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.     

Epidemiology of schistosomiasis mansoni in a low endemic area

We discuss the epidemiological patterns of schistosomiasis mansoni in areas with low transmission in Brazil. We define as areas of low endemicity those where the prevalence is less than 10%, the number Schistosoma mansoni eggs per gram of feces (epg) is less than 96, and carriers are asymptomatic. Data are from the county of Pedro de Toledo in the Ribeira Valley (S?o Paulo State) and were collected randomly according to the aggregate pattern of S. mansoni within the hosts. We suggest the replacement of parasitological methods by more sensitive and specific serological techniques. The main risk factor for infection is type of leisure activity. Infection is more frequent in the 10-14, 15-19, and 20-24-year age brackets. Geometric mean epg is 58.5. Intensity of infections correlates well (rs = 0.745) with prevalence. The highest index of potential contamination is in the 5-20-year age bracket (57.6%). Autochthonous cases show close association with Biomphalaria tenagophila, which has a low infection rate (2%). Prevalence, incidence, and intensity of infection patterns are similar to those of moderate and high endemic areas. Social and cultural aspects must be studied in order to obtain a global epidemiological view of schistosomiasis.     

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.     

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.     

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.     

Circulating antigens for assessing cure in schistosomiasis mansoni

An antigen capture enzyme-linked immunosorbent assay using antibodies made in rabbits and sheep to adult Schistosoma mansoni extract antigens has been developed and evaluated as a diagnostic test for schistosomiasis. 25 of 42 patients with S. mansoni infections had detectable circulating antigen while sera from all of 45 normal subjects and patients with other parasitic infections did not react. When the 25 with antigenaemia were retested 3 months after treatment, all 21 who were cured were negative while the 4 with persisting S. mansoni eggs in their stools remained positive. Antibodies to a fractionated egg antigen (CEF6) also diminished in most patients following successful treatment, but the reduction was insufficient to predict successful therapy.     

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

The signs and symptoms classically associated with Schistosoma mansoni infection were analysed in relation to their sensitivity, specificity and positive predictive value in identifying S. mansoni patients as well as more severe forms of the disease under field conditions. Data was collected in a survey conducted in a small urban area in the south east of Brazil (14.3% infection in the studied sample with a geometrical mean excretion of 95.5 S. mansoni eggs/gram of faeces). 'Blood in the stool' and a 'palpable and hardened liver' showed the highest positive predictive value; their presence, even in relatively low prevalence areas may be used by the health field workers as an indication of the existence of more advanced clinical forms of the disease.     

Stability of faecal egg excretion in Schistosoma mansoni infection

Stability of Schistosoma mansoni egg excretion was studied in 23 residents of a rural endemic area in North-east Brazil where the over-all prevalence rate was 87% and the peak geometric mean egg excretion was 308 eggs/ml (Bell method) in the 10 to 14-year-old age group. Stool examinations by the Kato method were performed for three to four consecutive days each month for three consecutive months. Both raw and transformed data showed significant stability of S. mansoni egg excretion from day to day and month to month in this population. A single Kato examination detected 68% of individuals who were excreting more than 400 eggs per gramme. Although S. mansoni egg excretion is stable over time, identifying individuals with high egg excretion in endemic populations requires sensitive quantitative methods.     

Geographical and socioeconomic factors relating to the distribution of Schistosoma mansoni infection in an urban area of north-east Brazil

A study was carried out in Santo Antonio de Jesus, a town in Bahia State, north-east Brazil, to determine the relationship between various biological, socioeconomic, behavioural, and geographical factors and the prevalence and intensity of Schistosoma mansoni infection. The town's population was around 45,000 and the study was targeted at all children born in 1970-71 who were living in the town at the time of the survey (August-November 1984). An extensive questionnaire was used to collect information on each child and on family and household conditions; samples of stools were also taken for examination (Kato-Katz method). A survey of water snails was also carried out and information on the distribution of their breeding sites was plotted on a map of the area. The overall prevalence of S. mansoni infection was 31.0%. Several variables that reflected different aspects of the population's way of life were strongly associated with the prevalence and the intensity of infection. Some of the findings are valuable for understanding the mechanisms involved in the occurrence of schistosomiasis and its distribution in urban locations as well as for defining high-risk groups, all of which are important for planning control strategies.     

Epidemiology and morbidity of Schistosoma mansoni infection in a fishing community along Lake Albert in Uganda

Schistosoma mansoni infection, associated morbidity and symptoms were studied in Piida fishing community at Butiaba, along Lake Albert, Uganda, from November 1996 to January 1997. The study revealed that S. mansoni is highly endemic with an overall prevalence of 72%, a mean intensity of 419.4 eggs per gram (epg) faeces (geometric mean for positives only), with 37.8% of males and 33.0% of females excreting over 1000 epg. Prevalence and intensity peaked in the 10-14 year old age group and decreased with increasing age. Females were less heavily infected than males. Differences were also shown between tribes. Diarrhoea and abdominal pain were commonly reported in Piida. However, no clear-cut correlation between intensity of S. mansoni infection and these conditions could be demonstrated, indicating that retrospective questionnaires concerning S. mansoni related-symptomatology are of limited value. Organomegaly, as assessed by ultrasonography, was frequent and hepatomegaly was associated with heavy S. mansoni infection. No correlation was demonstrated between splenomegaly and infection. This study emphasizes that schistosomiasis mansoni is a major public health problem in Piida fishing community and presumably also in many similar fishing communities. These observations call for immediate intervention and can help in planning long-term strategies for sustainable morbidity control.     

Biology of Biomphalaria occidentalis Paraense, 1981 and Biomphalaria tenagophila (d'Orbigny, 1835), in laboratory conditions]

Specimens of Biomphalaria occidentialis and Biomphalaria tenagophila were reared in S. Paulo, Brazil under laboratory conditions, with a view to know their biological characteristics. Oviposition and eggs/oviposition ratio were recorded over twelve months so as to obtain information on the number of egg-masses per animal and the number of eggs per egg-mass, as also the number of hatched eggs per egg-mass for each period of 30 days, i.e., the hatching-rate per period. The incubation period was about the same for both species, but the oviposition and egg oviposition ratio were greater in B. tenagophila.     

Egg count variability and sensitivity of a thin smear technique for the diagnosis of Schistosoma mansoni

Variation in daily egg counts, and in counts for samples of the same stool, was investigated in children with Schistosoma mansoni and Ascaris lumbricoides infections, using a thin smear technique. The results indicated that counts vary according to the stool consistency; drier stools from the same person producing up to seven times greater counts than wet ones. The sensitivity of the technique was tested in schoolchildren living in an endemic S. mansoni area, and found to detect all infections with intensities of greater than 50 eggs per gram of stool, after examination of only one slide containing 40mg stool. The sensitivity varied with the intensity of infection. The relevance of these findings to diagnosis in field situations is discussed.     

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.     

Evaluation of enzyme linked immunosorbent assay (ELISA) as a diagnostic tool for schistosomiasis

The sensitivity and specificity of the ELISA were assessed in the diagnosis of schistosomiasis in two groups of school children, one attending a rural school where schistosomiasis is highly prevalent, the other attending a school in an urban locality where schistosomiasis is absent. The results showed that the ELISA had a sensitivity of 92.2% and 100% in Schistosoma mansoni and mixed infection, respectively. The specificity of the test increased from 92.1% to 98% when a fourth stool examination was done in cases giving false positive results. ELISA positively was significantly increased with the increase in egg count till it reached 100% in cases with 160 eggs per gram stools.     

Schistosomiasis: new occurrence of Biomphalaria straminea in Belo Horizonte, Minas Gerais

In Belo Horizonte, Minas Gerais, Brazil, the snail Biomphalaria straminea was found in the Pampulha region. Recently the snail was found in ditches in the old Santa Lúcia Reservoir, a now-extinct focus of schistosomiasis transmission by B. glabrata. The snails were collected and examined to verify whether they were naturally infected with Schistosoma mansoni. Negative specimens were used for breeding or infection with the LE strain of S. mansoni from the laboratory and another strain obtained from eggs found in the feces of a schoolchild (VGS) from Belo Horizonte. Among the 1890 snails collected from 1994 to 1995, none were infected with S. mansoni. Among 87 snails collected and exposed to the LE strain, 9 (10.3%) shed cercariae; among 83 snails from F1, and exposed to LE, 10 (12.0%) shed cercariae. Among 88 snails exposed to VGS, 10 (11.3%) shed cercariae. In Belo Horizonte, schistosomiasis is transmitted by B. glabrata and B. tenagophila. However, currently there exists the risk of appearance of a focus in which B. straminea could be the host if prophylactic measures are not taken by the authorities responsible for the construction of a park and lake at that site.     

Occurrence of schistosomiasis mansoni vectors on the Northern coast of the State of São Paulo, Brazil

This article comments on the detection of Biomphalaria tenagophila (d'Orbigny, 1835) infected with Schistosoma mansoni Sambon, 1907 in Caraguatatuba and the introduction of Biomphalaria straminea (Dunker, 1848) in Ilha Bela, two municipalities on the Northern coast of the State of S?o Paulo, Brazil. Infected snails were collected from a ditch located in the Olaria district. B. straminea and B. tenagophila were living in syntopy in a stream situated in Barra Velha. Such epidemiological findings indicate the risk of spread of schistosomiasis mansoni in the region, a consequence of inadequate basic sanitation.     

Pattern of water contact activities in relation to S. mansoni infection in rural area in Giza Governorate, Egypt

Schistosomiasis is associated with human behavior in relation to water. Study of different patterns of water contact activities would help in planning strategies for control. This study aims to describe patterns of water contact activities in relation to S. mansoni infection in El-Shobak El-Sharki village in Giza governorate, in Egypt. A sample of 695 households was taken from about 127 houses. They provided stools samples and a water contact questionnaire for different activities, regions, sites, time of the day, duration of activities, patterns in different age and sex groups. Univariate and multivariate analysis of data was done. It was found that, adult males had the highest prevalence rate, then adult females while children had the least (33.5%, 27.5% and 17.4% respectively, p-value < 0.0001). Infection rate is higher in those having water contact activities, with Odds Ratio (OR) 2.01 and 95% Confidence Intervals (CI) (.94-4.24). Other significant factors are, the site of activities, time of the day and duration of contact, with p-value < 0.05. The highest score for the different patterns of activities in adult males are mainly occupational as agriculture and irrigation, their OR (95% CI) are 2.82 (.91-5.94) and 2.58 (.89-5.41), respectively. As regards females, the highest score is for domestic daily activities as washing infant clothes and utensils, their OR (95% CI) is 2.19 (.91-4.73) and 1.83 (.80-4.16) respectively. Children have the least score, their activities is mainly recreational as swimming, OR (95% CI) is 1.77 (.79-4.02). Multiple logistic regression analysis revealed that, male's activities and their longer duration are highly significant factors with prevalence as the dependant variable, OR (95% CI) is 3.07 (.73-8.19) for activities, and is 3.67 (.31-9.38) for duration. It is concluded that, human exposure pattern, in general, favors the transmission of S. mansoni. Prevalence of infection coincides with water contact activities in different age, sex and farming occupation. So, the control of S. mansoni in Egypt is not a pure medical affair. It needs multidisciplinary upgrading actions to be taken in different sectors of agriculture and irrigation reform in Egypt.     

Influence of vitamin A on the immune response of Schistosoma mansoni-infected rats

Nutritional (vitamin A levels, weights), parasitological (adult worm burden, count of eggs in liver, stool examination) and immunological (IgE serum levels, anti-Schistosoma mansoni antibodies, lymphocyte stimulation by concanavalin A and S. mansoni antigenic extract) parameters were studied in three groups of rats, a non-infected and normally fed control group, a S. mansoni-infected but normally fed group, and a S. mansoni-infected group with experimentally induced vitamin A deficiency. The number of worms was found significantly higher in the third (53 +/- 19) than in the second group (2 +/- 2) (p less than 0.001). There were many eggs in the liver surrounded by granulomatous reactions in the third group (399 +/- 73 epg liver). All stool examinations were negative. IgE levels and anti-S. mansoni antibody titres were significantly lower (p less than 0.001) in the third than in the second group. The concanavalin A lymphocyte stimulation indexes did not differ significantly between groups 2 and 3; the S. mansoni lymphocyte stimulation index was only significantly positive in group 3 (p less than 0.001). These results indicate a decrease in the humoral immune response without alteration of cellular immune response in vitamin A-deficient rats infected with S. mansoni.     

Human Opisthorchis and Haplorchis infections in Laos.

A study of the epidemiology of trematode infections was carried out in Vientiane province, Laos, comprising examination of snails, fish, cats, and human stools. Opisthorchis viverrini cercariae were found in the snail Bithynia siamensis goniomphalus (Bithyniidae) and Haplorchis taichui cercariae in Tarebia granifera (Thiaridae). O. viverrini metacercariae were recorded in the flesh of 7 species of cyprinid fish; metacercariae of the heterophyid fluke Haplorchis taichui were found in 4 species of cyprinid fish and those of H. pumilio in 2 species. Cats from the same localities were infected with O. viverrini and 4 species of heterophyid flukes, frequently as multiple infections. The highest prevalence of small fluke eggs in human stools was recorded in the 20-29 years age group, particularly in males (90.4%). Three-quarters of human infections were light (less than 1000 eggs/g), the highest value (2975 eggs/g) being recorded in the 10-14 years age group. Identification of small flukes excreted by Laotian patients after treatment with praziquantel in Czechoslovakia revealed more cases with H. taichui than with O. viverrini. The results confirmed the simultaneous occurrence of O. viverrini and intestinal heterophyid flukes in the area studied.     

Schistosoma mansoni in pregnancy and associations with anaemia in northwest Tanzania

Schistosomiasis among pregnant women has been inadequately investigated. In order to determine the importance of Schistosoma mansoni in this subgroup, we conducted a cross-sectional survey of 972 women in Tanzania and investigated the prevalence of Schistosoma mansoni, hookworm and malaria and their associations with anaemia. Overall, 63.5% of women were infected with S. mansoni, with prevalence highest among younger women and decreasing with increasing age. The prevalence of hookworm was 56.3%, and 16.4% of women had malaria parasitaemia. Overall, 66.4% of women were anaemic. Increased risk of anaemia was associated with heavy infection with S. mansoni but not hookworm or Plasmodium falciparum parasitaemia.