Assessment of morbidity in Schistosoma haematobium infection: current methods and future tools

Urinary interleukins (IL)-6 and IL-10 in schoolchildren from an area with low prevalence of Schistosoma haematobium infections in coastal Kenya

Urinary cytokines are gaining traction as tools for assessing morbidity in infectious and non-infectious inflammatory diseases of the urogenital tract. However, little is known about the potential of these cytokines in assessing morbidity due to S. haematobium infections. Factors that may influence the urinary cytokine levels as morbidity markers also remain unknown. Therefore the objective of the present study was to assess how urinary interleukins (IL-) 6 and 10 are associated with gender, age, S. haematobium infections, haematuria and urinary tract pathology and; 2) to assess the effects of urine storage temperatures on the cytokines. This was a cross-sectional study in 2018 involving 245 children aged 5-12 years from a S. haematobium endemic area of coastal Kenya. The children were examined for S. haematobium infections, urinary tract morbidity, haematuria and urinary cytokines (IL-6 and IL-10). Urine specimens were also stored at -20°C, 4°C or 25°C for 14 days before being assayed for IL6 and IL-10 using ELISA. The overall prevalence of S. haematobium infections, urinary tract pathology, haematuria, urinary IL-6 and urinary IL-10 were 36.3%, 35.8%, 14.8%, 59.4% and 80.5%, respectively. There were significant associations between prevalence of urinary IL-6, but not IL-10, and age, S. haematobium infection and haematuria (p = 0.045, 0.011 and 0.005, respectively) but not sex or ultrasound-detectable pathology. There were significant differences in IL-6 and IL-10 levels between urine specimens stored at -20°C and those stored at 4°C (p<0.001) and, between those stored at 4°C and those stored at 25°C (p<0.001). Urinary IL-6, but not IL-10, was associated with children's age, S. haematobium infections and haematuria. However, both urinary IL-6 and IL-10 were not associated with urinary tract morbidity. Both IL-6 and IL-10 were sensitive to urine storage temperatures.

Assessment of fecal calprotectin and fecal occult blood as point-of-care markers for soil-transmitted helminth attributable intestinal morbidity in a case-control substudy conducted in Côte d'Ivoire, Lao PDR and Pemba Island, Tanzania

BACKGROUND

Infections with soil-transmitted helminths (STHs) may result in chronic inflammatory disorders affecting the human host. The objective of this study was to evaluate Fecal Calprotectin (FC) and Fecal Occult Blood (FOB) in individuals infected and non-infected with STHs to identify potential intestinal morbidity markers.

METHODS

Stool from participants diagnosed positive for Trichuris trichiura and concomitant STH infections from three countries was used to perform FC and FOB point-of-care assays. Simultaneously, identified STH negative participants underwent FC and FOB testing as controls. Potential associations between test results and determinants were analyzed using multivariable logistic regression.

FINDINGS

In total, 1034 T. trichiura infected cases (mostly light infections) and 157 STH negative controls were tested for FC and FOB. Among all participants tested, 18·5% had ≥ 50 µg/g FC concentration, while 14 (1·2%) were positive for FOB. No statistically significant association was found between T. trichiura infection or Ascaris lumbricoides co-infection and FC concentration, while an inverse association (odds ratio (OR): 0·45, 95% credible intervals (CrI): 0·26, 0·75) was found between hookworm co-infection and FC concentration. In Lao PDR, the proportion of participants in the ≥ 50 µg/g FC category was significantly higher in the oldest age category compared to the 5-11 years group (OR: 3·31, 95% CrI: 1·62, 7·24). Too few participants were found positive for FOB to derive any conclusions.

INTERPRETATION

Studies are needed to better understand the relationship between intestinal morbidity and STH infections. Suitable, standardized, low-cost markers of STH attributable morbidity to better monitor the impact of STH control interventions are necessary.

FUNDING

BMGF (OPP1153928).

Elevation of C-reactive protein, P-selectin and Resistin as potential inflammatory biomarkers of urogenital Schistosomiasis exposure in preschool children

Background

Schistosomiasis is known to induce inflammatory immune responses. C-reactive protein (CRP), resistin and P-selectin are serological inflammatory markers that rise during the acute stages of infection. Here, we propose such inflammatory biomarkers have a potential for use in urogenital schistosomiasis diagnostic screening for exposure and infection in preschool-aged children.

Methods

As part of a larger study on urogenital schistosomiasis, 299 preschool children aged 1–5 years were included in this cross-sectional study. Parasitological diagnosis was conducted using urine filtration for Schistosoma haemtobium infection, and Kato Katz for S. mansoni infection. Serum levels of P-selectin, resistin, CRP, and antibodies against S. haematobium cercarial antigen preparation (CAP) and soluble worm antigen preparation (SWAP) were measured by ELISA.

Results

Of the 299 participants, 14% were egg positive for S. haematobium. Serology showed 46 and 9% of the participants to have been exposed to S. haematobium cercarial antigens and adult worm antigens, respectively. Levels of P-selectin were significantly higher in participants infected with S. haematobium (egg-positive) than in uninfected participants (p = 0.001). Levels of P-selectin were also higher in those exposed to cercarial antigen than in unexposed participants (p = 0.019). There was a positive correlation between P-selectin and infection intensity (r = 0.172; p = 0.002), as well as with IgM responses to CAP and SWAP (r = 0.183; p = 0.001); (r = 0.333; p < 0.0001) respectively. CRP significantly correlated with IgM responses to CAP (r = 0.133; p = 0.029) while resistin correlated with IgM responses to CAP and SWAP (r = 0.127; p = 0.016); (r = 0.197; p = 0.0004). CRP levels were higher in those exposed to cercarial and adult worm antigens than unexposed participants (p = 0.035); (p = 0.002) respectively, while resistin was higher in participants exposed to cercarial antigen than unexposed participants (p = 0.024).

Conclusion

In this preschool population, P-selectin is significantly associated with urogenital schistosome infection and intensity; hence a potential biomarker for infection diagnosis and disease monitoring. The inflammatory biomarkers (P-selectin, Resistin and CRP) were significantly higher in participants exposed to cercarial antigens than unexposed individuals indicating an underlying inflammatory environment.

Schistosoma haematobium and soil-transmitted Helminths in Tana Delta District of Kenya: infection and morbidity patterns in primary schoolchildren from two isolated villages

BACKGROUND

Schistosomes and soil-transmitted helminths (STH) (hookworm, Trichuris trichiura and Ascaris lumbricoides) are widely distributed in developing countries where they infect over 230 million and 1.5 billion people, respectively. The parasites are frequently co-endemic and many individuals are co-infected with two or more of the species, but information on how the parasites interact in co-infected individuals is scarce. The present study assessed Schistosoma haematobium and STH infection and morbidity patterns among school children in a hyper-endemic focus in the Tana River delta of coastal Kenya.

METHODS

Two hundred and sixty-two children aged 5-12 years from two primary schools were enrolled in the study. For each child, urine was examined for S. haematobium eggs and haematuria, stool was examined for STH eggs, peripheral blood was examined for eosinophilia and haemoglobin level, the urinary tract was ultrasound-examined for S. haematobium-related pathology, and the height and weight was measured and used to calculate the body mass index (BMI).

RESULTS

Prevalences of S. haematobium, hookworm, T. trichiura and A. lumbricoides infection were 94, 81, 88 and 46 %, respectively. There was no significant association between S. haematobium and STH infection but intensity of hookworm infection significantly increased with that of T. trichiura. Lower BMI scores were associated with high intensity of S. haematobium (difference =-0.48, p > 0.05) and A. lumbricoides (difference =-0.67, p < 0.05). Haematuria (both macro and micro) was common and associated with S. haematobium infection, while anaemia was associated with high intensity of S. haematobium (OR = 2.08, p < 0.05) and high hookworm infections OR = 4.75; p < 0.001). The majority of children had eosinophilia, which was significantly associated with high intensity of hookworm infection (OR = 5.34, p < 0.05). Overall 38 % of the children had ultrasound-detectable urinary tract morbidity, which was associated with high intensity of S. haematobium infection (OR = 3.13, p < 0.05).

CONCLUSION

Prevalences of S. haematobium and STH infections among the primary school children were high and the parasites were responsible for significant morbidity. A clear synergistic interaction was observed between hookworm and T. trichiura infections. Increased coverage in administration of praziquantel and albendazole in the area is recommended to control morbidity due to these infections.

Urinary cytokines in Schistosoma haematobium-infected schoolchildren from Tana Delta District of Kenya

BACKGROUND

Pathological changes due to infection with Schistosoma haematobium include cytokine-mediated urinary tract inflammation. The involved cytokines may be excreted in urine and their presence in urine may therefore reflect S. haematobium-related urinary tract pathology. The present study, for the first time, reports on the relationship between selected cytokines in urine and infection with S. haematobium in children from an area highly affected by this parasite.

METHODS

Children aged 5-12 years from two primary schools in Tana Delta District of Kenya were examined for S. haematobium eggs using urine filtration technique, for haematuria using dipstix and for eosinophil cationic protein (ECP), IL-6, IFN- γ, TNF-α and IL-10 levels using ELISA, and for S. haematobium-related urinary tract pathology using ultrasonography. In addition, venous blood was examined for serum IL-6, IFN- γ, TNF-α and IL-10 levels using ELISA.

RESULTS

There was no significant correlation between urinary and serum levels of IL-6, IFN- γ, TNF-α or IL-10. There was no significant difference in geometric mean intensity (GMI) in any of the serum cytokines, or in urinary TNF-α or IFN-γ, between children with light and heavy S. haematobium infections. However, children with heavy S. haematobium infections had significantly higher GMI of urinary IL-6 (p < 0.001) and lower GMI of urinary IL-10 (p = 0.002) than children with light infections. There was also a significant positive correlation between urinary IL-6 and urinary ECP (p < 0.001) and a significant negative correlation between urinary IL-10 and urinary ECP (p = 0.012).

CONCLUSION

Urinary IL-6 was positively correlated to and IL-10 was negatively correlated to infection intensity and urinary tract inflammation in S. haematobium-infected children. Urinary IL-6 and IL-10 ELISA may be a useful non-invasive tool to complement the already available tools for studying S. haematobium-related urinary tract pathology in children.

Comparing parasitological vs serological determination of Schistosoma haematobium infection prevalence in preschool and primary school-aged children: implications for control programmes

To combat schistosomiasis, the World Health Organization (WHO) recommends that infection levels are determined prior to designing and implementing control programmes, as the treatment regimens depend on the population infection prevalence. However, the sensitivity of the parasitological infection diagnostic method is less reliable when infection levels are low. The aim of this study was to compare levels of Schistosoma haematobium infection obtained by the parasitological method vs serological technique. Infection levels in preschool and primary school-aged children and their implications for control programmes were also investigated. Infection prevalence based on serology was significantly higher compared with that based on parasitology for both age groups. The difference between infection levels obtained using the two methods increased with age. Consequentially, in line with the WHO guidelines, the serological method suggested a more frequent treatment regimen for this population compared with that implied by the parasitological method. These findings highlighted the presence of infection in children aged ⩽5 years, further reiterating the need for their inclusion in control programmes. Furthermore, this study demonstrated the importance of using sensitive diagnostic methods as this has implications on the required intervention controls for the population.

Measuring morbidity associated with urinary schistosomiasis: assessing levels of excreted urine albumin and urinary tract pathologies

Background

Urinary schistosomiasis is responsible for a variety of debilitating conditions; foremost perhaps are urinary tract pathologies (UTPs). Although portable ultrasonography can be used to detect UTPs visually, there is still a need for rapid morbidity assessment (henceforth referred to as RaMA) tools that can be deployed in the field during implementation, monitoring and evaluation of control programmes. We therefore aimed to determine associations between excreted urine-albumin, as measured using a HemoCue photometer, and UTPs, as detected by ultrasonography, in children and adults from an urinary schistosomiasis endemic area in Zanzibar.

Methodology/Principal Findings

In a survey of 140 school-children of both sexes (aged 9 to 15 yr) and 47 adult males (≥16 yr) on the island of Unguja, the prevalence of egg-patent urinary schistosomiasis was 36.4% (CI₉₅ 28.5–45.0%) and 46.8% (CI₉₅ 32.1–61.9%) (P = 0.14), and that of UTPs was 39.4% (CI₉₅ 31.0–48.3%) and 64.4% (CI₉₅ 48.8–78.1%) (P = 0.006), respectively. In school-children, raised urine-albumin concentrations (>40 mg/L) were associated, albeit non-significantly, with prevalence of infection (OR = 3.1, P = 0.070), but more specifically and significantly with the prevalence of micro-haematuria (OR = 76.7, P<0.0001). In adults, elevated urine-albumin excretion was associated with UTPs, particularly lesions of the bladder wall (OR = 8.4, P = 0.013). Albuminuria showed promising diagnostic performance, especially in school-aged children with sensitivity of 63.3% and specificity of 83.1% at detecting lower UTPs, i.e. bladder-wall lesions (ultrasonography as ‘gold standard’).

Conclusion/Significance

This study indicates that albuminuria assays could be used as a RaMA tool for monitoring UTP prevalence during control programmes, as well as a tool for selecting those with more chronic bladder-wall lesions without resorting to ultrasonography.

Urinary schistosomiasis is a debilitating disease caused by a parasitic worm that dwells in the blood vessels, particularly those surrounding the human bladder wall. Although not directly associated with high patient mortality, this disease is linked to both short-term morbidity, e.g. visible blood in urine (acute), as well as long-term sequelae, e.g. urinary tract pathologies (chronic). Numerous control programmes based upon chemotherapy have been implemented in sub-Saharan Africa in an attempt to reduce the burden of disease inflicted, particularly in children. Although there are rapid tests to assess the prevalence of acute manifestations of disease (i.e. blood in urine), namely urine-reagent strips, monitoring of chronic manifestations (i.e. urinary tract pathologies) is still rather laborious, time-consuming and requires specialised equipment, e.g. portable ultrasonography, as well as highly trained staff. This study has attempted to evaluate associations between albuminuria (albumin in urine, a new application for the HemoCue photometer) and urinary tract pathologies, and consequently assess this new biochemical marker as a potential rapid proxy of chronic disease sequelae typical in children in areas where urinary schistosomiasis is of public health importance.

Urinary schistosomiasis-associated morbidity in schoolchildren detected with urine albumin-to-creatinine ratio (UACR) reagent strips

OBJECTIVE

To evaluate urine albumin-to-creatinine ratio (UACR) reagent strips for detection of urinary tract pathology (UTP) associated with urinary schistosomiasis in schoolchildren from Zanzibar.

PATIENTS AND METHODS

Sixty-six schoolchildren were examined for urinary schistosomiasis and UTP using urine reagent strips (Hemastix, urine microscopy and portable ultrasonography. The UACR was estimated using Microalbustix; univariate and logistic regression methods were used to test for statistical associations.

RESULTS

Prevalence of egg-patent schistosomiasis was 65.2% while 77.3% had micro-haematuria and 66.1% had a least one ultrasound-identified UTP. Abnormal UACR (> or =3.4 mg/mmol) was frequent (88.4%) but an unsatisfactory identifier of UTP, albeit highly sensitive: sensitivity (SS) = 100.0%, specificity (SP) = 23.8%, positive predictive value (PPV) = 71.9%, negative predictive value (NPV) = 100.0%. When only severely abnormal UACR was considered (> or =33.9 mg/mmol), SS decreased while SP improved: SS = 58.5%, SP = 61.9%, PPV = 75.0%, NPV = 43.3%.

CONCLUSION

Abnormal and severely abnormal UACRs were strongly associated with egg-patent urinary schistosomiasis and UTP, although via different mechanisms: respectively, from venous blood released directly into the urine from bladder wall perforations, and from leaching sera released from chronic egg-induced lesions throughout the urinary tract. From a control perspective, Microalbustix reagent strips are therefore best applied in pre-screening protocols allowing selection, or rather confident exclusion, of schoolchildren with urinary schistosomiasis for more detailed investigations.

Evaluation and application of potential schistosome-associated morbidity markers within large-scale mass chemotherapy programmes

A primary objective of schistosomiasis control programmes is to achieve, and hence also demonstrate, a quantifiable reduction in schistosome-associated morbidity as a consequence of chemotherapeutic intervention. Inherent within such an objective, it is necessary to define and validate direct and indirect indicators of schistosome-related morbidity. However, to define and thereby document such morbidity, and its reduction following treatment, may not be straightforward, particularly for intestinal schistosomiasis-induced morbidity, which is often not apparent in all but the most severe or chronic cases. Within all 'Schistosomiasis Control Initiative' activities, across selected sub-Saharan African countries since 2002, a range of standard and novel potential morbidity markers have been monitored and evaluated. Parasitological intensity measures, combined with haemoglobin/anaemia counts and ultrasonography, proved valuable schistosomiasis-related morbidity indicators, being both logistically practical and informative. Additional measures tested, such as albumin excretion profiles, were promising, and are subject to ongoing research, whilst some measures, such as distended stomach/umbilical circumference, anthropometrics and health questionnaires proved less reliable. These results serve to both illustrate the success of current control activities in reducing schistosome-induced morbidity, and to highlight key tools and techniques for continued application within ongoing and future mass drug administration programmes.

Validation of the World Health Organization's Rapid Assessment method for urinary schistosomiasis in southeastern Nigeria

Urinary schistosomiasis is a helminth disease that causes high morbidity in endemic areas of tropical and subtropical regions. Efforts are being made to evolve a cost-effective method for diagnosing the infection in large populations. A study supported by the World Health Organization (WHO) has established the Rapid Assessment (Questionnaire) method in which diagnosis is based on the respondent's ability to answer yes to the presence of hematuria. This method has been validated in some African countries and elsewhere. The aim of the present study was to validate the Rapid Assessment method in a community in southeastern Nigeria where the disease is endemic. A survey was carried out using both the parasitological diagnosis of the presence of the characteristic egg of Schistosoma haematabium in urine samples and the WHO Rapid Assessment method. Positive results in the 2 methods were calculated as percentages, and a correlation analysis of the percentages was done using product moment statistics. This gave a significant value of r = 2.9435 (P < 0.05). Sex-related prevalence was observed at significant correlation values of r = 1.0011 and r = 1.574 (P < 0.05). The diagnostic performance of the Rapid Assessment method was calculated using Baker's procedure method. A high sensitivity of 93.4%, specificity of 99%, positive predictive value of 96.6%, and negative predictive value of 99.4% were calculated. The consistent high correction performance values confirm that the Rapid Assessment method may be a useful alternative to the parasitological tests for use in schools and community surveys in identifying high-risk individuals for urinary schistosomiasis in southeastern Nigeria.

Evolutionary concepts in predicting and evaluating the impact of mass chemotherapy schistosomiasis control programmes on parasites and their hosts

Schistosomiasis is a parasitic disease of significant medical and veterinary importance in many regions of the world. Recent shifts in global health policy have led towards the implementation of mass chemotherapeutic control programmes at the national scale in previously 'neglected' countries such as those within sub-Saharan Africa. Evolutionary theory has an important role to play in the design, application and interpretation of such programmes. Whilst celebrating the rapid success achieved to date by such programmes, in terms of reduced infection prevalence, intensity and associated human morbidity, evolutionary change in response to drug selection pressure may be predicted under certain circumstances, particularly in terms of the development of potential drug resistance, evolutionary changes in parasite virulence, transmission and host use, and/or competitive interactions with co-infecting pathogens. Theoretical and empirical data gained to date serve to highlight the importance of careful monitoring and evaluation of parasites and their hosts whenever and wherever chemotherapy is applied and where parasite transmission remains.

Urinary schistosomiasis: an uncommon cause of gross hematuria in the industrialized countries

Schistosomiasis is a parasitic disease that can cause significant illness in humans. While schistosomiasis is not found in the United States and other developed countries, 200 million people are infected worldwide. It is estimated that 400,000 infected persons immigrate to the United States and present to emergency departments with either acute or chronic schistosomiasis. Schistosomiasis can be expected to be seen with increasing frequency in the United States and other developed countries with the continuing influx of immigrants, as well as the return of travelers and soldiers from endemic areas. Although there are several etiologies of gross hematuria in children, schistosomiasis is an uncommon cause of gross hematuria in the industrialized world. The purpose of this report is to bring awareness to health-care providers in the United States and other developed countries of this uncommon cause of gross hematuria, as prompt diagnosis and treatment can result in quick resolution of symptoms.

Human schistosomiasis

Schistosomiasis or bilharzia is a tropical disease caused by worms of the genus Schistosoma. The transmission cycle requires contamination of surface water by excreta, specific freshwater snails as intermediate hosts, and human water contact. The main disease-causing species are S haematobium, S mansoni, and S japonicum. According to WHO, 200 million people are infected worldwide, leading to the loss of 1.53 million disability-adjusted life years, although these figures need revision. Schistosomiasis is characterised by focal epidemiology and overdispersed population distribution, with higher infection rates in children than in adults. Complex immune mechanisms lead to the slow acquisition of immune resistance, though innate factors also play a part. Acute schistosomiasis, a feverish syndrome, is mostly seen in travellers after primary infection. Chronic schistosomal disease affects mainly individuals with long-standing infections in poor rural areas. Immunopathological reactions against schistosome eggs trapped in the tissues lead to inflammatory and obstructive disease in the urinary system (S haematobium) or intestinal disease, hepatosplenic inflammation, and liver fibrosis (S mansoni, S japonicum). The diagnostic standard is microscopic demonstration of eggs in the excreta. Praziquantel is the drug treatment of choice. Vaccines are not yet available. Great advances have been made in the control of the disease through population-based chemotherapy but these required political commitment and strong health systems.

Hematuria in children due to schistosomiasis in a nonendemic setting

Infection with Schistosoma hematobium is common in immigrants from tropical Africa and commonly presents with painless hematuria. Since chronic, heavy infection can lead to significant morbidity, it is imperative for clinicians who serve the immigrant and refugee population to become familiar with this traditionally exotic disease. Increased awareness will allow earlier diagnosis and treatment of infection, avoiding complications and minimizing expensive and invasive diagnostic procedures.

Urinary schistosomiasis on Zanzibar: application of two novel assays for the detection of excreted albumin and haemoglobin in urine

As part of a urinary schistosomiasis control programme on Zanzibar, an aged cross-sectional survey of 305 children from three schools on Unguja was conducted to investigate the relationships between levels of excreted albumin and haemoglobin in urine and Schistosoma haematobium infection status. Diagnosis was determined by standard parasitological methods, dipstick reagents for microhaematuria, visual inspection for macrohaematuria as well as collection of case-history questionnaire data for self-diagnosis. Prevalence of infection as determined by parasitology was 53.9% and approximately, one quarter of the children examined were anaemic (<11 g dl(-1)). A statistically significant negative association of blood haemoglobin levels of boys and S. haematobium infection intensity status was observed (rs=-0.23, P=0.005). Through sensitivity analysis of urine-albumin values it was determined that a concentration of above >40 mg l(-1), as measured with the HemoCue urine-albumin photometer, had sensitivity, specificity, positive and negative predictive values of 0.90, 0.83, 0.86 and 0.89 respectively against 'gold-standard' parasitology. There was a clear association of reported pain upon micturition for children with elevated urine-albumin levels, with an odds ratio of 20 to 1. Levels of excreted blood in urine were quantified with the HemoCue Plasma/Low Hb photometer. However, dipsticks remain the method of choice for urine-haemoglobin of 0.1 g l(-1) and below. Urine parameters over a 24-h period were assessed in a small sub-sample. Reductions in both albumin and haemoglobin excretion were observed in 11 children 54 days after praziquantel treatment. It was concluded that these rapid, high-through-put, portable HemoCue assays could play a role in better describing and monitoring the occurrence, severity and evolution of urinary schistosomiasis disease. The urine-albumin assay has particular promise as a biochemical marker of S. haematobium induced kidney- and upper urinary tract-morbidity.

Parasitic central nervous system infections in immunocompromised hosts

Immunosuppression due to therapy after transplantation or associated with HIV infection increases susceptibility to various central nervous system (CNS) infections. This article discusses how immunosuppression modifies the presentation, diagnosis, and treatment of selected parasitic CNS infections, with a focus on toxoplasmosis, Chagas disease, neurocysticercosis, schistosomiasis, and strongyloidiasis.

Treatment and re-treatment strategies for schistosomiasis control in different epidemiological settings: a review of 10 years' experiences

This paper reviews 10 years' experience with schistosomiasis control in different endemic settings in Africa, Asia and the Americas. Research projects, pilot programs and long-term large-scale programs with the objective of controlling morbidity have been included in the review. Major advances in diagnostic tools and rapid assessment techniques have evolved during the decade making it possible to follow changes in pathology after treatment and to get baseline epidemiological information at very low cost. At the same time prices of drugs like praziquantel has declined dramatically (to <US dollar 0.10 per tablet). Equipment for indicators of morbidity due to Schistosoma haematobium (e.g. urine reagent strips for micro-haematuria) have also become cost-effective. Cheap and simple parasitological methods for examination of urine and stool specimens have now been available for almost two decades. The impact of different control strategies on morbidity and the duration of the effects on pathology have been reviewed and suggestions for new treatment and re-treatment strategies are made based on the existing experience from different regions and countries.

Schistosomiasis: from risk assessment to control

In this article, an account of some of the hot areas in schistosomiasis research is given, emphasizing what has been achieved during the past several years in impact assessment and identifying the research frontiers where further action is needed.