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At least 19 recordsLinked to original sources

PubMed2002

Schistosomiasis control in the 21st century. Proceedings of the International Symposium on Schistosomiasis, Shanghai, July 4-6, 2001.

A total of 120 papers were presented at the International Symposium on Schistosomiasis which was held in Shanghai, July 4-6, 2001 with the theme of Schistosomiasis Control in the 21st Century. In order to focus more attention on the new challenges in control programmes for schistosomiasis as well as show the priority of research areas in new century, we summarize the advances of control programmes and researches in nine areas, including (1) Status of schistosomiasis control programmes; (2) Progress in applied field research; (3) Biology and control approaches of snail hosts; (4) Novel approaches for schistosomiasis control; (5) Pathogenesis and morbidity of the disease; (6) Immunology and vaccine development; (7) Screening of population for chemotherapy in low transmission areas; (8) Sustainable intervention methods in different endemic settings; (9) Impact of animal schistosomiasis on agricultural development and importance of its control; (10) GIS/RS application and environmental changes.

Animals↗

PubMed2025

The impact of Schistosoma haematobium hybridization on molecular diagnosis of schistosomiasis: A review with emphasis on female genital schistosomiasis.

Female genital schistosomiasis (FGS) is a gynecological manifestation of urinary schistosomiasis in female genitals. FGS is a neglected tropical disease; not only are most patients unaware of the condition, but healthcare workers and policymakers have inadequate knowledge about it. The treatment and control of FGS relies on current guidelines for controlling and eliminating schistosomiasis without rigorous focus on clinical evidence of the presence of FGS. Neglect of FGS has led to the misconception that the disease is sexually transmitted. Diagnosing FGS remains challenging as there is no widely accepted reference assay. Urine examination, which is the gold standard in urogenital schistosomiasis has some limitations in diagnosing FGS as the demonstration of Schistosoma haematobium and/or eggs alone does not necessarily indicate FGS. In order to overcome challenges with the biopsy and colposcopy approach, some studies have evaluated the potential of PCR-based assays and isothermal amplification of Schistosoma DNA. Recent studies have reported hybridization between S. haematobium and other livestock schistosomes, but little is known about the impact of hybridization on schistosomiasis diagnosis. These hybrids not only affect livestock and humans but also have their genomes modified, and in some cases, abnormal egg morphology due to Schistosoma hybridization might affect the actual prevalence estimation. Herein, we highlight the potential impacts of S. haematobium hybridization on molecular diagnosis of schistosomiasis, with an emphasis on FGS.

Humans↗

PubMed2000

[Reduced morbidity of schistosomiasis: report from an expert workshop on the control of schistosomiasis held at CERMES (15-18 February 2000, Niamey, Niger)].

Schistosomiasis remains a problem for public health in sub-Saharan Africa. Despite past efforts, cases have not decreased significantly. Schistosoma haematobium and S. mansoni are endemic in all the West African countries. The distribution of both parasites is focal. During a workshop held at CERMES in Niamey, in February 2000, a group of experts recommended that schistosomiasis control be considered as a public health priority in all the endemic West African countries, and National Control Programmes rapidly implemented. The objective of these control programmes would be to reduce schistosomiasis-related morbidity. Case detection should be based on clinical symptoms such as haematuria or bloody diarrhoea, and be carried out at two levels: health care centres and schools, in order to reach patients and school-age children. Health workers should be trained in case detection and community based control of schistosomiasis. The assembled experts advocated the use of praziquantel dosed at 40 mg.kg-1, which therefore must be made available and accessible in outlying areas. Associated measures consist of sanitation, water supply and health education, especially aimed at improving patients' treatment-seeking behaviour. A West African network for schistosomiasis control was created during the workshop. It runs on the Web site of CERMES as network co-ordinator. (http://www.mpl.ird.fr/cermes/).

Africa South of the Sahara↗

PubMed1993

Public health impact of schistosomiasis: disease and mortality. WHO Expert Committee on the Control of Schistosomiasis.

The public health significance of schistosomiasis is often underestimated for two reasons. First, like all helminthic infections, the distribution of worms in any community is widespread but uneven, i.e., few have heavy infections and severe disease, while many have lighter infections and fewer symptoms. Some people with very few worms may have no symptoms. Secondly, severe disease usually follows after many years of silent or mildly symptomatic infection. Even if only 10% of those 200 million infected with schistosomiasis have severe clinical disease, this still represents 20 million seriously ill people. Of the remaining 180 million infected people, an estimated 50-60% also have symptoms--a public health problem of enormous proportions. The impact on public health can be assessed in terms of the frequency and severity of schistosomiasis-related disease, incapacity and premature death. This article presents extracts from the Expert Committee's recently published second report and deals with morbidity and mortality, as well as the links between schistosomiasis and cancer, nutrition and intercurrent infections, and the immune response to schistosomiasis.

Communicable Disease Control↗

PubMed2003

Transmission of schistosomiasis in Kariba, Zimbabwe, and a cross-sectional comparison of schistosomiasis prevalences and intensities in the town with those in Siavonga in Zambia.

Given that the two communities lie only 10 km apart, on the northern shore of Lake Kariba, it is surprising that human schistosomiasis now appears to be a much less important health problem in Kariba town (Zimbabwe) than in Siavonga town (Zambia). In an attempt to explain this difference, the level and sites of Schistosoma haematobium and S. mansoni transmission in Kariba, and the prevalences and intensities of human infection with these parasites in both communities, have now been investigated. In a longitudinal study, a cohort of 378 schoolchildren, 150 subsistence fishermen and 42 commercial fishermen from Kariba town was screened three times for schistosome infection, at 6-month intervals. Sixteen human-water contact sites in or near the town were surveyed for intermediate host snails every month for 1 year. Finally, the results of screening 660 Kariba schoolchildren (in January 2001) and 527 Siavonga schoolchildren (in July 2002) were compared. In the longitudinal study, 9.0% of the schoolchildren, 7.3% of the subsistence fishermen and 0% of the commercial fishermen were each found positive for S. haematobium at least once. The corresponding values for S. mansoni were 2.5%, 12.5% and 26.3%, respectively. The results indicated that, each year in Kariba, 2.4% and 2.0% of schoolchildren and 18.2% and 5.2% of fishermen were infected with S. haematobium and S. mansoni, respectively. Although both Bulinus globosus and Biomphalaria pfeifferi were found at 14 of the 16 water-contact sites, snails infected with schistosomes that could infect mammals were only found at three of the sites. The problem of schistosomiasis in Kariba town appears to be greater among fishermen than schoolchildren, all transmission probably occurring in Lake Kariba. As expected, the overall prevalences of S. haematobium and S. mansoni infection among Siavonga schoolchildren (19.4% and 33.5%, respectively) were far higher than the corresponding values for Kariba schoolchildren (7.1% and 2.1%, respectively). The marked differences in the prevalence of human schistosomiasis between Kariba and Siavonga appear to be attributable to the better water and sanitation facilities and a history of schistosomiasis-control activities in Kariba town.

Adolescent↗

PubMed2003

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.

Adolescent↗

PubMed1998

Studies on schistosomiasis in western Kenya: II. Efficacy of praziquantel for treatment of schistosomiasis in persons coinfected with human immunodeficiency virus-1.

Praziquantel is the drug of choice for schistosomiasis chemotherapy. Although the exact mechanism of how praziquantel kills schistosomes remains poorly understood, the immune response of the host is an important factor in drug efficacy. It is thus possible that disease states of humans that lead to immunodeficiencies, such as infection with human immunodeficiency virus-1 (HIV-1), may render praziquantel less effective in treating schistosomiasis. To test this hypothesis, persons with high levels of Schistosoma mansoni infection who were or were not also infected with HIV-1 were treated with a standard regimen of praziquantel and monitored by quantitative fecal examination and plasma circulating cathodic antigen. Both groups responded to praziquantel therapy equally and individuals with low percentages (< 20%) of CD4+ T cells did not differ from individuals with higher CD4 cell percentages. These data demonstrate that persons with HIV-1 infection can be treated effectively for schistosomiasis with praziquantel.

Animals↗

PubMed1983

Immune responses during human schistosomiasis mansoni. X. Production and standardization of an antigen-induced mitogenic activity by peripheral blood mononuclear cells from treated, but not active cases of schistosomiasis.

Peripheral blood mononuclear cells (PBMN) from patients with active schistosomiasis mansoni are generally induced to proliferate upon exposure to a soluble worm antigenic preparation (SWAP). In contrast, only 25% of such patients responded to SWAP exposure by the production of detectable levels of a mitogenic factor (MF) activity capable of stimulating proliferation of resting cultures of allogeneic PBMN. When former schistosomal patients (chemotherapeutically cured 10 to 40 yr previously) were tested for these two responses to SWAP, all manifested blastogenesis; 80% also responded by the production of MF activity. Only 9% of control subjects with no history of schistosomiasis produced MF activity when exposed to SWAP. The production and assay of MF activity by former schistosomiasis patients was standardized. Reliable, optimal production was achieved by using 6 X 10(6) PBMN in 2-ml cultures upon exposure to 15 micrograms protein SWAP/ml. The cells were incubated for 20 hr in the presence or absence of SWAP, at which time they were washed and recultured in fresh medium for at least 28 more hours. Subject to subject variability occurred in the optimal time of detection of MF activity in culture supernatant fluids, but detection was assured between 24 and 48 hr after the wash. The assay system for MF detection required a 5 to 7-day culture. The consistent production of MF activity by former schistosomal patients emphasized the longevity of immunologic memory to SWAP, and may indicate a post-treatment decline of immunoregulatory mechanisms that are operative in patients with active schistosome infections.

Antigens↗

PubMed1990

Human schistosomiasis in Cameroon. I. Distribution of schistosomiasis.

The status of schistosomiasis in Cameroon was examined in a nationwide survey of 5th grade schoolchildren. Five hundred twelve schools were surveyed; 19,524 urine and 22,166 stool samples were examined. The 3 northern provinces, which comprised 29% of the population, had 87% of all urinary and 82% of all intestinal cases. These provinces have a low seasonal rainfall. The presence of temporary bodies of water and of molluscan intermediate hosts adapted to this environment permits intense transmission of schistosomiasis haematobium and mansoni. In the rest of the country, the distribution of Schistosoma haematobium and S. mansoni was highly focal. S. intercalatum endemic areas were restricted to the equatorial forest and were small with low prevalences and intensities.

Adolescent↗

PubMed1978

Epidemiology and control of schistosomiasis: present situation and priorities for further research. Scientific Working Group on Schistosomiasis.

The article highlights specific aspects of the epidemiology of schistosomiasis where insufficient data are available on which to base appropriate control strategies. Emphasis is placed on the part that immunological techniques might play in improving the baseline epidemiological data. A study of acquired resistance to the disease is also important in relation to epidemiology and control. The clinical manifestations of the disease vary in different areas and further study of the relation between the clinical and pathological manifestations are therefore required. In relation to the intermediate host, the main priority for research concerns the definition of the location and time-patterns of transmission foci within any particular area: variations in transmission are of particular importance in relation to man-made water resources. Although chemotherapy will play an increasing role in control, its importance will depend on local conditions: coordinated and standardized trials are required of chemotherapeutic agents in different regions and in various defined groups of subjects. The effects of chemotherapy on immunity to reinfection and on immunopathology also require study. With all types of snail control-chemical, ecological, and biological-cost-effectiveness aspects are important. With chemicals, it is important to bear in mind other possible effects on the environment. In the field of water supplies and sanitation, several aspects are important in relation to schistosomiasis transmission and community involvement should be encouraged.

Ecology↗

PubMed1983

Immunodiagnosis of Schistosomiasis haematobium and schistosomiasis mansoni in man. Application of crude extracts from adult worms and cercariae in the IHA and the ELISA.

The antibody responses of patients infected with S. haematobium or S. mansoni were investigated in an indirect hemagglutination test (IHA) and an enzyme linked immunosorbent assay (ELISA) using crude extracts of cercariae and adult worms of S. haematobium and S. mansoni, and of adult worms of S. japonicum. Patients were Africans from endemic areas, as well as Europeans who had acquired their infection relatively recently. Although the IHA showed a similar pattern of antibody responses as the ELISA it was less sensitive to assess recently acquired infections. Of special interest, antibodies found in patients with schistosomiasis mansoni cross-reacted strongly with antigens extracted from adult S. haematobium and S. japonicum. In contrast, sera of patients with schistosomiasis haematobium reacted significantly better with the homologous antigen than with heterologous antigens. In the ELISA the ratio of the absorption values of anticercarial antibodies to antiworm antibodies could be used to discriminate chronic from recent infections.

Africa↗

PubMed1983

Immunologic studies of human schistosomiasis. I. Clinical and immunological findings in acute and chronic schistosomiasis.

Sera and ascitic fluid of 26 patients with acute and chronic schistosomiasis were studied for the presence of circulating immune complexes (CIC's), IgG, IgM, IgA, complement C3 and C4, as well as their correlation with the clinical manifestations of the disease. Serum levels of CIC's and IgG were significantly increased in patients with acute S. mansoni and S. haematobium infections and in patients with chronic schistosomiasis. Serum IgA levels were evaluated in 20% of patients with S. mansoni infection, 67% with S. haematobium infections and in 100% of chronically infected patients. Complement C3 levels were normal in all patients. Ascitic fluid analysis revealed the presence of IgG, IgM, IgA, C3 and C4 and high concentrations of CIC's. A significant positive correlation was demonstrated to occur between serum CIC's and IgG, as well as between the serum and ascitic fluid levels of CIC's of chronic patients. These findings also correlated with the degree and severity of the clinical syndrome.

Acute Disease↗

PubMed1983

Immunologic studies of human schistosomiasis. II. Interrelationship of serum and ascitic fluid histamine, IgE and total eosinophils in acute and chronic human schistosomiasis.

Sera and ascitic fluid of 26 patients with acute and chronic schistosomiasis were studied for the determination of histamine levels, IgE and total eosinophil counts and their correlation with the clinical manifestations of the disease. Serum histamine levels were significantly increased in acute and chronically infected patients. Serum IgE levels were markedly increased in all patients with S. mansoni infection and S. haematobium infection and moderately elevated in chronic patients. Eosinophilia was found in 60% of patients with S. mansoni infection and in 83% with S. haematobium infection. Ascitic fluid analysis revealed the presence of IgE and high concentrations of histamine. There was also a significant positive correlation (p less than 0.01) between serum and ascitic fluid histamine levels, as well as to IgE levels. These results support the contention that histamine and other immune system components may play a role in the pathophysiology of different stages of schistosomiasis.

Acute Disease↗

PubMed1981

Modulation of in vitro lymphocyte proliferation in patients with Schistosomiasis haematobium, Schistosomiasis mansoni and mixed infections.

Cell-mediated immunity to mitogens, nonparasitic and parasitic antigens was evaluated by means of in vitro lymphocyte proliferation in 37 African patients infected with S. haematobium, S. mansoni, or both parasites as well as in an uninfected control group. Lymphocytes of patients with schistosomiasis mansoni or schistosomiasis haematobium monoinfection could be similarly stimulated by a delipidized extract of S. mansoni adults. There was also no difference in lymphocyte responsiveness to stimulation by PHA, PWM, ConA, and PPD between these groups and as compared with uninfected controls. In the mixed infection patient group, stimulation by mansoni antigen - as well as by PPD, PHA, PWM - was significantly suppressed (p less than 0.01). Of particular interest, in cultures stimulated by the specific antigen the degree of in vitro suppression was inversely correlated to the intensity of infection (r = 0.54, p less than 0.025).

Adolescent↗

PubMed2000

Observation of T lymphocyte subsets in the liver of patients with advanced schistosomiasis and advanced schistosomiasis accompanied with hepatitis B.

T lymphocyte subsets in the liver were detected by Avidin-Biotin Complex (ABC) assay in 22 patients with advanced schistosomiasis (AS) and 5 cases of AS accompanied with hepatitis B. T lymphocytes in the liver of AS patients were distributed in the peripheral layer of egg granuloma or the area near eggs in non-granuloma. No infiltrative T lymphocytes were observed in area with extensive fibrosis. There was infiltration of many T cells in the portal tract, piecemeal and focal necrosis area as well as in hepatic sinus in AS patients accompanied with hepatitis B. CD8+ T cells (suppressor/cytotoxic T cells, Ts/Tc) in the liver were predominant in the two groups. In AS patients, marked hepatic fibrosis, a small number of T cell infiltration and slight hepatocellular degeneration and necrosis were observed. However, obvious hepatocellular degeneration and necrosis were seen in AS patients accompanied with hepatitis B, and 3 cases of them developed active liver cirrhosis. The results indicated immune response was weak in the liver in AS patients and Ts cells might be predominant in the subset of CD8+ T lymphocytes. Cellular immune response was relatively strong in AS patients accompanied with hepatitis B and the infiltrative CD8+ T lymphocytes might be mainly Tc cells.

Adolescent↗

PubMed1985

A clinico-epidemiological survey of schistosomiasis mansoni in a hyperendemic area in Minas Gerais State (Comercinho, Brazil). I. Differences in the manifestations of schistosomiasis in the town centre and in the environs.

A cross-sectional survey of schistosomiasis was done in Comercinho (Minas Gerais State, Brazil). Faecal (Kato-Katz technique) and physical examinations were performed on 90% and 79% of the population (1474 inhabitants), respectively. The rate of infection with Schistosoma mansoni was 70%, the geometric mean of eggs was 334/g of faeces and 7% of the infected individuals had splenomegaly. The rate of infection, faecal egg counts and the rate of splenomegaly were significantly higher in the environs (zones 3 and 4) of the town than in the central areas (zones 1 and 2) of Comercinho. This difference seemed to be determined by the social differences existing between the population in the central area and the environs; in the environs the heads of families were predominantly manual workers (73 and 94% respectively), only 10 and 3% of the houses had piped water supply and less than 14% were of better quality.

Adolescent↗

PubMedDate not supplied

School-based schistosomiasis control programmes: a comparative study on the prevalence and intensity of urinary schistosomiasis among Nigerian school-age children in and out of school.

A cross-sectional study was conducted in February 1998 on the prevalence and intensity of urinary schistosomiasis among school-age children in and out of school at Adim village in Nigeria to test the objective of delivering a control programme through the school system. School enrollment figures and non-attendance rate were collated from questionnaires that were self-administered by heads of families. Prevalence and intensity of infection were determined following filtration of urine and counting of carbol fuchsin-stained eggs of Schistosoma haematobium. The rates of regular school attendance, irregular attendance and non-attendance were 69.1%, 5.1%, and 25.8%, respectively. These indices were not significantly associated with the age of the schoolchildren (P > 0.05). Boys (76.6%) were more associated with regular attendance than girls (61.4%) (P < 0.0001) while girls had a higher rate of non-attendance (32.7%) than males (19.1%) (P < 0.0001). Although more out-of-school children were infected (90.7%) than those in school (86.8%), the difference was not statistically significant (P > 0.05). The same association was established in the variation of mean egg count between the 2 study populations though intensity was higher among out-of-school children. The principal reasons proffered for the high rate of non-attendance listed in their order of importance were: economic, sickness, poor performance, refusal, farming and fishing. A dual method of control that would in incorporate the integration of recognized local authorities is suggested in areas with moderate school attendance rate like Adim, as lack of treatment of infected out-of-school children ensures continuous contamination and re-infection.

Adolescent↗

PubMed1986

Hepatocellular carcinoma and schistosomiasis japonica. A clinicopathologic study of 59 autopsy cases of hepatocellular carcinoma associated with chronic schistosomiasis japonica.

The association between hepatocellular carcinoma (HCC) and chronic hepatic schistosomiasis (CS) was studied by reviewing, 4,886 autopsies in adults during the past 20 years. In 229 cases of CS, 59 (25.7%) also had HCC. Among cases without CS, 399 (8.5%) had HCC. The incidence of HCC in patients with CS was significantly higher than that of other autopsy cases (p less than 0.01). Serum HBsAg was positive in 25.7% of 35 HCC cases with CS examined for hepatitis B virus (HBV) markers and anti HBs was positive in 10 of the 12 HBsAg-negative cases associated with CS, and in 62.1% of the other HBsAg-negative cases examined. Thus, most of HCC cases, including those associated with CS, probably had HBV infection at one time. Morphological examination revealed varying degrees of non-schistosomal hepatic changes, including macronodular or mixed macro-and micronodular cirrhosis, superimposed on schistosomal fibrosis in about two-thirds of the cases of HCC associated with CS. Although conclusive evidence whether or not schistosomal infection had a direct role in hepatocarcinogenesis could not be obtained, it was predicted that the additional non-schistosomal factors, particularly HBV infection, might play a synergistic role.

Adult↗