Effective Control of Schistosoma haematobium Infection in a Ghanaian Community following Installation of a Water Recreation Area

BackgroundUrogenital schistosomiasis caused by Schistosoma haematobium was endemic in Adasawase, Ghana in 2007. Transmission was reported to be primarily through recreational water contact.MethodsWe designed a water recreation area (WRA) to prevent transmission to school-aged children. The WRA features a concrete pool supplied by a borehole well and a gravity-driven rainwater collection system; it is 30 m2 and is split into shallow and deep sections to accommodate a variety of age groups. The WRA opened in 2009 and children were encouraged to use it for recreation as opposed to the local river. We screened children annually for S. haematobium eggs in their urine in 2008, 2009, and 2010 and established differences in infection rates before (2008–09) and after (2009–10) installation of the WRA. After each annual screening, children were treated with praziquantel and rescreened to confirm parasite clearance.Principal FindingsInitial baseline testing in 2008 established that 105 of 247 (42.5%) children were egg-positive. In 2009, with drug treatment alone, the pre-WRA annual cumulative incidence of infection was 29 of 216 (13.4%). In 2010, this incidence rate fell significantly (p<0.001, chi-squared) to 9 of 245 (3.7%) children after installation of the WRA. Logistic regression analysis was used to determine correlates of infection among the variables age, sex, distance between home and river, minutes observed at the river, low height-for-age, low weight-for-age, low Body Mass Index (BMI)-for-age, and previous infection status.Conclusion/SignificanceThe installation and use of a WRA is a feasible and highly effective means to reduce the incidence of schistosomiasis in school-aged children in a rural Ghanaian community. In conjunction with drug treatment and education, such an intervention can represent a significant step towards the control of schistosomiasis. The WRA should be tested in other water-rich endemic areas to determine whether infection prevalence can be substantially reduced.Author SummaryUrogenital schistosomiasis is a disease caused by the parasite Schistosoma haematobium; it is often characterized by bloody urine and tends to disproportionately affect school-aged children in rural tropical regions. The parasite is transmitted via skin contact with surface water that is contaminated by human waste. The disease was endemic in Adasawase, a rural Ghanaian community, in 2007. Transmission occurred mainly through recreational water contact. We collaborated with community members to design a water recreation area (WRA) featuring a concrete pool supplied by a borehole well and a rainwater collection system. We opened the pool in 2009 and local officials encouraged children to use the WRA for recreation. We screened local children annually (2008, 2009, 2010) for S. haematobium infection. After each screening, children were treated with praziquantel and rescreened. Baseline testing in 2008 established that at least 105 of 247 (42.5%) children were infected. In 2009, 29 of 216 (13.4%) children were infected, reflecting annual cumulative incidence. In 2010, a significantly smaller percentage of children (9 of 245, 3.7%) were infected. We conclude that the WRA effectively reduced infection in Adasawase, and that it should be tested in other water-rich endemic areas

Cytokine responses to Schistosoma haematobium in a Zimbabwean population: contrasting profiles for IFN-γ, IL-4, IL-5 and IL-10 with age

<p>Abstract</p> <p>Background</p> <p>The rate of development of parasite-specific immune responses can be studied by following their age profiles in exposed and infected hosts. This study determined the cytokine-age profiles of Zimbabweans resident in a <it>Schistosoma haematobium </it>endemic area and further investigated the relationship between the cytokine responses and infection intensity.</p> <p>Methods</p> <p>Schistosome adult worm antigen-specific IFN-γ, IL-4, IL-5 and IL-10 cytokine responses elicited from whole blood cultures were studied in 190 Zimbabweans exposed to <it>S. haematobium </it>infection (aged 6 to 40 years old). The cytokines were measured using capture ELISAs and the data thus obtained together with <it>S. haematobium </it>egg count data from urine assays were analysed using a combination of parametric and nonparametric statistical approaches.</p> <p>Results</p> <p>Age profiles of schistosome infection in the study population showed that infection rose to peak in childhood (11–12 years) followed by a sharp decline in infection intensity while prevalence fell more gradually. Mean infection intensity was 37 eggs/10 ml urine (SE 6.19 eggs/10 ml urine) while infection prevalence was 54.7%. Measurements of parasite-specific cytokine responses showed that IL-4, IL-5 and IL-10 but not IFN-γ followed distinct age-profiles. Parasite-specific IL-10 production developed early, peaking in the youngest age group and declining thereafter; while IL-4 and IL-5 responses were slower to develop with a later peak. High IL-10 producers were likely to be egg positive with IL-10 production increasing with increasing infection intensity. Furthermore people producing high levels of IL-10 produced little or no IL-5, suggesting that IL-10 may be involved in the regulation of IL-5 levels. IL-4 and IFN-γ did not show a significant relationship with infection status or intensity and were positively associated with each other.</p> <p>Conclusion</p> <p>Taken together, these results show that the IL-10 responses develop early compared to the IL-5 response and may be down-modulating immunopathological responses that occur during the early phase of infection. The results further support current suggestions that the Th1/Th2 dichotomy does not sufficiently explain susceptibility or resistance to schistosome infection.</p

Comparison of pyrimidine and purine nucleoside secretion and nucleoside kinase expression in resident and elicited peritoneal macrophages.

Abstract Thymidine was found in culture supernatants from both normal peritoneal macrophages and macrophages elicited in vivo with LPS under conditions in which there was no detectable TK activity. Abrogation of thymidine secretion was observed only when elicited macrophages were cultured in the presence of macrophage growth factor (MGF), whereas resident macrophages continued secreting under similar conditions. Similarly, TK activity was induced with MGF only in elicited, but not in resident, macrophages; LPS added in vitro failed to render resident macrophages susceptible to stimulation by MGF. Tests for adenosine and deoxyadenosine in macrophage supernatants proved that these nucleosides were not secreted by these cells. Although AK was consistently expressed in both resident and elicited macrophages, no significant dAK levels could be detected in either cell population. In contrast to TK, both purine nucleoside kinases could not be modulated or induced with MGF. The data indicate different reactivity to MGF by resident and elicited macrophages and a difference in pyrimidine vs purine nucleoside secretion as well as nucleoside kinase expression by these cells.</jats:p

Characterization and antigen-presenting function of a murine thyroid-derived epithelial cell line.

Abstract We have developed and evaluated the antigen-presenting function of a murine thyroid-derived epithelial cell line M.5 in order to further investigate the possible role of the thyroid follicular epithelium in the inductive phase of autoimmune thyroiditis. M.5 cells did not express class II major histocompatibility complex encoded (Ia) antigens constitutively, but these could be readily induced with interferon-gamma. We found that Ia expressing M.5 cells were ineffective in stimulating T cell proliferation when tested in a 4-day primary mixed leukocyte reaction (MLR). However, significant T cell stimulation was obtained when phorbol myristate acetate (PMA) was added either to the M.5-T cell co-cultures, or for a brief period to the M.5 cells prior to adding the responder T cells. Cytofluorographic analysis of M.5 cells disclosed that PMA did not significantly alter the expression of Ia antigens. Additional experiments indicated that interleukin 1 (IL-1) was unlikely to represent the co-stimulatory factor generated by PMA. This was based on the observations that M.5 cells failed to secrete significant IL-1 either spontaneously, or in the presence of various stimuli, and that murine recombinant IL-1 failed to substitute for PMA in the activation of T cells. The nature of the co-stimulatory signal is as yet unknown. We conclude from these experiments that a pure population of thyroid-derived epithelial cells may be able to function, under the described circumstances, as antigen presenting cells.</jats:p