Efficacy of Praziquantel Treatment and Schistosoma Mansoni Infection among Primary School Children in Kemisse Town,Northeast Ethiopia

BackgroundSchistosoma mansoni infection is endemic in Ethiopia. The epidemiology of S. mansoni and the efficacy of praziquantel among schoolchildren have not been well documented in different parts of the country including our study area. Therefore, this study aimed to determine the status of S. mansoni infection and evaluate the therapeutic efficacy of praziquantel among school children in northeast Ethiopia.MethodsA comparative cross-sectional study was conducted among 499 children of two preschool children. Stool specimens were collected and microscopically examined using Kato-Katz (41.7 gram) methods. Positive children were treated with a single oral dose of praziquantel at 40 mg/kg body weight. Egg reduction and cure rates were assessed 4 weeks post-treatment to evaluate the therapeutic efficacy of praziquantel against S. mansoni infection.ResultsThe overall prevalence of S. mansoni infection among the schoolchildren was 52.1% with a mean intensity of 546 eggs per gram of stool. Majorities of the S. mansoni infections were moderate to heavy intensity, with only 5.0% light infections. Praziquantel administered at a single oral dose of 40 mg/kg achieved a cure rate of 91.7% and reduced the egg rate by 86.8%. Twenty-one schoolchildren remained infected at 4 weeks post-treatment, among which 6 and 15 children had moderate and light infections, respectively.ConclusionsS. mansoni prevalence among primary school children in Northeast Ethiopia was high, highlighting the need to implement school-based chemotherapy with annual frequency. The efficacy of praziquantel at 40 mg/kg is sufficient to permit continued use in treating S. mansoni-infected schoolchildren.     

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.     

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.     

Water demand and schistosomiasis among the Gumau people of Bauchi State, Nigeria

A helminthological study of stool and urine samples from 1037 people from 4 rural communities in Gumau District of Bauchi State, Nigeria, was carried out using formol-ether concentration and direct centrifugation methods respectively. 39.0% of persons examined were infected. Ova of Ascaris lumbricoides, Schistosoma haematobium and S. mansoni were the most common. Trichuris trichiura, hookworm, tapeworm and Strongyloides stercoralis were also encountered. 17.9% and 10.8% of examined persons had S. haematobium and S. mansoni infections respectively. A significant relationship was found between water demand index (number of persons per well) and infection with S. haematobium (r = 0.95) and S. mansoni (r = 0.88) (P less than 0.01). Such a relationship was not found with other helminth infections. A significant association was also found between distance from a river and prevalence of S. haematobium (r = 0.94) and S. mansoni (r = 0.95) (P less than 0.01), but not with the other helminth infections. These findings suggest that the water demand index may be an important factor in the epidemiology of schistosome infections in rural communities.     

Tolerance of Kenyan Schistosoma mansoni to oxamniquine

Although 30 mg/kg oxamniquine produced high levels (85.5 to 99.5%) of egg reduction in Kenyan children infected with Schistosoma mansoni after a single oral treatment, cure rates from children at Mwea in Kirinyaga district were lower than those from Machakos (58% v. 74%). Redosing uncured children confirmed this lower cure rate (36% v. 83%). Isolates from infected children were passaged into mice and dosed with oxamniquine. Lower than expected reductions in worm numbers were obtained, suggesting that oxaminiquine tolerant S. mansoni are present in the normal worm population in Kenya. It is concluded that mass use of oxamniquine at 30 mg/kg may produce problems of drug resistance.     

Radioimmunoassay of serum conjugated cholic acid in hepatic murine schistosomiasis

Cholylglycine levels were measured by radioimmunoassay in sera from 10 control CFI female mice and 22 CFI female mice experimentally infected with Schistosoma mansoni. Cholylglycine was significantly elevated in sera of all but one of the chronically infected animals. Serum aspartate transaminase was within normal limits in all the infected animals; while five infected mice had elevated serum alkaline phosphatase and all these five also had high levels of serum cholylglycine. Marked hepatic histopathological changes were demonstrated in all the infected animals. The data suggest that serum cholylglycine is a highly sensitive index for hepatic dysfunction in chronic hepatic schistosomiasis mansoni.     

Comparative study of the effects of artemether and artesunate on juvenile and adult Schistosoma mansoni in experimentally infected mice

Artemether and artesunate, derivatives of the antimalarial artemisinin, also exhibit antischistosomal properties. There is a need to assess comparatively the activity of both compounds against different developmental stages of schistosome parasites. Since artemisinin derivatives will be increasingly used to treat malaria, it is important to study the effects of 7-day monotherapy regimens on schistosome infections. We carried out experiments with mice, infected with juvenile or adult Schistosoma mansoni, and treated with artemether or artesunate at various doses and regimens including those currently used for monotherapy of malaria. Three doses of artemether, at concentrations of 150 or 300 mg/kg, administered to mice with juvenile S. mansoni resulted in worm reductions of 88-97%, which were significantly higher than the 67-77% obtained with artesunate (P < 0.05). Total concentrations of 600 or 800 mg/kg artemether, administered over 2 or 4 consecutive days to mice with adult S. mansoni, reduced the worm burden significantly by 46-51% (P < 0.05). The reduction of the worm burden observed with artesunate was considerably lower, 24-33%, and not significant when compared with untreated control mice. Seven-day monotherapy regimens of artemether or artesunate given at different concentrations to mice with adult S. mansoni showed total worm reductions of 53-61% or 34-49%, respectively. We conclude that artemether and artesunate are efficacious antischistosomal agents, with artemether displaying consistently higher activities. Our findings may contribute to the current strategic discussions on the effect and use of artemisinin derivatives against schistosomes when they are used in malaria chemotherapy in areas of co-endemicity of both parasites.     

Re-assessing disability: the impact of schistosomal infection on daily activities among women in Gezira Province, Sudan.

Schistosoma mansoni is often perceived by governments and international aid agencies to present a major public health problem in the tropical and sub-tropical world. This perception persists in spite of the fact that biomedical practitioners and research workers disagree about the nature and extent of disease and disability caused by schistosomes. This paper raises the question of whether S. mansoni should continue to be given priority as a public health problem in Gezira Province, Sudan. Biomedical and continuous observational data are blended with ethnographic information in order to develop a more integrated picture of the impact of S. mansoni on daily activity patterns among women. Research took place in one village in the Gezira/Managil irrigation scheme. The study is characterized by a small sample and a paired design. That is, 11 infected women were paired with 11 uninfected women. These women were engaged in agricultural activities in the cotton picking season and they were matched for a wide range of social and economic factors that might otherwise have affected their working activities. Observations were conducted on a minute by minute basis in the cotton fields. These data, in combination with ethnographic information and data indicating female productive output, showed that infection with S. mansoni significantly altered activity patterns in the cotton fields. That is, infected women (with an arithmetic mean egg output of 1958 eggs/g) attempted to pick as much cotton as possible in the shortest time period feasible in the morning. This pattern was partially repeated by infected women who returned to the fields in the afternoon. However, a significant number of infected women felt too weak to sustain this work regime and the economic implications of this finding are discussed. Finally, Fisher's exact probability test showed that infected women were significantly less likely to undertake personal care activities between cotton picking sessions and this result suggests they may have been too tired and/or had a diminished perception of their own well-being. The implications of these results for public health policy in Gezira Province are discussed.     

Immunoglobulin M-specific serologic testing in an outbreak of foodborne viral hepatitis, type A

Ninety-seven symptomatic and five asymptomatic infections with viral hepatitis, type A (102 cases) were identified in members, guests and employees of a private country club in an outbreak associated with consuming food and ice prepared or handled by an employee of the club's kitchen pantry. Twenty-three symptomatic persons were tested by differential radioimmunoassay for immunoglobulin M (IgM) (acute-phase) hepatitis A antibody (anti-HAV) and all 23 were documented to be infected with hepatitis A virus (HAV). Forty-one member/guest cases had only a single exposure at the county club. Their incubation periods ranged from 21 to 40 days, with a mean of 30 days. The exposure of these single-day patrons occurred over a 14-day period. The index case was not icteric and only moderately symptomatic and was diagnosed retrospectively to have viral hepatitis, type A by serologic determination of IgM anti-HAV in blood samples. Four items implicated in disease transmission were potato salad, hot dogs, molded salmon and ice handled by the index case. Serologic screening of controls did not appear to alter the conclusions of the food item analysis.     

Antischistosomal activity of artemether in experimental Schistosomiasis mansoni

OBJECTIVE: To evaluate the effect of intramuscular injection of artemether in mice experimentally infected with Schistosoma mansoni, at the time of infection, during schistosomula maturation and after the beginning of egg-laying. METHODS: Eighty adult females Balb/c mice were divided into 8 groups with 10 animals each. Seven groups were infected with S. mansoni using 60 cercariae for each animal, inoculated subcutaneously, and the remaining group was maintained without infection. Among the seven infected groups, six were treated with artemether, according to the following schedule: three groups received doses of 100 mg/kg on days 0, 20 or 60 after inoculation of the cercariae; the other three received 50 mg/kg of artemether, also on days 0, 20 or 60. At the end of the 9th, 10th and 11th weeks after infection all the mice infected with S. mansoni were submitted to fecal examination using the Kato-Katz technique. On the 80th day of the experiment, the surviving animals were sacrificed and submitted to perfusion of the portal system in order to recover the worms. Body, liver and spleen weights of each animal were determined at that time. RESULTS: A reduction in egg-laying and the number of worms recovered was observed in mice treated with artemether (50 or 100 mg/kg) on the 20th day after infection. The decrease in the number of worms was more notable among S. mansoni females. A significant decrease in liver and spleen weights was also seen on the 20th day among animals treated with 50 or 100 mg/kg of artemether and also among those that received the drug at a dose of 50 mg/kg 60 days after infection. CONCLUSIONS: Evidence of the antischistosomal activity of artemether was shown, even at a dose of 50 mg/kg, when the drug was administered during the schistosomula maturation period in the portal system of the vertebrate host.     

Stimulation of hamster and human lymphocyte cultures by soluble egg antigens (SEA) of Schistosoma haematobium and S. mansoni.

Soluble egg and adult worm antigen preparations of Schistosoma haematobium and S. mansoni were tested in hamster and human lymphocyte cultures. Primed lymphocytes from infected donors showed a marked blastogenic response to the homologous antigens. A cross-reactivity to the heterologous antigens was seen especially in S. mansoni infected hamsters.     

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.     

The recognition of Schistosoma mansoni surface antigens by antibodies from patients infected with S. mansoni and S. haematobium

Polypeptide surface antigens of Schistosoma mansoni recognized by schistosomiasis patients have been identified and their strain and species specificity investigated. Antibodies from individuals infected with S. mansoni were used in immunoprecipitation assays of 125I-labelled schistosomulum surface antigens. All individuals surveyed from St. Lucia strongly precipitated antigens of approximately Mr 38,000 to 32,000 and 20,000. These antigens were shown by two-dimensional gel electrophoresis to be the same as those recognized by experimentally immunized mice. Although individuals showed a highly heterogeneous response against total polypeptide antigens synthesized in vitro by cell-free translation of adult S. mansoni mRNA, all individuals recognized the same surface antigens. Immunoprecipitation with sera from patients infected with S. mansoni in many different parts of Africa resulted in generally the same antigens being precipitated, although a very high molecular weight antigen(s), not strongly recognized by the St. Lucian sera was also precipitated by most of the African patient sera. One serum from Ghana precipitated the high molecular weight antigen but not the low molecular weight antigens, raising the possibility of the existence of S. mansoni strain(s) exhibiting some diversity in surface antigens. The surface of S. mansoni schistosomula was found to bind strongly antibodies from individuals infected with S. haematobium, demonstrating that most surface antigens are cross-reactive. Immunoprecipitation demonstrated, however, that of the polypeptide surface antigens only the very high molecular weight antigen was recognized by anti-S. haematobium antibodies and that the 38,000 to 32,000 and 20,000 Mr antigens were species-specific. Immunoprecipitation of the polypeptide antigens derived from purified adult surface membranes demonstrated recognition of the same 32,000, 25,000 and 20,000 Mr antigens recognized by chronically infected mice. Again these antigens were found to be species-specific.     

Non-human vertebrate hosts of Schistosoma haematobium and Schistosoma mansoni

The author reviews the results of experimental infections of various species of mammals, other than man, with S. haematobium and S. mansoni, and discusses investigations in Africa and Brazil into the possibility of the natural infection of non-human vertebrates with these two parasites. Only a few species, besides monkeys, could be easily infected with S. haematobium in the laboratory, while-outside man-natural infection with this parasite appears to be practically non-existent. On the other hand, many animals are good experimental hosts for S. mansoni, and at least 21 species of mammals have been found infected with this parasite in Africa and America. It is thus possible to state, provisionally, that man is the only reservoir of S. haematobium, but the question still remains open where S. mansoni is concerned. Further research is suggested in order to assess the importance of non-human reservoirs in the epidemiology of bilharziasis.     

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.     

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.     

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.     

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.     

The effect of multiple doses of antimonials in Schistosoma mansoni infection

The treatment of bilharziasis with antimonials has been carried out in the past in a rather arbitrary manner, dosage levels and schedules varying widely and being based on little valid experimental evidence. The author has therefore attempted to determine the optimum dosage intervals with tartar emetic for cure of mice experimentally infected with Schistosoma mansoni.     

A statewide outbreak of Cryptosporidium and its association with the distribution of public swimming pools

In order to characterize the association between county-level risk factors and the incidence of Cryptosporidium in the 2007 Iowa outbreak, we used generalized linear mixed models with the number of Cryptosporidium cases per county as the dependent variable. We employed a spatial power covariance structure, which assumed that the correlation between the numbers of cases in any two counties decreases as the distance between them increases. County population size was included in the model to adjust for population differences. Independent variables included the number of pools in specific pool categories (large, small, spa, wading, waterslide) and pool-owner classes (apartment, camp, country club or health club, hotel, municipal, school, other) as well as the proportion of residents aged <5 years. We found that increases in the number of bigger pools, pools with more heterogeneous mixing (municipal pools vs. country club or apartment pools), and pools catering to young children (wading pools) are associated with more cases at the county level.