Sonographic studies of schoolchildren in a village endemic for Schistosoma mansoni

Parasitological, clinical, and sonographic examinations were performed on 309 school children in a village endemic for schistosomiasis mansoni. Data from the 255 denying treatment within the previous 2 years were analysed separately. On a single Kato examination 42% were uninfected; the remainder had light (26%), moderate (21%), or heavy (11%) infections with Schistosoma mansoni. Hepatomegaly (53%) and palpable spleens (35%) were common but clinical and parasitological findings often were unrelated. Abdominal sonography also demonstrated a high frequency of hepatomegaly (82%) and splenomegaly (49%). Sonographically determined liver span and spleen size correlated with the egg count. Sonographic lesions of periportal fibrosis of schistosomiasis mansoni with thickening of portal tracts and portal vein walls were frequently present and more common in infected than in uninfected children, and were correlated with the number of S. mansoni ova in the stool. Ultrasonographically detected periportal fibrosis was a reliable measurement of the prevalence and morbidity of schistosomiasis mansoni in this population, and provided very useful information, even when the parasitological and clinical findings were equivocal.     

Rapid screening for Schistosoma mansoni in western Côte d'Ivoire using a simple school questionnaire

The distribution of schistosomiasis is focal, so if the resources available for control are to be used most effectively, they need to be directed towards the individuals and/or communities at highest risk of morbidity from schistosomiasis. Rapid and inexpensive ways of doing this are needed, such as simple school questionnaires. The present study used such questionnaires in an area of western Côte d''Ivoire where Schistosoma mansoni is endemic; correctly completed questionnaires were returned from 121 out of 134 schools (90.3%), with 12,227 children interviewed individually. The presence of S. mansoni was verified by microscopic examination in 60 randomly selected schools, where 5047 schoolchildren provided two consecutive stool samples for Kato-Katz thick smears. For all samples it was found that 54.4% of individuals were infected with S. mansoni. Moreover, individuals infected with S. mansoni reported "bloody diarrhoea", "blood in stools" and "schistosomiasis" significantly more often than uninfected children. At the school level, Spearman rank correlation analysis showed that the prevalence of S. mansoni significantly correlated with the prevalence of reported bloody diarrhoea (P = 0.002), reported blood in stools (P = 0.014) and reported schistosomiasis (P = 0.011). Reported bloody diarrhoea and reported blood in stools had the best diagnostic performance (sensitivity: 88.2%, specificity: 57.7%, positive predictive value: 73.2%, negative predictive value: 78.9%). The study, which is probably the largest of its kind ever undertaken in Africa, revealed a moderate diagnostic performance of questionnaires for identifying individuals and/or communities at high risk from S. mansoni.     

Changes in human schistosomiasis levels after the construction of two large hydroelectric dams in central C?te d'Ivoire.

The construction of large dams has been shown to increase the prevalence and intensity of human schistosomiasis. However, until now no study had been carried out to assess the impact of such a project in Côte d''Ivoire. For Kossou and Taabo, two large dams which became operational in the 1970s, baseline data are available on schistosomiasis prevalence in the surrounding area before dam construction, so that the changes in schistosomiasis levels can be assessed. We re-evaluated the prevalence of Schistosoma haematobium and S. mansoni in November 1992, by analysing 548 urine and 255 stool samples, respectively, from schoolchildren from five villages around each lake. A marked increase in the overall prevalence of S. haematobium was observed, from 14% to 53% around Lake Kossou and from 0 to 73% around Lake Taabo. Baseline data for S. mansoni are only available for Lake Taabo, where a prevalence of 3% was found in 1979 and where the prevalence in 1992 was still low at 2%. The construction of these two large dams therefore led to little change in S. mansoni prevalence but to a significant increase in that of S. haematobium.     

Studies on schistosomiasis in the Niger Delta: Schistosoma intercalatum in the urban city of Port Harcourt, Nigeria

Ova of S. intercalatum have been found in the urban city of Port Harcourt in the Niger Delta area of Nigeria, following examination of stool and urine samples from 1,709 persons (5-15 years of age) resident in various parts of the city. The ova occurred only in urine, with prevalence ranging from 1.0% to 9.8% with an overall prevalence of 5.7%. The intensity of the infection was low. Most infected individuals had counts of less than 500 ova in total bladder content. There was no significant difference in either the prevalence or intensity of the infection among the sexes (Male; prevalence 6.1%, intensity 527.3 vs Female; prevalence 5.4%, intensity 500.9). No case of infection with either S. haematobium or S. mansoni was encountered in the study. Malacological surveys in the gutters, creeks, streams and stagnant waterbodies within the city showed the presence of Lymnaea natalensis, Bulinus forskalii, Pila ovata, Melanoides tuberculata, Physa sp., Lanistes ovum and Segmentorbis sp. B. forskalii is indicated as the probable vector of S. intercalatum in the city. The growing problem of urban schistosomiasis in tropical Africa is discussed. Further studies on urban transmission and epidemiology of schistosomiasis in the Niger Delta area of Nigeria is also indicated.     

Multiplex real-time PCR for the detection and quantification of Schistosoma mansoni and S. haematobium infection in stool samples collected in northern Senegal

A multiplex real-time PCR assay for the detection and quantification of Schistosoma mansoni and S. haematobium DNA in faecal samples was developed and evaluated as an alternative diagnostic method to study the epidemiology of schistosomiasis. Primers and probes targeting the cytochrome c oxidase gene were designed for species-specific amplification and were combined with an internal control. Using positive control DNA extracted from adult Schistosoma worms and negative control samples (n=150) with DNA from a wide range of intestinal microorganisms, the method proved to be sensitive and 100% specific. For further evaluation, duplicate stool specimens with varying S. mansoni egg loads were collected in northern Senegal from pre-selected individuals (n=88). The PCR cycle threshold values, reflecting parasite-specific DNA loads in faeces, showed significant correlation with microscopic egg counts both for S. mansoni in stool and S. haematobium in urine. The Schistosoma detection rate of PCR (84.1%) was similar to that of microscopy performed on duplicate stool samples (79.5%). The simple faecal sample collection procedure and the high throughput potential of the multiplex real-time PCR provide a powerful diagnostic tool for epidemiological studies on schistosomiasis in remote areas, with possibilities for extension to other helminths or protozoa using additional molecular targets.     

Status of Schistosoma Mansoni Prevalence and Intensity of Infection in Geographically Apart Endemic Localities of Ethiopia: A Comparison

Background

Schistosomiasis is one of the chronic and neglected tropical diseases affecting rural communities. Heavy infections contribute to anemia and can retard children''s growth, physical activity and cognitive function. This study was conducted in order to determine the prevalence, intensity and variation of Schistosoma mansoni infection among human subjects in geographically apart localities. The prevalence and intensity of Schistosoma mansoni infection was assessed in three geographically apart endemic areas of Ethiopia from May to August 2010 through cross-sectional approach.

Methods

A total of 1073 individuals (528 males and 545 females) were found eligible for the study. Their age ranged from 5–60 years with mean age of 11 years in Wondo Genet, 22 years in Kemissie and 24 years in Sille-Elgo. Small plastic sheets were distributed to the study participants and sizable stool specimens were collected and examined using Kato-Katz method (41.7mg template).

Result

The prevalence of Schistosoma mansoni infection among the study participants in Kemissie, Wondo Genet and Sille-Elgo was 89.6%, 59.9%, and 31.6%, respectively. The highest geometric mean of egg per gram of stool for Kemissie, Wondo Genet and Sille-Elgo was, 5208 and 346, 8472 and 252, 3960 and 91, respectively.

Conclusion

It was observed that there was comparable variation in the prevalence and intensity of infection among the study localities. Moreover, it is indicated that S. mansoni is still an ongoing public health problem which requires integrated intervention activities in the country.     

Efficacy and side effects of praziquantel against Schistosoma mansoni in a community of western Côte d'Ivoire

Praziquantel is efficacious against the adult stages of all human schistosome parasites, and has become the drug of choice for morbidity control of schistosomiasis. There is concern that resistance to praziquantel might develop or already exists, and could be further facilitated through new control initiatives relying on large-scale administration of praziquantel. Therefore, monitoring praziquantel efficacy in different epidemiological settings is required. We assessed the efficacy and side effects of praziquantel against Schistosoma mansoni in a rural community of western C?te d'Ivoire. Three consecutive stool specimens from 545 children and adults were examined by the Kato-Katz technique, revealing an overall prevalence of 40.9%. S. mansoni-infected individuals were treated with a single oral dose of praziquantel at 40 mg/kg. The most frequent side effects were abdominal pain, dizziness and diarrhoea. The overall cure rate, assessed 6 weeks post-treatment, was 60.9%. Moderate or heavy infections were only cleared in half or one-third of the individuals, respectively. The total egg count reduction was 61.4%. Infection intensity pre-treatment was significantly associated with age, cure rate, reported diarrhoea and dizziness. Our findings call for additional studies that rigorously evaluate the efficacy of praziquantel against different schistosome species in entire communities, using similarly sensitive diagnostic approaches as employed here.     

Fibre-optic sigmoidoscopy compared with the Kato technique in diagnosis and evaluation of the intensity of Schistosoma mansoni infection.

450 patients in Riyadh, Saudi Arabia, complaining of chronic abdominal pain and, coming from different countries endemic for schistosomiasis, were examined endoscopically using fibre-optic colono- or sigmoidoscopes, and rectal biopsies were examined for Schistosoma mansoni ova. After a preliminary study showed that more than 6 biopsies did not increase the positivity rate, 6 biopsies were taken from the rectum and examined by transparency technique. 280 were positive for S. mansoni, 9 of them having in addition S. haematobium. 4 patients had polyps in the sigmoid colon and rectum. When these positive cases were examined using duplicate 50 mg Kato smears, only 160 (57.1%) were positive. There was a highly positive correlation between the intensity of infection as graded by the 2 techniques. We recommend examination of 6 rectal biopsies using fibre-optic sigmoidoscopy when available in small communities with a patchy distribution of schistosomiasis like Saudi Arabia. The method could also be used to exclude schistosomiasis in persons who have moved from rural to urban or non-endemic areas and are unlikely to be re-exposed to infection.     

Spontaneous reduction in Schistosoma mansoni infection in endemic communities of the lake Tana basin, north-western Ethiopia

The prevalence and intensity of Schistosoma mansoni infections were studied in 3 endemic communities in north-western Ethiopia using the Kato-Katz stool examination technique to determine changes in the epidemiology of schistosomiasis in the absence of control programmes. The prevalence declined in Chwahit community by 21.6%, and in the villages of Jenda and Guramba by 43.2 and 100% respectively in the course of 15 years. This spontaneous reduction in schistosomiasis is perhaps the result of recurrent drought in the area. This finding has implications for public health programmes in the area and intervention measures against schistosomiasis.     

Are there interactions between schistosomes and intestinal nematodes?

A survey for intestinal parasites was carried out in a homogenous rice cultivation area, in which people had equal opportunities of acquiring the local endemic helminthiases, including schistosomiasis mansoni. The numbers of Schistosoma mansoni eggs excreted in faeces were counted. Infections with S. mansoni, Ascaris lumbricoides, ancylostomes and Trichuris trichiura were not randomly distributed, but were correlated, depending on the species of worms present. The S. mansoni egg counts were positively correlated with ancylostome infection but inversely correlated with A. lumbricoides and T. trichiura. Patients with schistosomiasis associated with 2 other helminth infections excreted more S. mansoni eggs than the patients with S. mansoni plus only one other helminth infection.     

Preliminary evaluation of morbidity due to S. haematobium and S. mansoni in the area of the future Adjarala Dam in Benin

The aim of this study was to provide a preliminary assessment of morbidity due to schistosomiasis in the area of the future Adjarala Dam in Benin. We included 412 schoolchildren from five villages in the study. The mean age of the children was 9.4 +/- 2.3 years and the sex ratio (F/M) was 0.94. These children underwent parasitological examination. The children provided urine samples, which were examined by eye, filtered and tested for blood and protein. Stool samples were examined using Kato's technique and an ultrasound scan of the urinary tract was performed. We carried out a survey of snails at the possible transmission sites of all the villages, with a view to identifying the intermediate hosts. We detected S. mansoni and S. haematobium in the area. Urinary schistosomiasis was mesoendemic (prevalence of 19.7%) whereas schistosomiasis due to S. mansoni was hypoendemic (prevalence of 3. 9%). Ultrasound scans showed that 28% of the children had bladder lesions and that 2.5% were carriers of hydronephrosis. We compared the diagnostic performances of the various indirect indicators of morbidity. We found that a history of hematuria was the most sensitive indicator (88%) but that the sensitivity of this indicator differed significantly according to the sex of the child. Hematuria >= 1+ was the most effective indicator. Snail surveys showed that Biomphalaria pfeifferi and Bulinus globosus were present in the area.     

Assessment of the age-specific disability weight of chronic schistosomiasis japonica

OBJECTIVE: To estimate the age-specific disability weight of chronic schistosomiasis japonica in China. METHODS: Between October 2004 and January 2005, residents from two schistosome-endemic counties were screened for Schistosoma japonicum infection using an enzyme-linked immunosorbent assay. Disability and morbidity were assessed in seropositive individuals using the European quality of life questionnaire with an additional cognitive dimension (known as the "EQ-5D plus") and ultrasonography. The age-specific disability weight of chronic schistosomiasis was estimated based on participants self-rated health scores on the visual analogue scale of the questionnaire; the relationships between health status, morbidity and disability weight were explored using multilevel regression models. FINDINGS: Of 2843 seropositive individuals, 1419 (49.9%) were classified as having chronic schistosomiasis. Hepatomegaly was found in 76.3% (1082/1419); hepatic fibrosis was found in 73.3% (1040/1419); and splenomegaly was found in 18.6% (264/1419). Diarrhoea was the most common self-reported symptom (46.0%; 653/1419), followed by abdominal pain (32.6%; 463/1419), impaired capacity to work or study (30.7%; 436/1419), and blood in the stool (11.1%; 157/1419). More than half of the respondents reported impairments in at least one dimension of the EQ-5D plus questionnaire, particularly pain or discomfort (47.9%; 675/1410) and anxiety or depression (39.4%; 555/1410). The overall disability weight was 0.191, and age-specific weights ranged from 0.095 among those aged 5-14 years to 0.246 among those aged > 60 years. Multilevel regression models indicated that the disability weight was significantly associated with the participants sex, grade of hepatic fibrosis, the presence of hepatomegaly, abdominal pain, blood in the stool, impaired capacity to work or study, and cognition. CONCLUSION: The disability weight attributable to chronic schistosomiasis japonica is high and increases with age. Our findings call for a reappraisal of the disability weights due to chronic schistosomiasis mansoni and schistosomiasis haematobia as well as a re-estimation of the global burden of schistosomiasis.     

Prevalence of renal involvement in Schistosoma japonicum infection

244 outpatients and 100 hospitalized patients with confirmed Schistosoma japonicum infection were prospectively surveyed for the presence of nephropathy. There was no association between schistosomiasis and renal disease in the outpatient group. Three hospitalized patients had evidence of significant nephropathy, but this number was not significantly higher than in a control group of 100 hospitalized age and sex-matched control patients without schistosomiasis. One schistosomiasis patient with severe nephrotic syndrome underwent percutaneous renal biopsy. Neither S. japonicum antigen nor antibody was found in the biopsy specimen. 64 of the 100 hospitalized patients had portal hypertension; in 28 patients there was hepatic decompensation. Only one of these hepatosplenic patients had evidence of renal disease. Thus renal involvement was uncommon in patients presenting various manifestations of chronic S. japonicum infection, including those with severe hepatosplenic disease. These results contrast markedly with S. mansoni infection, in which nephropathy associated with advanced liver disease is a distinct, well-recognized clinical entity.     

Current status of S. mansoni infection in El-Prince village, Alexandria Governorate

The present work was implemented to determine the current status of Schistosoma mansoni infection in "El-Prince" village, near Alexandria, which was studied before as a control village between 1985 and 1990. Stool examination was performed on 571 of the inhabitants by Kato thick smear technique and intensity of infection was determined. Prevalence was found to be 15.4% with a percentage decrease of 53% from the 1990 survey. The geometric mean egg count (GMEC) ranged from 19.05 eggs/gram of stools in children aged five years or less to 81.86 in the oldest group greater than 50 years of age and averaged 42.26. Age stratified prevalence of infection peaked at 31.4% in the (20 to 25)-year-old age group. High prevalence of 23.6% was also observed in the age group from 36 to 50 years. Infection in males was higher than females (17.8% vs.13.5%). However the difference was not statistically significant (chi2 = 2.2, P = 0.0086). Risk factors significantly associated with the infection were an age more than 5 years, male gender, males with water contact activities and having done a previous laboratory analysis for schistosomiasis. The community category of the village changed from high prevalence in 1990 to moderate prevalence in 2002. Most of the infected individuals (85%) had light intensity of infection (less than 99 eggs /g stools). Active screening and treatment programs should be maintained in the area. More control measures should be directed towards older people who should be included in evaluation of control programs.     

Serodiagnosis of human Schistosoma mansoni infections: enhanced sensitivity and specificity in ELISA using a fraction containing S. mansoni egg antigens omega 1 and alpha 1

Six fractions of Schistosoma mansoni egg homogenate obtained by cation exchange chromatography were tested in an enzyme-linked immunosorbent assay (ELISA) for their efficacy in serodiagnosis of human S. mansoni infections. One cationic fraction (CEF6) containing egg antigens omega 1 and alpha 1, was found to be highly reactive with a S. mansoni positive reference serum pool. 94 of 95 sera from individuals infected with S. mansoni gave a positive reaction with CEF6, and no cross reactivity was obtained with this antigenic fraction and sera from donors infected with heterologous non-schistosome parasites and cases of avian cercarial dermatitis. Only 10 of 165 sera from patients with S. haematobium and three of 10 sera from patients with S. japonicum were positive with S. mansoni egg CEF6. In one group of patients from West Africa, examined both serologically and parasitologically at a six-monthly interval, the measurement of antibody to CEF6 provided a more sensitive diagnostic aid than stool examination.     

Field-based evaluation of a reagent strip test for diagnosis of Schistosoma mansoni by detecting circulating cathodic antigen in urine before and after chemotherapy

The sensitivity of a reagent strip test for the diagnosis of schistosomiasis by detecting circulating cathodic antigen (CCA) in urine was evaluated under field conditions using 251 stool and urine samples collected from a Schistosoma mansoni-endemic area of Ethiopia. The specificity of the test was evaluated in an area where schistosomiasis is not endemic. Stool samples were examined microscopically using duplicate Kato slides and formol-ether concentration methods. The effectiveness of the test in monitoring efficacy was also evaluated following chemotherapy. The results revealed that detection of CCA in urine using the one-step reagent strip test was superior to the stool examination methods (P<0.05) in indicating the prevalence of the disease. Assuming the combination of parasitological test results as the gold standard, the sensitivity and specificity of the test were 82.1% and 75.9%, respectively. The results of egg counts suggested the potential use of urine CCA in indicating the intensity of infection as an alternative to parasitological methods. The sensitivity and specificity of the test were 75% and 73.7%, respectively, following chemotherapy. Diagnosis of S. mansoni infection in urine using reagent strips would provide information on the prevalence of the disease, although further study is needed to improve its sensitivity and specificity.     

Human intestinal schistosomiasis in communities living near three rivers of jimma town, South Western ethiopia

Background

Schistosoma mansoni is one of the parasites with high public and medical importance in Ethiopia. However, information is scarce about S. mansoni epidemiology in people living with higher risk of infection in Jimma town. This study was designed to determine point prevalence, intensity and risk factors of S. mansoni infection among residents nearby three rivers of Jimma town and assess the rate of Biomphalaria species shading cercariae from January to April, 2007.

Methods

A cross-sectional study was conducted in communities residing nearby three rivers of Jimma town. Structured questionnaires were used to collect data on socio- demographic and behavioral risk factors. After physical examination, stool samples were collected from 517 study participants and processed with Kato-Katz technique for microscopic examination and quantification of egg load. Snails were collected for identification of Biomphalaria species and then checked for cercarial shading.

Results

The prevalence of S. mansoni was 26.3 % with intensity ranging 24 to 936 eggs per gram of stool. Participants in the age group 10–19 years, OR = 2.19 (95% CI; 1.10 – 4.34), and those living near the Awetu River, OR = 2.67 (95% CI; 1.06 – 6.75), had higher risk of S. mansoni infection. Moreover, water contact while crossing a river, OR = 3.77 (95% CI; 1.79 – 7.95), and swimming, OR = 2.59 (95% CI; 1.37 – 4.91, was significantly associated with infection. Biomphalaria snails collected from Chore and Awetu Rivers shaded higher rate of cercariae compared with Kito River.

Conclusion

A moderate prevalence of S. mansoni infection was shown in the study population. Infection rate among the residents correlated with rate of cercarial shading Biomphalaria snails. Treatment of targeted groups, appropriate health education and environmental measures (e.g. snail control) are needed to improve the situation.     

Notes on the use of urine-CCA dipsticks for detection of intestinal schistosomiasis in preschool children

Urine-dipstick diagnostic tests that detect schistosome circulating cathodic antigen (CCA) have the potential to provide more sensitive and rapid testing for intestinal schistosomiasis in field-based surveys; this is especially so when examining preschool children, from whom it may be difficult to obtain consecutive stool samples. To assess the performance of urine dipsticks, 569 preschool children from four villages along the shore of Lake Albert, Uganda, were screened for Schistosoma mansoni by Kato-Katz (K-K) examination of a single stool sample and CCA urine dipsticks. The prevalence of infection was 32.2% by K-K and 40.0% by CCA tests. Sensitivity and specificity were influenced by whether 'trace' results from the CCA test were characterised as positive or negative for infection with S. mansoni; ambiguities around this issue need to be resolved. Nevertheless, the CCA test showed particular promise for routine epidemiological screening in this setting.     

The role of hygienic bathing after defecation in the transmission of Schistosoma mansoni

Transmission of Schistosoma mansoni depends on fecal eggs reaching water, but the way this happens is poorly understood. We studied the role of hygienic bathing after defecation in the contamination of water with S. mansoni eggs. Individuals in an endemic community in Northern Senegal (n=991) were examined for S. mansoni infection and a random sample (22%) was interviewed about stool disposal practices and hygienic behavior. We assessed the presence and viability of S. mansoni eggs adhering to the peri-anal region of 13 infected volunteers, by counting the miracidia in the water they had used for hygienic washing; for 10 of them (77%) miracidia were demonstrated. From the population infection distribution, average number of defecations per day, proportion of individuals bathing after defecation, and association between miracidial counts and infection intensity, we calculated a daily population miracidial output of approximately 30,000 through hygienic bathing. For comparison, one complete stool reaching the water was calculated to yield approximately 2500 miracidia. Thus, 12 individuals in this population should defecate into the water every day to produce the same number of miracidia as through hygienic bathing. Our results suggest a major role of hygienic bathing after defecation in the transmission of S. mansoni.     

Efficacy of oxamniquine and praziquantel in the treatment of Schistosoma mansoni infection: a controlled trial

OBJECTIVE: To evaluate the therapeutic efficacy of oxamniquine and praziquantel, the two most clinically important schistosomicide drugs, and to compare the accuracy of faecal examination with the accuracy of oogram in testing for Schistosoma mansoni infection. METHODS: In a triple-masked and randomized controlled trial, 106 patients infected with S. mansoni were randomly allocated to one of three statistically homogeneous groups. One group was given 60 mg/kg praziquantel per day for three consecutive days, another was given two daily doses of 10 mg/kg oxamniquine, and the placebo group received starch. Faecal examinations (days 15, 30, 60, 90, 120, 150, and 180 after treatment) and biopsy of rectal mucosa by quantitative oogram (days 30, 60, 120, and 180) were used for the initial diagnosis and for evaluating the degree of cure. The chi2 test and the Kruskal-Wallis test were used to compare variables in the three groups. Survival analysis (Kaplan-Meier) and the log-rank test were used to evaluate the efficacy of the treatments. FINDINGS: The sensitivity of stool examinations ranged from 88.9% to 94.4% when patients presented with >5000 S. mansoni eggs per gram of tissue (oogram); when the number of eggs dropped to <1000 eggs per gram, sensitivity was reduced (range, 22.7-34.0%). When cure was evaluated by stool examination, oxamniquine and praziquantel had cure rates of 90.3% and 100%, respectively. However, when the oogram was used as an indicator of sensitivity, the oxamniquine cure rate dropped dramatically (to 42.4%), whereas the rate for praziquantel remained high, at 96.1%. CONCLUSIONS: Praziquantel was significantly more effective than oxamniquine in treating S. mansoni infection. The oogram was markedly more sensitive than stool examinations in detecting S. mansoni eggs and should be recommended for use in clinical trials with schistosomicides.