intensity in a Brazilian Population

BackgroundIL-13 is a signature cytokine of the helper T cell type 2 (TH2) pathway which underlies host defense to helminthic infection and activates production of IgE in both parasitized populations and in urban settings after allergen exposure.Methodology/Principal FindingsTwo functional polymorphisms in IL13, rs1800925 (or c.1-1111C>T) and rs20541 (or R130Q) were previously found to be associated with Schistosoma hematobium infection intensity. They have not been thoroughly explored in S. mansoni-endemic populations, however, and were selected along with 5 tagging SNPs for genotyping in 812 individuals in 318 nuclear families from a schistosomiasis-endemic area of Conde, Bahia, in Brazil. Regression models using GEE to account for family membership and family-based quantitative transmission disequilibrium tests (QTDT) were used to evaluate associations with total serum IgE (tIgE) levels and S. mansoni fecal egg counts adjusted for non-genetic covariates. We identified a protective effect for the T allele at rs20541 (P = 0.005) against high S. mansoni egg counts, corroborated by QTDT (P = 0.014). Our findings also suggested evidence for protective effects for the T allele at rs1800925 and A allele at rs2066960 after GEE analysis only (P = 0.050, 0.0002).Conclusions/SignificanceThe two functional variants in IL13 are protective against high S. mansoni egg counts. These markers showed no evidence of association with tIgE levels, unlike tIgE levels previously studied in non-parasitized or atopic study populations.

The Effect of Antihelminthic Treatment on Subjects with Asthma from an Endemic Area of Schistosomiasis: A Randomized, Double-Blinded, and Placebo-Controlled Trial

This is a prospective, double-blinded, and placebo-controlled trial evaluating the influence of antihelminthic treatments on asthma severity in individuals living in an endemic area of schistosomiasis. Patients from group 1 received placebo of Albendazole or of Praziquantel and from group 2 received Albendazole and Praziquantel. Asthma severity was assessed by clinical scores and by pulmonary function test. There was no significant difference in the asthma scores from D0 to D1–D7 after Albendazole or Praziquantel and from D0 to D30–90 after Albendazole or Praziquantel in both, group 1 and 2. It was observed, however, a clinical worsening of the overall studied population after 6 months and 12 months of antihelminthic treatments. Additionally, we observed increased frequency of forced expiratory volume in 1 second (FEV1) <80% on 12 and 18 months after treatment. The worsening of asthma severity after repeated antihelminthic treatments is consistent with the hypothesis of the protective role conferred by helminths in atopic diseases.

Intestinal Schistosomiasis as Unusual Aetiology for Acute Appendicitis, Nowadays a Rising Disease in Western Countries

Intestinal schistosomiasis as unusual aetiology for acute appendicitis, nowadays a rising disease in western countries. Recent changes in global migration has led to an immigration growth in our scenario, upsurging people coming from endemic areas of schistosomiasis. Schistosomal appendicitis, seldom reported in developed countries, is now an expected incrising entity in our hospitals during the near future. Due to this circumstances, we believe that schistosomiasis should be consider as a rising source for acute appendicitis in western countries. In order to illustrate this point, we present a case of a 45-years-old black man, from Africa, was admitted via A&E because of acute abdominal pain, located in right lower quadrant. Acute appendicitis was suspected, and he underwent laparotomy and appendectomy. Pathological study by microscope revealed a gangrenous appendix with abscesses and parasitic ova into the submucosal layer of the appendix, suggesting Schistosomiasis.

Schistosomiasis transmission and environmental change: a spatio-temporal analysis in Porto de Galinhas, Pernambuco--Brazil.

BackgroundIn Brazil, schistosomiasis mansoni infection is an endemic disease that mainly affects the country’s rural populations who carry out domestic and social activities in rivers and water accumulations that provide shelter for the snails of the disease. The process of rural migration to urban centers and the disorderly occupation of natural environments by these populations from endemic areas have favored expansion of schistosomiasis to locations that had been considered to be disease-free. Based on environmental changes that have occurred in consequent to an occupation and urbanization process in the locality of Porto de Galinhas, the present study sought to identify the relationship between those chances, measure by remote-sensing techniques, and establish a new endemic area for schistosomiasis on the coast of Pernambuco State - Brazil.MethodsTo gather prevalence data, two parasitological census surveys were conducted (2000 and 2010) using the Kato-Katz technique. Two malacological surveys were also conducted in the same years in order to define the density and infection rate of the intermediate host. Based on these data, spatial analyses were done, resulting in maps of the risk of disease transmission. To ascertain the environmental changes that have occurred at the locality, images from the QuickBird satellite were analyzed, thus resulting in land use maps.ResultsOver this 10-year period, the foci of schistosomiasis became more concentrated in the Salinas district. This area was considered to be at the greatest risk of schistosomiasis transmission and had the highest prevalence rates over this period. The study illustrated that this was the area most affected by the environmental changes resulting from the disorderly urbanization process, which gave rise to unsanitary environments that favored the establishment and maintenance of foci of schistosomiasis transmission, thereby consolidating the process of expansion and endemization of this parasitosis.

Risk Factors for Asthma in a Helminth Endemic Area in Bahia, Brazil

Protective factors associated with atopy or asthma in rural areas include socioeconomic level, overcrowding, and helminth infection. However, little epidemiological information was originated from schistosomiasis areas. This study aimed to investigate factors associated with asthma in a schistosomiasis endemic area. A questionnaire was used to obtain information on demographics, socioeconomic, and environmental features. The ISAAC questionnaire was used to identify individuals with asthma. Parasitological exam was done in all participants and skin prick test to aeroallergens in all asthmatics. Prevalence of Schistosoma mansoni infection was 57.4% and Ascaris lumbricoides, 30.8%. Asthma was found in 13.1% of the population, and 35.1% of them had a positive SPT. Active and passive smoking was positively associated with asthma, whereas A. lumbricoides was negatively associated. In a schistosomiasis hyperendemic region, current infection with A. lumbricoides is protective against asthma. However, we cannot rule out the involvement of S. mansoni infection in this process.

Effect of a combination of the new antischistosomal drug Ro 15-5458 and praziquantel on different strains of Schistosoma mansoni infected mice.

The possible additive or synergistic effects of both praziquantel (CAS 55268-74-1) and a new antischistosomal drug, Ro 15-5458 (10-(2-diethylamino)thyl)-9-acridanone(thiazolidin-2-yl-i dene)hydrazone, CAS 92928-47-7) were studied in two different strains of Schistosoma mansoni infected mice, namely CD susceptible and SO4 resistant strains. Assessment of cure was performed using the following parameters: hepatic and intestinal tissue egg load and distribution, oogram changes in the small intestine and histopathological examination of the mice livers. In this study, a combination was used between 1/3 the curative doses of praziquantel and Ro 15-5458. This combination therapy proved to be beneficial as regards the percentage parasite reduction and hepatic worm shift (99.4% and 100%, respectively, in the CD susceptible mouse strains, compared to 84.1% and 34.8% in the SO4 resistant strains). Treatment with subcurative doses of praziquantel and Ro 15-5458 resulted in 78.6% intestinal dead ova and 21.4% mature ones. This score shifted to 98.6% and 1.4% dead and mature ova, respectively, in the SO4 resistant strains. Again the range of liver granulomata in the CD susceptible and SO4 resistant strains receiving subcurative doses of both drugs was 4-6 and 2-5, respectively, in five successive low power fields, while in the infected untreated control mice, this range reached 8-11 and 5-9, respectively. Histopathological sections of the liver revealed a small fibrocellular granuloma with few inflammatory cells and excess fibrous collagen tissue deposition in animals undergoing the combination therapy. This contrasts with the large fibrocellular granulomata seen in the infected untreated control mice. These results may be of value in endemic areas of schistosomiasis, due to the unexpected emergence of drug resistance against the currently used antischistosomal drug, praziquantel in these areas.

Evaluation of an IgY-Based Immunomagnetic Enzyme-Linked Immunosorbent Assay System for Detection of Circulating Schistosoma japonicum Antigen in Serum Samples from Patients in China

We have developed a novel egg yolk antibody (IgY)-coated magnetic beads antigen-capture immunoassay for detection of a circulating antigen of Schistosoma japonicum in serum samples of patients in schistosomiasis-endemic areas of China. This IgY-based immunomagnetic bead enzyme-linked immunosorbent assay (IgY-IMB-ELISA) uses polyclonal IgY-coated magnetic beads as a capture antibody, and a monoclonal IgG as a detection antibody. The sensitivity of the magnetic immunoassay was 100% (40 of 40) in cases of acute infection and 91.5% (107 of 117) in chronic cases of schistosomiasis, and no positive reaction was found in 0 of 49 healthy persons. Cross-reactivity was 3.3% (1 of 33) with clonorchiasis and 0% (0 of 20) with paragonimiasis. There was a significant correlation between ELISA absorbance value and egg count (eggs per gram feces) and a correlation coefficient of 0.88 in a small sample of 14 patients. The results demonstrated that the IgY-IMB-ELISA is a sensitive and specific assay for detection of human schistosomiasis japonica.

Magnetic resonance of the liver in acute schistosomiasis

A 15-year-old boy developed persistent fever and a diffuse maculopapular rash 21 days before admission to hospital. He was treated with antibiotics and symptomatic drugs without improvement. Clinical examination revealed a well developed underweight teenager, with pale skin. His axillary temperature was 39.3oC. There was no history of diarrhea. Abdominal palpation showed painful hepatomegaly and splenomegaly. Leukocytosis (38,000 cels/mL) and eosinophilia (30,400 cels/mL) was found in a routine blood count. Platelet counts and hemoglobin levels were within the normal range and serum alanine aminotransferase was slightly elevated. Abdominal ultrasound showed liver and spleen enlargement and periportal lymph nodes. Schistosoma mansoni eggs were described in the stools. He reported contact with stream water in an endemic area for schistosomiasis 30 days before the start of symptoms. Magnetic resonance of the liver disclosed disseminated hypointense nodules (Figure A: T1 weighted imaging after intravenous gadolinium injection – black arrows) and periportal lymph nodes (Figure B: a T2 weighted imaging with a periportal lymph node – white arrow). These findings suggest the presence of huge granulomas of the acute phase of schistosomiasis mansoni in the liver. To our knowledge, this is the first description of MR of the liver in acute schistosomiasis.

Evaluation of a New Molluscicide for Counteracting the Intermediate Snail Host ofSchistosoma japonicum

A novel molluscicide, derived from niclosamide, the salt of quinoid-2′,5-dichloro-4′-nitrosalicylanilide (LDS) was recently developed in China. The molluscicidal activity of LDS was compared with the commonly used molluscicide niclosamide (WPN) by immersion at seven concentrations; 0.05, 0.1, 0.2, 0.4, 0.8, 1.6, and 3.2 mg/L, and with spraying and powdering methods (dosages of 0.2, 0.4, and 0.8 g/m2) in the laboratory and the field. We recorded mortality at 1 d, 3 d, and 7 d. The results showed that at 0.4 mg/L immersion exposure for 72 hours, snail mortalities for LDS and WPN were 100% and 96.70% respectively in the lab, and 100% and 95.33 ± 1.15% respectively in the field. With a dosage of 0.8 g/m2 exposure for 7 d by spraying, snail mortalities for LDS and WPN were 100% and 97.33 ± 2.30% respectively in the lab, and 99.27 ± 1.27% and 97.47 ± 3.11 % in the field. With a dosage of 0.8 g/m2 exposure at 7 d by powdering, snail mortalities for LDS and WPN were both 98% in the lab, and 100% in the field. These results from three different methods show that molluscicidal effects were similar in the lab and the field. However, LDS is much cheaper than WPN, and LDS is less toxic to fish than WPN. Therefore, LDS might be more useful than WPN for controlling snails in endemic areas of schistosomiasis in China.