Schistosomiasis mansoni: ultrasound-evaluated hepatic fibrosis and serum concentrations of hyaluronic acid

Schistosomiasis mansoni is a fibrogenic liver disease that constitutes a major health problem in north-eastern Brazil. Although one common manifestation of the disease, periportal fibrosis (PPF), can be assessed by ultrasonography by well-trained physicians, the necessary equipment and personnel are not always readily available. Serum markers, including hyaluronic acid (HA), have been used as alternative means of measuring fibrosis. Recently serum concentrations of HA have been evaluated in 77 Brazilians (61 cases of schistosomiasis mansoni and 16 healthy controls) and compared against the ultrasound-evaluated PPF in the same subjects. The HA was measured using a non-competitive fluorescence-based assay, while the PPF was explored using a portable ultrasound scanner (SSD-500; Aloka, Tokyo) and graded, as patterns A-F, according to the World Health Organization's 'Niamey protocol'. In general, the serum concentrations of HA were found to be positively correlated with the severity of the PPF. The mean concentration of HA in the sera of the 16 controls was significantly lower than that recorded in the schistosomiasis cases who showed PPF of patterns D or E (P<0·001 for each). The cases who showed pattern-C PPF also had significantly less HA in their sera than the cases with PPF of patterns D or E (P<0·001 for each), and the cases with pattern-D fibrosis had significantly lower HA concentrations in their sera than the cases with PPF of pattern E (P<0·001). In an analysis based on a receiver-operating-characteristic (ROC) curve, an HA concentration of 20·2 μg/litre of serum was identified as a threshold that could be used to distinguish moderate cases of PPF (i.e. patterns C or D) from the more advanced cases (i.e. patterns E or F), with a sensitivity of 60% and specificity of 65%. In conclusion, it appears that serum concentrations of hyaluronic acid could be used as markers for periportal fibrosis in patients with schistosomiasis mansoni.     

Circulating adhesion molecules in patients with different clinical forms of S. mansoni infection

Elucidating the mechanisms that regulate the severity of schistosomiasis has been a major research objective over the past several years. In this study, morbidity of S. mansoni infection was assessed using an ultrasonographic staging system of periportal fibrosis of the liver. Sera of S. mansoni infected patients with different clinical forms of the disease were assayed for the presence of intercellular adhesion molecule-1 (ICAM-1), soluble endothelial cell adhesion molecule-1 (sE-selectin), leukocyte adhesion molecule-1 (sL-selectin) and granule membrane protein-140 (P-selectin). Association between serum levels of adhesion molecules and ultrasonographic data was evaluated. Fifty-one subjects with pure hepatic schistosomiasis having ultrasonographic assessment of periportal fibrosis (PPF) were grouped according to the thickness of their portal tracts: simple intestinal =<3mm, grade I=3-5mm, grade II=>5-7mm and grade III=>7mm. Greater diameter of portal vein and larger spleen size were associated with increasing the thickness of portal tract. All groups had elevated levels of slCAM-1 compared with normal controls. Patients in grade III had significantly higher levels of serum slCAM-1 than those in other grades of infection. The sE- and sL-selectin were comparable in the sera of all patient groups. sP-selectin was significantly elevated in the sera of grade II patients compared with other patients of various clinical groups. Positive correlation was recorded between slCAM-1 level and degree of PPF, but not with other adhesion molecules. These data suggested that, the main criteria of diagnosis of S. mansoni infection using ultrasonography include periportal fibrosis, hypertrophy of left hepatic lobe, widening of the portal veins and splenomegaly. slCAM-1 may participate in the pathology associated with schistosomiasis infection. It could be employed as a potential morbidity marker in schistosomiasis mansoni infection.     

Gastro-intestinal symptoms associated with intense Schistosoma mansoni infection affect class-attentiveness of schoolchildren in Ethiopia

Objective

To assess effect of subtle morbidities related to schistosomiasis mansoni on class-attentiveness of schoolchildren.

Methods

A cross-sectional study was undertaken involving 568 schoolchildren (mean age 13.4 years; 333 from Schistosoma mansoni endemic villages (Sille and Worke-Mado) and 235 from the non-endemic town Sheno. A questionnaire on signs and symptoms of ill-health was administered to all study subjects. In addition, parasitological and nutritional anthropometric data were collected. All study subjects from S. mansoni endemic areas were treated with praziquantel and albendazol while children from the non-endemic town were only treated with albendazol.

Findings

Prevalence of S. mansoni infection was 95% in Sille and 90.6% in Worke-Mado. Overall, among schoolchildren from S. mansoni endemic areas, 36.3% were under-nourished; 66.4% reported easy fatigue/listlessness; 61.3% had abdominal cramps with bloody-mucoid stools, and 17.7% reported to have severe and frequent abdominal cramps which distracted their class-attentiveness. The latter two symptoms were significantly associated with intensity of S. mansoni infection. Among schoolchildren from the non-endemic town Sheno, only 8.9% were under-nourished, 20% reported infrequent abdominal cramps and none had symptoms that were severe enough to affect class-attentiveness.

Conclusion

Symptoms associated with intense S. mansoni infection may negatively affect class-attentiveness of schoolchildren which may have important implications on their overall educational achievements. Further detailed intervention-based prospective studies are recommended to validate these findings which, if confirmed, could further justify school-age targeted praziquantel-based control of schistosomiasis.     

Noninvasive diagnosis of periportal fibrosis in schistosomiasis mansoni: A comprehensive review

Schistosomiasis mansoni is a neglected disease and key public health problem, mainly due to its high prevalence, the scarcity of public policies, and the severity of some clinical forms. Periportal fibrosis (PPF) is the commonest complication of chronic schistosomiasis mansoni and its diagnosis requires different techniques. Even though wedge biopsy of the liver is considered the gold standard, it is not justified in non-surgical patients, and percutaneous liver biopsy may be informative but does not have sufficient sensitivity. Noninvasive PPF tests mostly include biological (serum biomarkers or combined scores) or physical assessments (imaging assessment of fibrosis pattern or tissue stiffness). Moreover, imaging techniques, such as ultrasound, computed tomography, magnetic resonance imaging, and elastography are applied not only to support the diagnosis of schistosomiasis, but also to assess and detect signs of portal hypertension and organ damage due to chronic schistosomiasis. A combination between a comprehensive history and physical examination with biomarkers for liver fibrosis and imaging methods seems to offer the best approach for evaluating these patients. In addition, understanding their strengths and limitations will allow a more accurate interpretation in the clinical context and can lead to greater accuracy in estimating the degree of fibrosis in patients with Schistosomiasis mansoni (S. mansoni) infection. This review will discuss the different noninvasive methods that are currently available for the evaluation of PPF in S. mansoni infection, and their application, advantages, and limitations in clinical practice.     

Infection with Schistosoma mansoni correlates with altered immune responses to Ascaris lumbricoides and hookworm

Studies were performed on humoral and cellular immune responses of patients from areas in Brazil endemic for hookworm and Ascaris lumbricoides, and either endemic or non-endemic for Schistosoma mansoni. Humoral and cellular responses were evaluated by enzyme-linked immunosorbant assay (ELISA) and peripheral blood mononuclear cell (PBMC) proliferation assays against larval hookworm antigens, A. lumbricoides egg antigens, and soluble egg antigens (SEA) or soluble whole adult antigenic preparation (SWAP) from S. mansoni. Patients from S. mansoni-endemic areas, who currently had only hookworm or Ascaris infections, expressed lower humoral and cellular responses to hookworm or Ascaris antigens, respectively, than did their counterparts from areas not endemic for S. mansoni. Individuals from S. mansoni endemic area, although without detectable S. mansoni infection, do mount humoral and cellular responses to SEA and SWAP. This group of individuals has been probably in contact with S. mansoni antigens, since the groups harboring A. lumbricoides or hookworm infections from non-S. mansoni endemic areas do not have detectable anti-S. mansoni responses. PBMC proliferative responses discriminated well between patients with active hookworm infections versus ascariasis, if they were from areas not endemic for S. mansoni.     

Absence of cervical schistosomiasis among women from two areas of north-eastern Brazil with endemic Schistosoma mansoni

Genital manifestations in schistosomiasis haematobium are common and are associated with considerable morbidity. Although Schistosoma mansoni may also cause genital disease, the frequency of this complication is not known. Cervical biopsies (N=401) and Pap smears (N=981) were therefore collected from women living in two S. mansoni-endemic areas (in the states of Alagoas and Ceará, in north-eastern Brazil). The women were screened for the presence of sexually transmitted diseases and for the presence, in their cervical smears and/or biopsies, of S. mansoni eggs. Attempts at schistosomiasis control, which began in both study areas in 1977, have led to generally low intensities of infection (<30 eggs/g faeces in 99% of infections) and community prevalences of infection that range between 1% and 52%. As no schistosome ova were detected in any of the biopsies or smears, it appears that the risk, among women, of genital manifestations of S. mansoni infection is small in areas where the parasite load in the population is low (as the result of interventions to control intestinal schistosomiasis).     

Measuring morbidity in schistosomiasis mansoni: relationship between image pattern,portal vein diameter and portal branch thickness in large-scale surveys using new WHO coding guidelines for ultrasound in schistosomiasis

OBJECTIVE: World Health Organization consensus meetings on 'Ultrasound in Schistosomiasis' in 1996 and 1997 anticipated further challenges in the global implementation of a standardized protocol for morbidity assessment in schistosomiasis mansoni. We evaluated the performance of the qualitative and quantitative components of the new Niamey criteria. METHOD: Use of the Niamey protocol among 3954 subjects in two linked, cross-sectional ultrasound surveys of Schistosoma mansoni-endemic populations in Egypt and Kenya. RESULTS: There were significant differences between Egyptian and Kenyan sites in prevalence and age distribution of S. mansoni-related hepatic fibrosis (36%vs. 3%, P < 0.001). Protocol image pattern scoring could be performed quickly and was stable to interobserver variation. However, there were unintended but systematic differences between study sites in the measurement of portal vein diameter (PVD) and wall thickness. By Niamey criteria, a high prevalence of portal dilation was scored for normal Egyptian subjects, which reduced the predictive value of image pattern for portal hypertension. Using alternative height-indexing of PVD, image pattern plus PVD findings predicted 15% of Egyptians and 2.5% of Kenyans were at risk for variceal bleeding, whereas locally derived PVD norms estimated 25% of Egyptians and 12% of Kenyans to be at possible risk. CONCLUSION: Niamey scoring criteria performed acceptably as a relative grading system for disease in schistosomiasis mansoni, but failed to account fully for site-to-site variation in test performance and morbidity prevalence. Consequently, standardized image pattern scoring appears to provide the most useful tool for detection and comparison of S. mansoni-associated morbidity in large-scale surveys.     

Comparison of an enzyme-linked immunosorbent assay using crude S. haematobium soluble egg antigen with a radioimmunoassay using purified S. mansoni egg antigen for the serodiagnosis of schistosomiasis haematobium

An enzyme-linked immunosorbent assay (ELISA) using crude Schistosoma haematobium soluble egg antigen (ShSEA) was compared with a radioimmunoassay (RIA) employing purified heterologous species S. mansoni egg antigen (MSA1) for the serodiagnosis of schistosomiasis haematobium in a group of 45 Nigerian school children living in an area endemic for S. haematobium. Both assay systems appeared applicable. The ELISA proved to be more sensitive detecting 100% of the 27 parasitologically positive individuals while the RIA defined 89% of this group. Neither test had false-positive results for the 10 non-endemic area parasitologically negative controls, although the ELISA demonstrated that 56% of the 18 endemic area parasitologically negative controls had anti-ShSEA antibodies. The RIA indicated that 44% of this group had anti-MSA1 antibodies. These latter findings were interpreted as related to the hyperendemicity of schistosomiasis haematobium for the study area.     

Intensity of Schistosoma mansoni, hepatitis B, age, and sex predict levels of hepatic periportal thickening/fibrosis (PPT/F): a large-scale community-based study in Ethiopia

To elucidate determinants of morbidity in schistosomiasis mansoni, a community-based study was undertaken involving 2,451 subjects (mean age, 18.8 +/- 15.3 [SD] years) from four endemic sites in Ethiopia. Overall prevalence of infection was 65.9%, reported blood in stools was 35.8%, and schistosomal periportal thickening/fibrosis (PPT/F) was 4.6%. Similarly, 43.2% were positive for at least one marker of hepatitis B virus (HBV), 5.3% were HBsAg positive, and 1.3% were anti-hepatitis C virus (HCV) positive. Prevalence of PPT/F increased significantly with increasing community prevalence and intensity of S. mansoni infection. In a multiple logistic regression analysis, intensity of egg excretion, markers of HBV infection, age, and male sex were significantly associated with PPT/F, whereas co-infection with other intestinal helminths was associated with lower odds for PPT/F. HCV was not associated with S. mansoni infection or with schistosomal PPT/F. In conclusion, integrated helminth control targeting school-aged children, who have the highest burden infection, should be used to substantially reduce the risk of periportal fibrosis.     

Liver involvement in human schistosomiasis mansoni. Regression of immunological and biochemical disease markers after specific treatment

Peripheral blood cholyglycine and procollagen-III-peptide were measured in 22 Zairean patients with hepatomegaly caused by S. mansoni before and after treatment with praziquantel. Circulating T-cell subsets and cutaneous in vivo delayed type hypersensitivity were assessed; serum neopterin and beta 2-microglobulin served as indicators for macrophage/lymphocyte activation. The results were compared to age and sex matched patients with S. mansoni infection limited to the intestinal tract and schistosomiasis free controls with equal socioeconomic background. Abnormal serum cholyglycine and neopterin levels and alterations of circulating T-cell subset frequencies were associated with hepatomegaly in schistosomiasis. Normalization of these parameters reflected a regression of egg-induced immunopathology as early as two months after specific chemotherapy. Serum procollagen-III-peptide concentrations rose significantly after treatment, suggesting release of propeptide previously incorporated without cleavage into tissue collagen. The combination of these biochemical and immunological parameters may allow assessment of the pathophysiological mechanisms responsible for liver disease in individual patients.     

洞庭湖渔民血吸虫病感染程度与免疫状态关系的研究

目的了解洞庭湖频繁接触疫水渔民的免疫状态及其与感染度和肝病变程度间的关系。 方法 采用询检、粪检、肝B超、流式细胞术（FCM）、免疫比浊法和ELISA法，检测血吸虫感染度、肝脾病变程度和血中CD4+和CD8+T细胞百分率及抗体水平等指标，用SPSS 10.0统计软件分析数据。 结果 与非疫区人群比较，疫区渔民人群外周血中的CD4+T细胞百分比和CD4＋/CD8＋细胞比值显著降低，而且粪检阳性患者均随血吸虫感染度增高和肝脾病变加重而更为突出。相反，疫区渔民血清总IgM抗体和特异性IgG水平增高，并随感染度增加或肝脾病变加重而更为明显。血清总IgA水平在肝脾病变严重的人群中有显著增高。总IgG水平仅粪检阳性者有增高现象。 结论 长期作业于洞庭湖的血吸虫感染渔民表现为细胞免疫功能降低而体液免疫亢进，这种免疫失调程度与其感染度和肝脾损害程度相关。     

Re-evaluation of schistosomiasis mansoni in Minas Gerais, Brazil. III. "Noroeste de Minas" mesoregion

This study was conducted to assess the presence of schistosomiasis mansoni in the "Noroeste de Minas" mesoregion, an area considered non-endemic. A malacologic survey and parasitologic stool examinations were undertaken in 13 municipalities of the mesoregion. A sample of 3,283 primary school students was submitted to fecal examination by the Kato-Katz method. A total of 3,627 planorbids was collected and examined. The molluscs were identified as Biomphalaria straminea in seven municipalities (Unaí, Bonfinópolis de Minas, Paracatu, Ja?o Pinheiro, Vazante, Lagamar and Lagoa Grande) and as Biomphalaria peregrina in one (Presidente Olegário). All planorbids were negative for Schistosoma mansoni. Four students were diagnosed with schistosomiasis in the municipalities of Buritis, Formoso, Paracatu and Unaí, but none of these cases was considered autochthonous. The data obtained indicate that the "Noroeste de Minas" mesoregion continues to be non-endemic for schistosomiasis mansoni, although the presence of intermediate hosts associated with parasitized individuals emphasizes the need for epidemiological surveillance of schistosomiasis in this mesoregion.     

Serological studies on schistosomiasis mansoni in the northeast Brazil (I)

Sera from the patients (N = 10) with schistosomiasis mansoni of the hospital of Federal University of Pernambuco, the Schistosoma mansoni egg-positive (N = 51) and -negative (N = 452) inhabitants in Cabo City area, out-patients (N = 37) of the IMIP hospital and Japanese immigrants (N = 127) in Petrolina City area of northeast Brazil as well as Japanese healthy subjects (N = 30) were examined by serological tests including an enzyme-linked immunosorbent assay with antigens prepared from eggs (ELISA-egg) and adult worms (ELISA-adult). The ELISA with egg or adult antigen correctly identified 100% of the uninfected individuals lived in non-endemic area of schistosomiasis. Moreover, when examined cross-reactivity of our ELISA with sera isolated from 78 subjects infected with various intestinal parasitic infections, only one of these sera reacted with the egg and adult antigens. On the examination of 51 sera from the egg-positive subjects, the ELISA-egg revealed the highest sensitivity (98.0%), whereas a large number of false negative reactions of ELISA-adult, Ouchterlony method using adult antigen, circumoval precipitation and immediate intradermal skin test were observed. A low sensitivity of these serologic tests except for ELISA-egg appears to be primarily due to their inability to detect antibody in the sera from egg-positive infantiles. There was no positive correlation between the absorbance values of these two types of ELISA among the sera isolated from ELISA-positive subjects. Rather, by the reactivity of these sera to egg or adult antigen, they could be divided into two subgroups; one reacted more positively with egg antigen and the other with adult antigen. Moreover, it was confirmed that the sera from young subjects (under 20 years old) appear to be highly reactive to the egg antigen than did aged ones. These data suggest that the ELISA with egg antigen, but not with the adult antigen, appears to be useful for the serological survey of schistosomiasis mansoni in the endemic area of northeast Brazil.     

Prevalence and distribution of schistosomiasis in Zimbabwe

Surveys for schistosomiasis of 14 619 eight- to ten-year-old children from 157 schools in Zimbabwe are reported. Zimbabwe is divided into three regions on the basis of differing prevalences of Schistosoma haematobium, with mean prevalence levels in each zone of 63.2, 37.1 and 14.3%. Two regions were identified for S. mansoni, with mean prevalence levels of 15.2 and 1.5%. In most regions Commercial Farming areas were shown to have higher levels of infection than Subsistence Farming areas. Females showed a significantly lower prevalence of infection with S. haematobium than males in all areas. Age prevalence surveys in support of the major survey showed the seven- to 20-year-old age group to contain 91.5% of the heavy infections with S. haematobium and 83.7% of the heavy infections with S. mansoni. The availability of surface water is recognized as the major factor governing the distribution and prevalence of schistosomiasis. Control of schistosomiasis is briefly discussed.     

Influence of the HLA-DQB1*0201 allele on the immune response in a Schistosoma mansoni infection

We previously reported the association of the major histocompatibility complex class II HLA-DQB1*0201 allele with hepatosplenic schistosomiasis. The aim of this study was to evaluate the cytokine responses of peripheral blood mononuclear cells (PBMCs) and the serum levels of immunoglobulin isotypes. The study population was selected from a schistosomiasis endemic area. No significant differences in cytokine profiles were detected in PBMCs stimulated with Schistosoma mansoni soluble egg antigen (SEA), regardless of the subjects DQB1*0201 genotype or infection status. However, previously infected DQB1*0201 positive individuals had significantly lower levels of IgG4 compared to DQB1*0201 negative individuals (P<0.05).     

Factors associated with Schistosoma mansoni infection 5 years after selective treatment in a low endemic area in Brazil.

Five years after a single dose treatment, prevalence, intensity and morbidity of schistosomiasis mansoni were evaluated in Agua Branca, a low endemic community in the South East Brazil (cure rate 94%). At community level, prevalence showed a decrease from 38.9 to 24.5% and the intensity of infection dropped from 119.5 to 38.9 eggs per g of faeces (epg). However, after the exclusion of immigrants, newborn children and individuals that had left the area after the first evaluation, the prevalence among the treated and followed population was not significantly affected. Multivariate analysis showed that the 10-29 age group and water contact for agricultural purposes were independently associated with the presence of infection on post treatment evaluation [OR 3.9 and 5.09, respectively]. A previous treatment among subjects older than 15 years was inversely associated [OR 0.58]. The authors wish to draw attention to the fact that mobility may lead to a serious bias in evaluating the impact of the control programme.     

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.     

Epidemiology of HIV and Schistosoma mansoni infections among sugar-estate residents in Ethiopia

Few studies have examined the interaction between schistosomiasis and infection with human immunodeficiency virus (HIV). The overlap between the two infections, and the effect of HIV infection on the egg output and worm load of individuals co-infected with Schistosoma mansoni, were therefore investigated in a sugar estate in central Ethiopia. The 1239 subjects were selected by stratified sampling of residents aged 15-54 years. The intensities of infection with S. mansoni were measured as egg output in stools (all subjects) and as the concentration of circulating cathodic antigen (CCA) in urine (a proxy for worm load, measured in 287 subjects). Schistosome infection was detected in 358 subjects [adjusted prevalence (AP) = 31.4%] and HIV infection in 52 (AP = 3.1%). The two infections clustered into different populations of the estate: the schistosome infections were predominantly found in the camps, and primarily affected young people (aged < 20 years) and those working in the field, whereas the HIV epidemic was found in the main village, primarily affecting those aged > 20 years and those who had recently arrived on the estate. Schistosome infection was detected in 348 of the 1187 HIV-negatives (AP = 31.6%) and 10 of the 52 HIV-positives (AP = 25.1%; P > 0.05). Schistosoma mansoni egg output was significantly lower in the HIV-positives than in the HIV-negatives (Mann-Whitney test; P = 0.03; ratio of geometric means = 0.74), and remained so after controlling for potential confounders (gender, age, and residence). However, CCA concentrations (i.e. worm loads) were found to be similar for these two groups, after controlling for potential confounders (age, gender, residence, and duration of residence).     

日本血吸虫与HBV感染协同致肝癌作用的研究

以血吸虫病流行地区和非流行地区常住居民1175人为对象，用ELISA法检测HBV、HCV血清学标志，用快速双抗体夹心ELISA检测抗体判断血吸虫感染。结果，流行地区感染率分别为：HBV（63．8％）、抗-HCV（2．2％），血吸虫（70．2％）；非流行地区感染率分别为HBV（49．7％），抗-HCV（0．9％），血吸虫（5．2％）。共检测490人血吸虫抗体，阳性176人（35．9％），阳性者HBV、HCV、肝硬变率显著高于阴性者。HBV、HCV，血吸中两种以上合并感染，均较单独感染对肝功能及肝硬变影响大，合并感染比上述感染阴性者的肝硬变患病率增长3．7－7．1倍，并发现HBV与血吸虫感染有相加致癌作用。     

Bacteriuria in urinary schistosomiasis in Egypt a prevalence survey.

An epidemiologic survey to assess the prevalence of bacteriuria in urinary schistosomiasis was carried out in a region endemic for urinary schistosomiasis in Egypt. Twenty of 390 (5.1%) school boys aged 5--16 years were bacteriuric. This prevalence rate is more than 10 times greater than that found in comparable surveys in areas non-endemic for urinary schistosomiasis. In this endemic population bacteriuria was found in 6.5% of active egg excreters and 2.3% of non-egg excreters.