Sensitivity, specificity and positive predictive value of selected clinical signs and symptoms associated with schistosomiasis mansoni

Paediatric schistosomiasis: What we know and what we need to know

Schistosomiasis affects over 200 million people worldwide, most of whom are children. Research and control strategies directed at preschool-aged children (PSAC), i.e., ≤5 years old, have lagged behind those in older children and adults. With the recent WHO revision of the schistosomiasis treatment guidelines to include PSAC, and the recognition of gaps in our current knowledge on the disease and its treatment in this age group, there is now a concerted effort to address these shortcomings. Global and national schistosome control strategies are yet to include PSAC in treatment schedules. Maximum impact of schistosome treatment programmes will be realised through effective treatment of PSAC. In this review, we (i) discuss the current knowledge on the dynamics and consequences of paediatric schistosomiasis and (ii) identify knowledge and policy gaps relevant to these areas and to the successful control of schistosome infection and disease in this age group. Herein, we highlight risk factors, immune mechanisms, pathology, and optimal timing for screening, diagnosis, and treatment of paediatric schistosomiasis. We also discuss the tools required for treating schistosomiasis in PSAC and strategies for accessing them for treatment.

Biosocial Determinants of Persistent Schistosomiasis among Schoolchildren in Tanzania despite Repeated Treatment

Schistosomiasis is a parasitic disease endemic to Tanzania and other countries of the global south, which is currently being addressed through preventive chemotherapy campaigns. However, there is growing recognition that chemotherapy strategies will need to be supplemented to sustainably control and eventually eliminate the disease. There remains a need to understand the factors contributing to continued transmission in order to ensure the effective configuration and implementation of supplemented programs. We conducted a cross-sectional questionnaire, to evaluate the biosocial determinants facilitating the persistence of schistosomiasis, among 1704 Tanzanian schoolchildren residing in two districts undergoing a preventive chemotherapeutic program: Rufiji and Mkuranga. A meta-analysis was carried out to select the diagnostic questions that provided a likelihood for predicting infection status. We found that self-reported schistosomiasis continues to persist among the schoolchildren, despite multiple rounds of drug administration.Using mixed effects logistic regression modeling, we found biosocial factors, including gender, socio-economic status, and water, sanitation, and hygiene (WASH)-related variables, were associated with this continued schistosomiasis presence. These findings highlight the significant role that social factors may play in the persistence of disease transmission despite multiple treatments, and support the need not only for including integrated technical measures, such as WASH, but also addressing issues of poverty and gender when designing effective and sustainable schistosomiasis control programs.

Meta-analysis of the diagnostic efficiency of the questionnaires screening for schistosomiasis

Schistosomiasis is the second widespread tropical disease that affects the health of over 240 million people of 78 countries. Questionnaires have been commonly used to diagnose schistosomiasis, while no meta-analysis of their efficacy had been reported previously. This meta-analysis was conducted to assess their diagnostic accuracy of schistosomiasis. Studies published prior to December 1, 2014, that had used questionnaires as a diagnostic tool were searched in PubMed, Medline, EMBASE, and China National Knowledge Infrastructure (CNKI) database. A total of 32 studies with 72,812 cases were identified for the meta-analysis. The best diagnostic odds ratio (DOR) was obtained from Schistosoma haematobium (67.68, 95 % confidence interval (CI) = 31.48 to 145.54), followed by Schistosoma japonicum (11.74, 95 % CI = 4.59 to 30.05) then Schistosoma mansoni (2.98, 95 % CI = 1.95 to 4.54). Pooled sensitivity and specificity were respectively 0.82, 0.88, and 0.46, and 0.59, 0.86, and 0.81 for S. japonicum, S. haematobium, and S. mansoni. The multivariable subgroup analyses showed that the questionnaires which had been pretested and standardized had better diagnostic performance. The result suggested that questionnaires can be used to diagnose schistosomiasis with moderate sensitivity and specificity and the questionnaires for diagnosing S. haematobium performed best.

Human schistosomiasis

Human schistosomiasis--or bilharzia--is a parasitic disease caused by trematode flukes of the genus Schistosoma. By conservative estimates, at least 230 million people worldwide are infected with Schistosoma spp. Adult schistosome worms colonise human blood vessels for years, successfully evading the immune system while excreting hundreds to thousands of eggs daily, which must either leave the body in excreta or become trapped in nearby tissues. Trapped eggs induce a distinct immune-mediated granulomatous response that causes local and systemic pathological effects ranging from anaemia, growth stunting, impaired cognition, and decreased physical fitness, to organ-specific effects such as severe hepatosplenism, periportal fibrosis with portal hypertension, and urogenital inflammation and scarring. At present, preventive public health measures in endemic regions consist of treatment once every 1 or 2 years with the isoquinolinone drug, praziquantel, to suppress morbidity. In some locations, elimination of transmission is now the goal; however, more sensitive diagnostics are needed in both the field and clinics, and integrated environmental and health-care management will be needed to ensure elimination.

Schistosoma mansoni-related morbidity in a low-prevalence area of Brazil: a comparison between egg excretors and seropositive non-excretors

In areas where there is a low prevalence of schistosomiasis mansoni, faecal examination is a relatively insensitive method of detection and infected people may also be missed because most show only mild morbidity. In such settings, serology may be a more useful diagnostic tool than microscopy. In the present study, the clinical and biochemical characteristics of individuals who were stool-positive for Schistosoma mansoni eggs were compared with those of individuals, from the same low-prevalence area of Brazil, who were stool-negative but seropositive for the parasite. Overall, 269 subjects were checked both for schistosome eggs in their faeces (using Kato-Katz smears and Lutz sedimentation) and for anti-S. mansoni IgG in their sera (using an ELISA). Although 128 (48%) of these subjects were found seropositive, only 26 (10%) were found to be egg excretors and two of the egg excretors were seronegative. Compared with the seropositive egg-negatives, the egg excretors had significantly higher frequencies of fatigue, melaena, jaundice and swelling of the abdomen. The egg excretors also had higher frequencies of hepatomegaly (20% v. 16%) and splenomegaly (4% v. 1%). In both groups of subjects, mean concentrations of serum proteins and haemoglobin and mean leucocyte counts were in the normal range whereas most blood concentrations of alanine aminotransferase and many of those of aspartate aminotransferase were slightly elevated. Although the egg excretors tended to have low-intensity infections, it seems possible that the seropositive nonexcretors had even milder infections that could not be detected by faecal examination. The high frequency of cure observed when the egg excretors were given praziquantel at 40 mg/kg (94%) is probably another indication that most had light infections when they were treated.

Fecal occult blood test and gastrointestinal parasitic infection

Stool specimens of 1238 workers in western region of Saudi Arabia were examined for infection with intestinal parasites and for fecal occult blood (FOB) to investigate the possibility that enteroparasites correlate to occult intestinal bleeding. Direct smears and formal ether techniques were used for detection of diagnostic stages of intestinal parasites. A commercially available guaiac test was used to detect fecal occult blood. 47.01% of the workers were infected with intestinal parasites including eight helminthes species and eight protozoan species. The results provided no significant evidence (P-value = 0.143) that intestinal parasitic infection is in association with positive guaiac FOB test.

Large scale evaluation of WHO's ultrasonographic staging system of schistosomal periportal fibrosis in Ethiopia

OBJECTIVES

To evaluate the recent WHO's ultrasonographic diagnostic staging system of schistosomal periportal thickening/fibrosis and to assess intra/inter-observer variation associated with its use.

METHODS

Local standard of portal branch wall thickness (PBWT) for height was established using 150 healthy subjects. Intra and inter-observer variation in image pattern identification and PBWT measurements were assessed in 94 and 35 subjects, respectively, with differing stages of periportal thickening fibrosis. WHO's diagnostic criteria were evaluated in 2,451 community members (1,277 males, 1,174 females; mean age 18.8 years) with an overall Schistosoma mansoni prevalence estimate of 65.9%.

RESULTS

There were no significant inter/intra-observer variations in image pattern identification and PBWT measurements. Based on Ethiopian PBWT-for-height standard, 128/2,451 (5.2%) had insipient, 46/2,451 (1.9%) had possible/probable and 112/2451 (4.6%) had definite/advanced periportal thickening/fibrosis. Comparable figures were obtained using the Senegalese PBWT-for-height standard and there was good agreement between Ethiopian and Senegalese healthy control-based diagnostic criteria in classifying the 286 subjects into stages of periportal thickening/fibrosis (kappa = 0.87, P < 0.001).

CONCLUSIONS

With further improvement, the WHO's ultrasonographic diagnostic criteria can be used in health institutions and community surveys. Image pattern based assessment is simple and more reproducible than PBWT based assessment of periportal thickening/fibrosis. The latter is, however, more useful in clarifying the status of an individual with doubtful image pattern, and in monitoring post-treatment outcome of periportal thickening/fibrosis. Considering the comparability of PBWT-for-height standards, setting one international standard of PBWT-for-height is more practical than developing local standards for each endemic area.

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.

The impact of chemotherapy on morbidity due to schistosomiasis

Current knowledge on the impact of chemotherapy on schistosomiasis-related morbidity is still fragmentary. In urinary schistosomiasis, reversal of organ pathology follows cure after 6 months and resurgence takes place after at least another 6 months. Retreatment after less than 1 year is, therefore, unnecessary. Also, intestinal schistosomiasis appears to regress promptly after chemotherapy. For the reversal of hepatic morbidity, more than one chemotherapy round appears necessary at least in foci of intense transmission of schistosomiasis. The earlier chemotherapy is given, the higher the chances of reversal of schistosomal pathology, but pathology may regress to some extent also in adults. The regression and resurgence of periportal fibrosis, as detected by ultrasonography, occurs with a delay of 7 months to more than 2 years after therapy. Retreatment after less than 1 year may not permit full assessment of the impact of the first round on hepatic morbidity. Children and adolescents should be the major target population, taking into account that in many foci, children out-of-school must be covered because they are at the highest risk. Repeated treatment during childhood may prevent the development of urinary tract disease in adulthood. However, no data are available on the prevention of genital pathology. Repeated chemotherapy may have a long term effect on re-infection intensities and the development of severe morbidity, even in foci where control has been interrupted for many years. Severe hepatic fibrosis may be prevented even in foci of intense transmission provided more than two rounds of chemotherapy have been given in childhood and that chemotherapy is available on demand. Chemotherapy has an important impact on child development, physical fitness and working capacity. Its effect on growth and anemia is improved by simultaneous treatment of intestinal parasites and the provision of adequate iron supplementation. The impact of chemotherapy on many of the multifaceted manifestations of schistosomiasis has not been assessed systematically. More data are needed on gallbladder pathology, neuroschistosomiasis, endocrinologic disorders, bladder cancer and co-infections with other pathogens. In areas where control has been achieved, the overall morbidity and mortality has decreased with a delay of many years or even decades.

Simple school questionnaires can map both Schistosoma mansoni and Schistosoma haematobium in the Democratic Republic of Congo

The use of self-administered questionnaires has been shown in different African countries to be inexpensive and reliable for the rapid identification of communities at highest risk of urinary schistosomiasis. For intestinal schistosomiasis due to Schistosoma mansoni there is a clear need for a similar approach. We report the results from a large-scale study undertaken in the western part of the Democratic Republic of Congo (DRC, formerly Zaire). Within 4 weeks questionnaires were correctly completed in 136 out of 160 schools (85%). In 57 of these schools children were screened for infections with schistosomes and geohelminths. The prevalence of 'schistosomiasis' as reported in the questionnaires showed the best correlation with the prevalence of S. mansoni infections (r = 0.77, P < 0.0001). Calculations of the diagnostic performance of reported 'schistosomiasis' to detect schools with a high risk of intestinal schistosomiasis gave positive predictive values of 87 and 62%, and negative predictive values of 74 and 87% for moderate and high infection thresholds, respectively. Reported 'blood in stool' was another useful indicator for intestinal schistosomiasis. Reported 'blood in urine' showed the best correlation with urinary schistosomiasis (r = 0.75, P < 0.001) and the positive predictive values were 81 and 50%, and the negative predictive values were 89 and 95% for moderate and high infection thresholds, respectively. We conclude that school children in DRC have a distinct perception of intestinal and urinary schistosomiasis and that questionnaires could be useful to identify high-risk schools for both parasites.

Schistosoma mansoni, intestinal parasites and perceived morbidity indicators in schoolchildren in a rural endemic area of western Côte d'Ivoire

There is a great need for rapid and low-cost identification of communities at high risk of intestinal schistosomiasis. We report the development of a questionnaire approach that may do so. In the first phase, 209 schoolchildren from 3 neighbouring villages in a rural area endemic for intestinal schistosomiasis in western Côte d'Ivoire were screened for Schistosoma mansoni and other helminths on 4 consecutive days using Kato-Katz thick smears. Daily infection prevalences of S. mansoni were high (60%-71%) and the cumulative infection prevalence was 92.3%. Infections with hookworms and Ascaris lumbricoides were also frequent, with cumulative prevalences of 60.8% and 38.3%, respectively. On day 3, the presence of Entamoeba histolytica/E. dispar and Giardia lamblia was assessed by a faecal concentration procedure. In the second phase, focus group discussions (FGD) were conducted: in each village one FGD with heavily infected children and one FGD with lightly or S. mansoni-uninfected schoolchildren to assess their perception of morbidity. The aim was to establish local terms indicating S. mansoni infections. 'Diarrhoea', 'blood in the stools', 'stomach disorders' and 4 terms in the local Yacouba/Dioula languages were frequently used by infected children. A simple questionnaire was then developed and the headteachers interviewed all schoolchildren individually. 'Blood in stools', gnon and toto were reported significantly more frequently among moderately and heavily S. mansoni-infected children than by those not or only lightly infected. The term gloujeu indicated borderline significance. The best diagnostic performance was found for 'blood in stool' (sensitivity: 47%; specificity: 76%; positive predictive value: 66%; negative predictive value: 60%). All schistosomiasis infections were treated with a single oral dose of praziquantel (40 mg/kg body weight) and the same questionnaire was re-administered 6 weeks post-treatment. Statistically significantly less children reported having had 'blood in stool' and 'gloujeu' after treatment (McNemar's (chi2-test, P < 0.01). We conclude that 'blood in stool', 'gnon', 'toto' and 'gloujeu' are the most reliable reported symptoms for rapid and low-cost identification of communities that are at high risk of S. mansoni infections in Côte d'Ivoire.

The use of morbidity questionnaires to identify communities with high prevalences of schistosome or geohelminth infections in Tanzania

Parasitic infections were investigated in Morogoro Rural District, Tanzania, between October 1992 and June 1993. A total of 4589 schoolchildren (aged 7-17 years) from 30 primary schools was screened for infection with Ascaris lumbricoides, Trichuris trichiura, hookworms (3456 children only), Schistosoma mansoni and S. haematobium. The children were also asked about their recent experiences of the following: diarrhoea, abdominal pain, blood in stool, perception of suffering from schistosomiasis, and worm infection and examined for spleen and liver enlargement. Among schools, there were correlations between the prevalence of S. mansoni infection and bloody stools, spleen enlargement and liver enlargement, and between S. haematobium infection and the presence of blood in urine. To exclude ecological explanations for the correlations, logistic regression was used to estimate the adjusted odds ratio (OR) for each infection and each sign or symptom. No sign or symptom was significantly associated with any geohelminth infection. Reported blood in stool was significantly associated with S. mansoni infection (OR = 1.62, P = 0.045). Reported blood in urine was significantly associated with S. haematobium infection (OR = 7.71, P < 0.001), as was reported blood in stool (OR = 11.52, P < 0.001), indicating that presence of blood in either form of excreta was related to the local term for schistosomiasis. These results support the possibility of using reported blood in stool as a means of rapid assessment for identifying communities with a high prevalence of S. mansoni infection.

Questionnaires in the screening for Schistosoma mansoni infection: a study of socio demographic and water contact variables in four communities in Brazil

The use of questionnaires has been recommended for identifying, at a lower cost, individuals at risk for schistosomiasis. In this study, validity of information obtained by questionnaire in the screening for Schistosoma mansoni infection was assessed in four communities in the State of Minas Gerais, Brazil. Explanatory variables were water contact activities, sociodemographic characteristics and previous treatment for schistosomiasis. From 677, 1474, 766 and 3290 individuals eligible for stool examination in the communities, 89 to 97% participated in the study. The estimated probability of individuals to be infected, if they have all characteristics identified as independently associated with S.mansoni infection, varied from 15% in Canabrava, to 42% in Belo Horizonte, 48% in Comercinho and 80% in São José do Acácio. Our results do not support the hypothesis that a same questionnaire on risk factors could be used in screening for S.mansoni infection in different communities.

Effect of skin colour and selected physical characteristics on Schistosoma mansoni dependent morbidity

The effect of the colour group on the morbidity due to Schistosoma mansoni was examined in two endemic areas situated in the State of Minas Gerais, Brazil. Of the 2773 eligible inhabitants, 1971 (71.1%) participated in the study: 545 (27.6%) were classified as white, 719 (36.5%) as intermediate and 707 (35.9%) as black. For each colour group, signs and symptoms of individuals who eliminated S.mansoni eggs (cases) were compared to those who did not present eggs in the faeces (controls). The odds ratios were adjusted by age, gender, previous treatment for schistosomiasis, endemic area and quality of the household. There was no evidence of a modifier effect of colour on diarrhea, bloody faeces or abdominal pain. A modifier effect of colour on hepatomegaly was evident among those heaviest infected (> or = 400 epg): the adjusted odds ratios for palpable liver at the middle clavicular and the middle sternal lines were smaller among blacks (5.4 and 6.5, respectively) and higher among whites (10.6 and 12.9) and intermediates (10.4 and 10.1, respectively). These results point out the existence of some degree of protection against hepatomegaly among blacks heaviest infected in the studied areas.

Sonographic features of portal hypertension in schistosomiasis mansoni

The diagnostic value of real-time sonography in the study of portal hypertension was assessed in 66 patients with hepatosplenic schistosomiasis mansoni, all with Symmers's fibrosis and esophageal varices. Seventy-one individuals without schistosomiasis were selected as controls. The inner diameters of the portal vessels were measured by sonography in all patients and controls: splenoportography was also performed in the schistosomal group. Intra-splenic pressure was over 30 cm of water in 44 of 60 patients with schistosomiasis. The upper limit of normality for portal vessel diameters was set through receiver operating characteristic curve at 12 mm for portal vein, 9 mm for splenic vein at splenic hilus, and 9 mm for superior mesenteric vein. The best discriminative vein for the diagnosis of portal hypertension was the splenic vein followed by the portal vein. A direct correlation was observed between the diameter of the splenic vein, measured by sonography, and the intra-splenic pressure. Except for the paraumbilical and mesenteric veins, more frequently identified by sonography, there was no statistical difference in the frequency of visualization of splanchnic vessels by sonography or splenoportography.

A community-based randomized trial of praziquantel to control schistosomiasis morbidity in schoolchildren in Zambia

A community-based, double-blind, randomized trial of praziquantel was carried out in an area of Zambia endemic for schistosomiasis. The aim of the study was to assess the impact of the treatment on Schistosoma mansoni morbidity. A total of 377 infected children, aged seven to 19 years, was randomized into two groups: one of 190 (group A) and one of 187 (group B). All children were treated with 40 mg praziquantel/kg at the start of the study. Six months later, the children in group A were re-treated with the same dose of praziquantel, while the children in group B were given placebos. All children were followed up three, six and 12 months after the initial treatment, morbidity being clinically evaluated at the six- and 12-month follow-ups. The results show that, in both groups of children, there were significant reductions in splenomegaly, hepatomegaly, and subjective symptoms of morbidity six and 12 months after initial treatment. However, there were no significant differences, between the two groups, in the prevalences of these symptoms of morbidity. It therefore appears that once-yearly treatment of children, in this and similar endemic areas, is sufficient to reduce schistosomiasis morbidity to, and maintain it at, a tolerable level.

Diagnostic techniques in schistosomiasis control. A review

Diagnosis is central to all aspects of schistosomiasis. Decisions on individual and community treatment, estimations on prognosis and assessment of morbidity, evaluation of chemotherapy and control measures all require the results from diagnostic tests. Unfortunately, all presently available techniques are characterised by diagnostic imperfections. Selection and application of methods should therefore correspond to the type of information sought by the public health officer or the epidemiologist and interpretation of test results must take into consideration the drawbacks and constraints inherent to each of the various diagnostic approaches.

Epidemiology of Schistosoma mansoni infection in a low-endemic area in Brazil: clinical and nutritional characteristics

A cross-sectional case-control study designed to evaluate the role of malnutrition in the association between the intensity of Schistosoma mansoni infection and clinical schistosomiasis, was conducted in an area with both low frequency of infection and low morbidity of schistosomiasis in Brazil. Cases (256) were patients with a positive stool examination for S. mansoni; their geometrical mean number of eggs/gram of feces was 90. Controls (256) were a random sample of the negative participants paired to the cases by age, sex and length of residence in the area. The clinical signs and symptoms found to be associated with S. mansoni infection, comparing cases and controls, were blood in stools and presence of a palpable liver. A linear trend in the relative odds of these signs and symptoms with increasing levels of infection was detected. Adjusting by the level of egg excretion, the existence of an interaction between palpable liver and ethnic group (white) was suggested. No differences in the nutritional status of infected and non-infected participants were found.

Validity of selected clinical signs and symptoms in diagnosis of Schistosoma mansoni infection

Sensitivity, specificity and positive predictive values of selected clinical signs and symptoms in the diagnosis of Schistosoma mansoni infection were evaluated in 403 individuals (69% of inhabitants over 1 year of age) in an endemic area in Brazil (Divino). Highest sensitivity (13%) was found for blood in stools. Specificity over 90% was found for blood in stools, palpable liver with normal consistency and palpable hardened liver at middle clavicular (MCL) or middle sternal lines (MSL). Hardened liver at MSL (83%) or MCL (75%), and blood in stools (78%) presented higher positive predictive values for S. mansoni infection, while palpable liver with normal consistency at MCL (45%) or MSL (48%) presented smaller values. Enlarged liver without specification of its consistency has been traditionally used as an indicator of the infection in areas where malaria or Kala-azar are not endemic. Our results demonstrate that the probability that a person with blood in stools or hardened palpable liver is infected is higher than among those with palpable liver with normal consistency.