Schistosomiasis In School-aged Children Research Articles

Prevalence and factors associated with transmission of schistosomiasis in school-aged children in South Sudan: a cross-sectional study.

IntroductionSouth Sudan is affected by a high burden of Neglected Tropical Diseases (NTDs). The country is very vulnerable to NTDs due to its favourable tropical climate and multiple risk factors. However, the distribution of the diseases and the populations at risk for the various NTDs is unknown. This paper described the distribution of schistosomiasis in 58 counties and 261 schools in South Sudan.Methodsa descriptive quantitative cross-sectional study of schistosomiasis in 58 counties in 8 states of South Sudan recruited school-aged children. Using different laboratory techniques, the children were tested for Schistosoma mansoni (S. mansoni) and Schistosoma haematobium (S. haematobium). A quantitative descriptive statistical was performed to determine the prevalence rates and the endemicity of schistosomiasis among 13,286 school-aged children.Resultsthe overall prevalence of S. mansoni and S. haematobium were 6.1% and 3.7% using Kato Katz and urine filtration concentration testing techniques. The highest state prevalence was reported in Western Equatoria for both S. mansoni (14.7%) and S. haematobium (7.3%). The age of the participants varied from 4 to 18 years; of these, children 10 to 12 years old had the highest prevalence of S. mansoni (6.8%) and S. haematobium (3.7%). The prevalence of S. mansoni (7% male vs 5% female) and S. haematobium (3.6% male vs 3.1% female) were higher in males than females. The likelihood of the prevalence of S. mansoni in males was 1.42 (95% CI:1.23, 1.64) higher than in females, while for S. haematobium, 1.36 (95% CI:1.12, 1.65) higher than in females. The prevalence of S. mansoni and S. haematobium showed a statistically significant gender difference (P< 0.05).Conclusionthe study had provided evidence of the distribution of schistosomiasis in South Sudan for policy direction and recommended annual preventive chemotherapy with praziquantel in all endemic areas.

Prevalence of soil-transmitted helminth infections, schistosomiasis, and lymphatic filariasis before and after preventive chemotherapy initiation in the Philippines: A systematic review and meta-analysis

ObjectiveTo estimate the impact of preventive chemotherapy on the prevalence and intensity of soil-transmitted helminth (STH) infections, schistosomiasis, and lymphatic filariasis in the Philippines, using systematic review and meta-analysis.MethodsWe included reports reporting prevalence of STH infections, schistosomiasis, or lymphatic filariasis in the Philippines published until 31 March 2021. Peer-reviewed studies were identified in electronic databases. Grey literature reports by the University of the Philippines and the Department of Health were also included. Pooled infection prevalence, before and after the initiation of preventive chemotherapy, stratified by age group, was calculated using the inverse variance heterogeneity model.FindingsA total of 109 reports were included in the review and meta-analysis. Overall prevalence of moderate-heavy intensity Ascaris lumbricoides (6.6%) and Trichuris trichiura (2.7%) infection after initiation of preventive chemotherapy were significantly lower than the prevalence prior to initiation (23.6% for A. lumbricoides and 12.2% for T. trichiura). Prevalence reductions were also found in school and preschool-age children for A. lumbricoides and T. trichiura. Studies conducted after preventive chemotherapy initiation had significantly lower overall prevalence of moderate-heavy intensity schistosomiasis (3.1% vs 0.2%) and of schistosomiasis in school-age children (30.5% vs 1%). Pooled prevalence of lymphatic filariasis prior to preventive chemotherapy initiation was 3.2% across 12 provinces, while currently only two provinces still have prevalence of more than 1%. There were no published studies reporting prevalence of lymphatic filariasis after initiation of preventive chemotherapy. Heterogeneity was high with I2 mostly above 90%.ConclusionThe burden of STH infections and schistosomiasis in children were significantly lower in studies conducted following the initiation of preventive chemotherapy. Eliminating morbidity and interrupting transmission, however, may require expanded control initiatives including community-wide treatment, and improved water, sanitation, and hygiene. Lymphatic filariasis burden has decreased since the implementation of preventive chemotherapy, with all but two provinces having reached the elimination of lymphatic filariasis as a public health problem.

A 12-year follow-up of intestinal schistosomiasis in pre-school-aged children in Assoni Village, Eastern Senegal

BackgroundTo monitor the prevalence of schistosomiasis in school-aged children (SAC), the National Bilharzia Control Program (PNLB) was set up by the Senegalese authorities; however, geographically isolated Bedik ethnic groups that did not benefit from this program were found to be heavily infected with Schistosoma mansoni. This observation led us to implement a new schistosomiasis control program in 2008 under the aegis of the non-governmental organization “Le Kaïcedrat” and in partnership with the PNLB/WHO to monitor the prevalence of schistosomiasis in this area. In the village of Assoni, where 100% of SAC were infected, analysis of the stools of pre-school-aged children (PSAC) showed that they were massively infected, so we decided to focus our program on them.MethodsFrom 2008 to 2020, we (i) monitored the prevalence of S. mansoni in PSAC in Assoni using double-stool smear preparation, (ii) treated the infected PSAC with a standard dose of praziquantel 40 mg/kg, (iii) ran educational campaigns each year in the village, and (iv) built latrines to improve sanitation and reduce schistosomiasis transmission. Linear regression was used to examine the trend in the annual schistosomiasis prevalence and a two-sided of Chi-squared test was used to compare prevalence between the different age groups of PSAC.ResultsWe observed an extremely high prevalence of schistosomiasis (78%) in PSAC before implementation of the program in 2008. Contamination occurred in very young children, as 64.3% of children under 2 years old were infected. Moreover, prevalence increased with age and reached 96.8% in children 4 to < 6 years old. Our annual interventions in Assoni Village raised awareness among villagers that water bodies were areas of significant infestation, allowed the building of 88 latrines and led to a decrease in prevalence in PSAC as only 11% of these children were infected in 2020.ConclusionOur study allowed Assoni to be the first village in Senegal to treat PSAC since 2014, but only on an individual basis. It also shows that schistosomiasis is difficult to eradicate and that multi-sectorial actions are required to keep its prevalence at a low level.Graphic abstract

Retraction Note: The epidemiology and chemotherapeutic approaches to the control of urinary schistosomiasis in school-age children (SAC): a systematic review

The authors have retracted this article [1] because of methodological inaccuracies and incorrect use of the PRISMA/PROSPERO guidelines of systematic reviews and meta-analyses in the article.

Prevalence and Intensity of Urinary Schistosomiasis in School-age Children in Yewa North Local Government Area of Ogun State, Nigeria

The study was carried out to determine the prevalence rate of the schistosomiasis in school-aged children of 4 selected primary schools in Ijoun community of Yewa North Local Government Area in Ogun State and to evaluate the distribution of infection in terms of age and gender. A total number of 184 Urine samples were collected from the pupils and examined for the presence of over of Schistosoma haematobium, 89 0f the student were positive, Yewa North local Government School 1 had the highest prevalence with 58.82%, followed by Yewa North local Government School 2 with 50.0%, followed by Ansarudeen Primary School with 48%, and Yewa North local Government School 3 recorded the least with 40.0%. Out of 100 sample collected for male 49 were positive with the rate of 49.0% and 84 samples collected for female 40 were positive with the rate of 47.61%. The prevalence of schistosomiasis in relation to age groups. Age group 10 -12 years recorded the highest prevalence with 54.21% followed by age 7-9 with 52.38%, followed by age 13-15 with 37.73% and age group 16 -18 years had the lowest rate (33.33%). From the stated hypothesis, It can be affirmed that there is a significant difference between age and gender of the children in relation to schistosomiasis. There is a need for health education in the rural areas, designed to discourage the pupil's contact with surface water sources and provision of portable water supply.

Schistosomiasis in School Age Children in Sierra Leone After 6 Years of Mass Drug Administration With Praziquantel.

Historic data and baseline surveys showed schistosomiasis as highly/moderately endemic in 7 of 14 districts in Sierra Leone, justifying annual/biennial mass drug administration (MDA) with praziquantel. MDA commenced in 2009 and reported treatment coverage had been above the World Health Organization recommended 75% of target population. Assessment in 2012 showed significant reduction in infection. In 2016, another national school-based survey was conducted to evaluate the progress. Two schools from each category (high, moderate or low) of endemic communities in each MDA district and five schools in non-MDA districts were selected. Fifty children (25 boys and 25 girls) aged 9–14 years were randomly selected per school. Parasitological examination of 1,980 stool and 1,382 urine samples were conducted. Overall Schistosoma mansoni prevalence in the seven MDA districts decreased to 20.4% (95% CI: 18.7–22.3%) in 2016 from 42.2% (95% CI: 39.8–44.5%) at baseline (p < 0.0001). Mean overall S. mansoni intensity of infection reduced to 52.8 epg (95% CI: 43.2–62.4 epg) in 2016 from 100.5 epg (95% CI: 88.7–112.3 epg) at baseline (p < 0.001). The prevalence of Schistosoma haematobium in the five MDA districts that had baseline prevalence data decreased to 2.2% (95% CI: 1.5–3.1%) in 2016 from 18.3% (95% CI: 16.3–20.5%) at baseline (p < 0.0001). Mean overall intensity of infection increased to 1.12 e/10 ml (95% CI: 0.55–0.1.70 e/10 ml) in 2016 compared to 0.47 e/10 ml (95% CI: 0.16–0.78 e/10 ml) in 2012 (p < 0.05) (no baseline data). No district was highly endemic in 2016 compared to three at baseline and there was no significant difference in prevalence or intensity of infection by sex for both species. This survey illustrated the significant progress made in controlling schistosomiasis in Sierra Leone. The fact that prevalence and intensity of infection showed an increase from the 2010 level suggested a detrimental effect of missing MDA due to the Ebola toward schistosomiasis control. The national program needs to continue the treatment and adopt a comprehensive approach including water, hygiene, and sanitation measures to achieve control and elimination of schistosomiasis.

RETRACTED ARTICLE: The epidemiology and chemotherapeutic approaches to the controlof urinary schistosomiasis in school-age children (SAC): a systematicreview

BackgroundHuman schistosomiases are acute and chronic infectious diseases ofpoverty. Currently, epidemiological data of urinary schistosomiasis (US) inschool-age children (SAC) and adults are often reported together making itdifficult to ascertain the true status of the disease. Based on this premise, weset out to carry out this review.MethodTo achieve this aim, we carried out a computer-aided search ofPubMed, Web of Science, Science Direct, African Journals OnLine (AJOL) and thedatabase of World Health Organization. However, the information obtained fromthese sources was supplemented with additional literatures from Mendeley,Research Gate, and Google.ResultsThe search yielded 183 literatures of which 93 full text research,review and online articles were deemed fit for inclusion. Our key findingsshowed that: (1) of all World Health Organization (WHO) Regions, Africa is themost endemic zone for US, with Kenya and Senegal recording the highestprevalence and mean intensity respectively; (2) SAC within the range of5–16 years contribute most significantly to the transmission cycle of USglobally; (3) gender is a factor to watch out for, with male often recording thehighest prevalence and intensity of infection; (4) contact with open,potentially infested water sources contribute significantly to transmission; (5)parental factors (occupation and education status) predispose SAC to US; (6)economic vis a vis ecological factors play akey role in infection transmission; and (7) in the last decade, a treatmentcoverage of 45% was never achieved globally for SAC or non-SAC treatmentcategory for urinary schistosomiasis.ConclusionIn view of the WHO strategic plan to eliminate schistosomiasis by2020 and the findings from this review, it is obvious that this goal, in theface of realities, might not be achieved. It is imperative that annual controlprogrammes be scaled up marginally, particularly in the African region of WHO.While US-based researches should be sponsored at the grass-root level to unveilhidden endemic foci, adequate facilities for Water, Sanitation, and Hygiene(WASH) should be put in place in all schools globally.

Urinary schistosomiasis in school aged children of two rural endemic communities in Edo State, Nigeria.

Urinary schistosomiasis is endemic in many rural communities of Nigeria and school aged children are mostly affected. A cross-sectional study was carried out to assess the prevalence and intensity of urinary schistosomiasis infection among 251 school aged children in two communities of Ovia South West LGA of Edo State, Nigeria, as well as their knowledge on the control/elimination measures. Urine samples were collected and examined by microscopy using filtration technique. In addition, a questionnaire survey was conducted among school-aged children and health care providers, probing their knowledge, attitude and practices on on-going control activities. The prevalence of urinary schistosomiasis among the school-aged children was 65.3%. The prevalence was generally higher among females (68.8%) and children in the age groups 10-14 (69.9%). The intensity of infection ranged from 1 to 5044 (mean=449.8) eggs/10ml of urine with a higher proportion having heavy infections (76.8%, P<0.05). Water contact was attested by 123 (49.0%) of the children; of these 123, 74 (60.1%) were infected. The children's knowledge on urinary schistosomiasis was deficient. The high prevalences reported in these communities require integrated approach to control which essentially should incorporate the provision of safe water supply and sanitary facilities, and health education in addition to the annual mass praziquantel distribution, to reduce transmission.

High burden of Schistosoma mansoni infection in school-aged children in Marolambo District, Madagascar

BackgroundA school-based survey was undertaken to assess prevalence and infection intensity of schistosomiasis in school-aged children in the Marolambo District of Madagascar.MethodsSchool-aged children from six purposively selected schools were tested for Schistosoma haematobium by urine filtration and Schistosoma mansoni using circulating cathodic antigen (CCA) and Kato-Katz stool analysis. The investigators did not address soil-transmitted helminths (STH) in this study.ResultsOf 399 school-aged children screened, 93.7% were infected with S. mansoni based on CCA analysis. Kato-Katz analysis of stool revealed S. mansoni infection in 73.6% (215/ 292). Heavy infections (> 400 eggs per gram) were common (32.1%; 69/ 215), with a mean of 482 eggs per gram of stool. Moderate infection intensities were detected in 31.2% (67/ 215) and light infection intensities in 36.7% (79/ 215) of infected participants. No infection with S. haematobium was detected by urine filtration.ConclusionsIntestinal schistosomiasis appears a considerable public health issue in this remote area of Madagascar where there is a pressing need for mass drug administration.

Effect of National Schistosomiasis Control Programme on Taenia solium taeniosis and porcine cysticercosis in rural communities of Tanzania

Taenia solium is found throughout sub-Saharan Africa and co-endemic with schistosomiasis in many regions. Taenia solium leads to taeniosis and neurocysticercosis - the leading cause of preventable epilepsy globally. This study aimed to assess the effects of the National Schistosomiasis Control Programme on prevalence of taeniosis and porcine cysticercosis over a four year period in Tanzania. School-based mass drug administration (MDA) of praziquantel was carried out based on schistosomiasis endemicity. Four human and five porcine cross-sectional surveys were carried out from 2012 to 2015 in Mbozi and Mbeya district in Tanzania. Three rounds of school-based MDA of praziquantel were delivered in Mbozi and two in Mbeya. The prevalence of taeniosis and porcine cysticercosis was estimated annually. Stool samples were collected from humans and prevalence of taeniosis estimated by copro-Ag-ELISA. Blood samples from pigs were collected to estimate cysticercosis prevalence by Ag-ELISA. “Track-and-treat” of taeniosis cases was carried out after each survey. In total 12082 stool samples and 4579 porcine serum samples were collected. Significantly fewer children (≤15) from Mbozi were infected throughout the study than children from Mbeya who showed a significant decrease in copro-Ag prevalence after the first treatment only. During the final survey in Mbozi the prevalence of taeniosis in adults (1.8%) was significantly lower (p=0.031, OR 0.40, CI: 0.17–0.89), compared to baseline (4.1%). The prevalence of porcine cysticercosis (8%) had also dropped significantly (p=0.002, OR 0.49, CI: 0.32–0.76) in this district compared to baseline (13%), whereas no significant difference was seen in Mbeya compared to baseline. The study suggests that three rounds of MDA targeting schistosomiasis in school-aged children combined with ‘track-and-treat’ contributed to a reduction in prevalence of T. solium in this population, and also had a spillover effect on adults in treated areas as well as reducing the prevalence of T. solium in the intermediate pig host population. Elimination of T. solium in this area would require a One Health approach.

Spatial distribution of schistosomiasis and treatment needs in sub-Saharan Africa: a systematic review and geostatistical analysis

Schistosomiasis affects more than 200 million individuals, mostly in sub-Saharan Africa, but empirical estimates of the disease burden in this region are unavailable. We used geostatistical modelling to produce high-resolution risk estimates of infection with Schistosoma spp and of the number of doses of praziquantel treatment needed to prevent morbidity at different administrative levels in 44 countries. We did a systematic review to identify surveys including schistosomiasis prevalence data in sub-Saharan Africa via PubMed, ISI Web of Science, and African Journals Online, from inception to May 2, 2014, with no restriction of language, survey date, or study design. We used Bayesian geostatistical meta-analysis and rigorous variable selection to predict infection risk over a grid of 1 155 818 pixels at 5 × 5 km, on the basis of environmental and socioeconomic predictors and to calculate the number of doses of praziquantel needed for prevention of morbidity. The literature search identified Schistosoma haematobium and Schistosoma mansoni surveys done in, respectively, 9318 and 9140 unique locations. Infection risk decreased from 2000 onwards, yet estimates suggest that 163 million (95% Bayesian credible interval [CrI] 155 million to 172 million; 18·5%, 17·6-19·5) of the sub-Saharan African population was infected in 2012. Mozambique had the highest prevalence of schistosomiasis in school-aged children (52·8%, 95% CrI 48·7-57·8). Low-risk countries (prevalence among school-aged children lower than 10%) included Burundi, Equatorial Guinea, Eritrea, and Rwanda. The numbers of doses of praziquantel needed per year were estimated to be 123 million (95% CrI 121 million to 125 million) for school-aged children and 247 million (239 million to 256 million) for the entire population. Our results will inform policy makers about the number of treatments needed at different levels and will guide the spatial targeting of schistosomiasis control interventions. European Research Council, China Scholarship Council, UBS Optimus Foundation, and Swiss National Science Foundation.

Assessing the WHO 50% Prevalence Threshold in School-Aged Children as Indication for Treatment of Urogenital Schistosomiasis in Adults in Central Nigeria

Preventive chemotherapy with praziquantel is recommended in adults by the World Health Organization when prevalence of schistosomiasis in school-aged children (SAC) is ≥ 50%. This study ascertained the value of this threshold in predicting prevalence and intensity of Schistosoma hematobium (SH) infection in adults in central Nigeria. We evaluated urogenital schistosomiasis prevalence in 1,164 adults: 659 adults in 12 communities where mean hematuria among SAC in 2008 was 26.6% and 505 adults in 7 communities where the mean hematuria among SAC in 2008 was 70.4%. No statistically significant differences were found between the two groups of adults in prevalence of hematuria, prevalence of SH eggs, or intensity of infections. We conclude that, in this setting, the SAC threshold is not useful for treatment decisions in adults. Given the increased risk of subtle morbidity or urogenital schistosomiasis as a risk factor for human immunodeficiency virus (HIV), more liberal treatment of adults with praziquantel is warranted.

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.

Epidemiology and control of intestinal schistosomiasis on the Sesse Islands, Uganda: integrating malacology and parasitology to tailor local treatment recommendations

BackgroundIntestinal schistosomiasis is often widespread among the populations living around Lake Victoria and on its islands. The Sesse Island group (containing some 84 islands), however, is typically assumed to be a low prevalence zone, with limited transmission, but has never been surveyed in detail. Here, we present a rapid mapping assessment, bringing together snail and parasite information, at 23 sites for the presence of intermediate host snails and at 61 sites for the prevalence of intestinal schistosomiasis in school-aged children (N = 905). Two different diagnostic tools were used and compared at 45 of these sites: Kato-Katz thick faecal smears and circulating cathodic antigen (CCA) urine dipsticks.ResultsBiomphalaria snails were found at 11 sites but in low numbers; none was found shedding schistosome cercariae. At 22 out of the 45 sites, local prevalence by urine and/or stool diagnostics was in excess of 50%, although mean prevalence of intestinal schistosomiasis overall was 34.6% (95% confidence intervals (CI) = 31.0-38.3%) by Kato-Katz and 46.5% (95% CI = 42.7-50.4%) by CCA if 'trace' reactions were considered infection-positive (if considered infection-negative, mean prevalence was 28.1% (95% CI = 24.7-31.7%)). Diagnostic congruence between CCA and Kato-Katz was poor and significant discordance in estimated prevalence by location was found, with each often inferring different mass drug administration regimes.ConclusionsAccurate estimation of schistosome prevalence is important for determining present and future treatment needs with praziquantel; the wide range of schistosome prevalence across the Sesse Island group requires a treatment regime largely tailored to each island. In high prevalence locations, further malacological sampling is required to confirm the extent of local transmission, especially on the northern islands within the group. The observation that different diagnostic tests can provide varying results in terms of estimating prevalence by location, and hence change treatment recommendations, suggests that care must be taken in interpreting raw prevalence data. In particular, further research into the reasons for the differences in the poorer performance of the CCA test should be pursued.

Soil transmitted helminth infections and schistosomiasis in school age children in sub-Saharan Africa: Efficacy of chemotherapeutic intervention since World Health Assembly Resolution 2001

Soil transmitted helminth infections (STH) and schistosomiasis constitute major public health challenges among school-age children in sub-Saharan Africa. This review assessed the efficacy of chemotherapeutic intervention in line with the World Health Assembly (WHA) resolution since the passage in 2001. Using the Medline Entrez-Pubmed search, relevant publications were identified via combinations of key words such as helminth infection, school children, chemotherapy, Africa. Albendazole, mebendazole, and praziquantel were the antihelminthic drugs most commonly evaluated. Cure rates >80% and egg reduction rates >90% were recorded in most cases of schistosomiasis using praziquantel. Albendazole was very effective against A. lumbricoides and hookworm infections with majority of the studies recording cure rates >75%, but the efficacy of the drug was poor against T. trichiura. To ensure the realization of the WHA resolution, there is need for regular treatment of school children, development of alternative antihelminthic drugs and vaccines, environmental control measures and health education.

The prevalence of schistosomiasis in school-aged children as an appropriate indicator of its prevalence in the community

School-aged children (6-15 years) from the endemic area of Pernambuco were evaluated both as a target group for and an indicator of schistosomiasis control in the community. Parasitological data were drawn from baseline stool surveys of whole populations that were obtained to diagnose Schistosoma mansoni infection. Nineteen representative localities were selected for assessing the prevalence of schistosomiasis among individuals in the following age groups: 0-5, 6-15, 16-25, 26-40 and 41-80 years. For each locality, the prevalence in each age group was compared to that of the overall population using contingency table analysis. To select a reference group, the operational difficulties of conducting residential surveys were considered. School-aged children may be considered to be the group of choice as the reference group for the overall population for the following reasons: (i) the prevalence of schistosomiasis in this age group had the highest correlation with the prevalence in the overall population (r = 0.967), (ii) this age group is particularly vulnerable to infection and plays an important role in parasite transmission and (iii) school-aged children are the main target of the World Health Organization in terms of helminth control. The Schistosomiasis Control Program should consider school-aged children both as a reference group for assessing the need for intervention at the community level and as a target group for integrated health care actions of the Unified Health System that are focused on high-risk groups.

Bayesian spatial analysis and disease mapping: tools to enhance planning and implementation of a schistosomiasis control programme in Tanzania

To predict the spatial distributions of Schistosoma haematobium and S. mansoni infections to assist planning the implementation of mass distribution of praziquantel as part of an on-going national control programme in Tanzania. Bayesian geostatistical models were developed using parasitological data from 143 schools. In the S. haematobium models, although land surface temperature and rainfall were significant predictors of prevalence, they became non-significant when spatial correlation was taken into account. In the S. mansoni models, distance to water bodies and annual minimum temperature were significant predictors, even when adjusting for spatial correlation. Spatial correlation occurred over greater distances for S. haematobium than for S. mansoni. Uncertainties in predictions were examined to identify areas requiring further data collection before programme implementation. Bayesian geostatistical analysis is a powerful and statistically robust tool for identifying high prevalence areas in a heterogeneous and imperfectly known environment.

Schistosomiasis in Lake Malawi: Relationship of Fish and Intermediate Host Density to Prevalence of Human Infection

Prior to 1985, the open waters of Lake Malawi were free from schistosome transmission. Over the past decades, however, the prevalence of urinary schistosomiasis has increased dramatically in the southern part of the lake. We found the prevalence of human schistosomiasis in school-aged children to be negatively correlated with the density of molluscivorous fishes. Specifically, the increased infection rate in southern Lake Malawi between 1978 and 1991 is coincident with the reduction in numbers of snail-eating fishes. During 2003, we determined the relative abundance of molluscivorous fishes and snail density at 18 sites throughout the lake and schistosome infection in school-aged children living in selected lakeshore communities of Lake Malawi. At the 18 sites sampled in 2003, we found that snail abundance decreased with an increase in abundance of snail-eating fishes. Furthermore, the 2003 samples showed that the abundance of snail-eating fishes increased and there was a reduction in schistosomiasis in school-aged children in Chembe Village. We believe that we will not observe a return to the 1978 infection rates until these fishes continue to increase and inhabit shallower waters.

Schistosomiasis mansoni in school attenders and non-attenders in Northwest Ethiopia

Background: Information on epidemiology of schistosomiasis in school age children and particularly non school attenders are scanty in northwestern Ethiopia. Objective: To assess the prevalence of Schistosoma mansoni in school attenders and non-attenders in Northwest Ethiopia. Methods: A parasitological survey was carried out from June 1995 - July 1997 in selected communities and schools. Results: Of the 199 community based school attenders in Zarima, 198 in Gorgora and 200 in Dek, 85%, 67% respectively were positive for S. mansoni. Of the non-attenders in Zarima, 60(50%) in Gorgora and 90(44%) in Dek were positive for S. mansoni. Among school attenders the intensity of infection (mean egg count) was fond to be 177 eggs per gram (epg), 139 epg, and 135 epg in Zarima, Gorgora and Dek respectively. Among non - attenders the intensity of infection was 166 epg, 100 epg, and 121 epg in Zarima, Gorgora, and Dek respectively. The study demonstrates that the infection rates and the intensities of infection of S. mansoni were higher in school attenders than in non-attenders. The difference in prevalence was statistically significant (P