Pathology of the spleen in hepatosplenic schistosomiasis. Morphometric evaluation and extracellular matrix changes.
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Histological, ultrastructural, morphometric and immunohistochemical data obtained from the study of spleens removed by splenectomy from 34 patients with advanced hepatosplenic schistosomiasis revealed that the main alterations were congestive dilatation of the venous sinuses and diffuse thickening of the splenic cords. Splenic cord thickening was due to an increase of its matrix components, especially type IV collagen and laminin, with the conspicuous absence of interstitial collagens, either of type I or type III. Deposition of interstitial collagens (types I and III) occurred in scattered, small focal areas of the red pulp, but in the outside of the walls of the venous sinuses, in lymph follicles, marginal zone, in the vicinity of fibrous trabeculae and in sidero-sclerotic nodules. However, fibrosis was not a prominent change in schistosomal splenomegaly and thus the designation "fibro-congestive splenomegaly" seems inadequate. Lymph follicles exhibited variable degrees of atrophy, hyperplasia and fibrous replacement, sometimes all of them seen in different follicles of the same spleen and even in the same examined section. Changes in white pulp did not seem to greatly contribute to increasing spleen size and weight, when compared to the much more significant red pulp enlargement. (+info)
Planning chemotherapy based schistosomiasis control: validation of a mathematical model using data on Schistosoma haematobium from Pemba, Tanzania.
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A mathematical model, based on a deterministic differential equation framework, has been developed to predict the impact of community chemotherapy programmes for human schistosomiasis. Here, this model is validated using data collected from a long-term control programme for urinary schistosomiasis on the island of Pemba, Zanzibar, United Republic of Tanzania, initiated in 1986 and still ongoing, in which schoolchildren were offered praziquantel chemotherapy every 6 months. Prevalence of infection and blood in urine were monitored in all the schools (total 26000 children from 60 schools) and more detailed data were collected in selected evaluation schools. Model predictions were run by using the initial prevalence as input. The predictions were very close to the observed decreases in prevalence and in prevalence of blood in urine. The correspondence improved further when the data were combined, going from single school level to district, and when the entire data set was combined. The accuracy of the predictions suggests that this model could be used as a tool to predict the consequences of chemotherapy control programmes. It is currently in press as a Windows software package under the name of 'EpiSchisto'. (+info)
Plasmodium falciparum histidine-rich protein 2-based immunocapture diagnostic assay for malaria: cross-reactivity with rheumatoid factors.
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Recently introduced rapid nonmicroscopic immunocapture assays for the diagnosis of malaria infection are being evaluated for their sensitivity and specificity in various epidemiological settings. A Plasmodium falciparum histidine-rich protein 2 (PfHRP-2)-based assay (ICT) and a Plasmodium-specific lactate dehydrogenase test (OptiMAL) were evaluated for their specificities in different groups of patients who tested negative for malaria infection by microscopy. The patients were selected from different disease groups: rheumatoid arthritis, hepatitis C, toxoplasmosis, schistosomiasis, and hydatid disease. One hundred thirty-three of the 225 patients were positive for rheumatoid factor. Thirty-five of the 133 (26%) rheumatoid factor-positive patients gave a false-positive reaction with the ICT assay, but only 4 of these gave false-positive reactions with the OptiMAL test. Thirty-three of the 35 false-positive specimens became negative when repeat tested with the ICT assay after absorbing out the rheumatoid factor activity. Our study shows that the PfHRP-2-based ICT assay gave a false-positive reaction in 26% of the patients who had rheumatoid factors, but were negative for malaria by microscopy. (+info)
Female genital schistosomiasis of the lower genital tract: prevalence and disease-associated morbidity in northern Tanzania.
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Female genital schistosomiasis (FGS) is a neglected disease manifestation of schistosomiasis. A cross-sectional study was carried out to assess in a schistosomiasis-endemic area the proportion of women affected by FGS of the lower reproductive tract and to compare the frequency of symptoms and signs possibly associated with FGS between women with proven FGS (n=134), endemic referents (n=225, women living in an endemic site), and referents (n=75, women living in a nonendemic site). Urinary schistosomiasis was diagnosed in 36% (239/657) and FGS in 37% (134/359) of the women. Cervical lesions occurred in 75% of the FGS cases, in 48% of endemic referents, and in 36% of nonendemic referents. The high prevalence of FGS in all age groups and the high levels of pathologic cervical alterations such as swollen and disrupted epithelium support the hypothesis that FGS might be a risk factor for the transmission of human immunodeficiency virus. (+info)
The immunofluorescence antibody test (IFAT) for the diagnosis of schistosomiasis used in a non-endemic area.
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OBJECTIVE: To evaluate an immunofluorescence antibody test (IFAT) for diagnosis of schistosomiasis in nonimmune travellers and immigrants from endemic areas. METHODS: 65 patients (48 Danes and 17 immigrants) with schistosomiasis were included. The diagnosis of schistosomiasis was based on the presence of schistosome eggs in faeces, urine, sperm, rectal or bladder biopsies and/or the presence of specific antibodies determined by the serological immunofluorescence antibody test (IFAT). Egg excretion was detected using conventional methods and the IFAT performed on whole S. mansoni schistosomula worms, harvested after 8 weeks from mice. Two patterns of immunofluorescence were observed: Fluorescence in the gut of the schistosome called 'Gut Associated Antigen, GAA', and fluorescence of the surface of the schistosomula called 'Membrane Bound Antigen, MBA'. RESULTS: Eggs were found in 44% of the Danish patients and in 76% of immigrants. The diagnosis was based on a positive IFAT in 48% of the patients. In patients from nonendemic areas, the finding of antibodies against GAA was diagnostic while optimal sensitivity in the immigrants was reached by measuring antibodies against both GAA and MBA. CONCLUSION: In patients from nonendemic areas GAA is a sensitive marker of acute infection with schistosomiasis. In patients from endemic areas the demonstration of both GAA and MBA is necessary to properly identify long-lasting, nonacute infections. Egg-detection and/or measurement of CAA and CCA remain the methods of choice to monitor treatment as the immunofluorescence assay may remain positive for several years after treatment. (+info)
IL-4 regulates VIP receptor subtype 2 mRNA (VPAC2) expression in T cells in murine schistosomiasis.
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In murine schistosomiasis, granuloma T cells express VPAC2 mRNA, whereas there is none in splenocytes. This suggests that T cell VPAC2 mRNA is inducible. To address this issue, splenocytes from schistosome-infected mice were incubated with anti-CD3 to induce VPAC2 mRNA, which only appeared when cell cultures also contained anti-IL-4 mAb. Granuloma cells expressed VPAC2 mRNA. This natural expression decreased substantially when cells were cultured 3 days in vitro. However, granuloma cells cultured with anti-IL-4 mAb strongly expressed VPAC2 mRNA. IL-4 KO mice were examined to further address the importance of IL-4 in VPAC2 regulation. Splenocytes and dispersed granuloma cells from IL-4 KO animals had substantially more VPAC2 mRNA than those in wild-type controls. VPAC2 mRNA content decreased when cells were cultured with rIL-4. VPAC2 mRNA localized to CD4+ T cells. Th1 cell lines expressed VPAC2 mRNA much stronger than Th2 cells. Anti-IL-4 mAb increased VPAC2 mRNA expression in Th2 cells cultured in vitro. However, rIL-4 could not suppress VPAC2 mRNA expression in Th1 cells. Thus, VPAC2 is an inducible CD4+ T cell receptor, and IL-4 down-modulates VPAC2 mRNA expression in Th2 cells. (+info)
Microhabitat preferences of Biomphalaria pfeifferi and Lymnaea natalensis in a natural and a man-made habitat in southeastern Tanzania.
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Schistosoma mansoni is an important human parasitic disease which is widespread throughout Africa. As Biomphalaria pfeifferi snails act as intermediate host, knowledge of their population ecology is an essential prerequisite towards understanding disease transmission. We conducted a field study and assessed the density and microhabitat preferences of B.pfeifferi in a natural habitat which was a residual pool of a river. Repeated removal collecting revealed a density of 26.6 [95% confidence interval (CI): 24.9-28.3] snails/m2. B. pfeifferi showed microhabitat preferences for shallow water (depths: 0-4cm). They were found most abundantly close to the shoreline (distances: 0-40cm), and preferred either plant detritus or bedrock as substratum. Lymnaea natalensis, a snail which may act as a host for human Fasciola gigantica, also occurred in this habitat with a density of 34.0 (95% CI: 24.7-43.3) snails/m2, and preferred significantly different microhabitats when compared to B.pfeifferi. Microhabitat selection by these snail species was also investigated in a man-made habitat nearby, which consisted of a flat layer of concrete fixed on the riverbed, covered by algae. Here, B.pfeifferi showed no preference for locations close to the shoreline, probably because the habitat had a uniform depth. We conclude that repeated removal collecting in shallow habitats provides reliable estimates of snail densities and that habitat changes through constructions may create favourable microhabitats and contribute to additional disease transmission. (+info)
Rapid screening for Schistosoma mansoni in western Cote d'Ivoire using a simple school questionnaire.
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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 Cote 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. (+info)