Distribution Of Schistosomiasis Research Articles

Modelling the historical distribution of schistosomiasis-transmitting snails in South Africa using ecological niche models.

Schistosomiasis is a vector-borne disease transmitted by freshwater snails and is prevalent in rural areas with poor sanitation and no access to tap water. Three snail species are known to transmit schistosomiasis in South Africa (SA), namely Biomphalaria pfeifferi, Bulinus globosus and Bulinus africanus. In 2003, a predicted prevalence of 70% was reported in tropical climates in SA. Temperature and rainfall variability can alter schistosomiasis-transmitting snails' development by increasing or decreasing their abundance and geographical distribution. This study aimed to map the historical distribution of schistosomiasis from 1950 to 2006 in SA. The snail sampling data were obtained from the historical National Snail Freshwater Collection (NFSC). Bioclimatic variables were extracted using ERA 5 reanalysis data provided by the Copernicus Climate Change Service. In this study, we used 19 bioclimatic and four soil variables. The temporal aggregation was the mean climatological period pre-calculated over the 40-year reference period with a spatial resolution of 0.5° x 0.5°. Multicollinearity was reduced by calculating the Variance Inflation Factor Core (VIF), and highly correlated variables (> 0.85) were excluded. To obtain an "ensemble" and avoid the integration of weak models, we averaged predictions using the True Skill Statistical (TSS) method. Results showed that the ensemble model achieved the highest Area Under the Curve (AUC) scores (0.99). For B. africanus, precipitation-related variables contributed to determining the suitability for schistosomiasis. Temperature and precipitation-related variables influenced the distribution of B. globosus in all three models. Biomphalaria pfeifferi showed that Temperature Seasonality (bio4) contributed the most (47%) in all three models. According to the models, suitable areas for transmitting schistosomiasis were in the eastern regions of South Africa. Temperature and rainfall can impact the transmission and distribution of schistosomiasis in SA. The results will enable us to develop future projections for Schistosoma in SA based on climate scenarios.

The historic distribution of schistosomiasis transmitting snails in Mbombela and Nkomazi local municipalities

The historic distribution of schistosomiasis transmitting snails in Mbombela and Nkomazi local municipalities

Malacological Survey and Spatial Distribution of Intermediate Host Snails in Schistosomiasis Endemic Districts of Rwanda.

Schistosomiasis, due to S. mansoni, is prevalent in Rwanda. However, there is a paucity of information related to the abundance, species, distribution, and infectivity of Schistosoma intermediate host snails. Snails were collected from 71 sites, including lakeshores and wetlands. Snails obtained were morphologically identified, and cercariae were shed using standard procedures. Cercariae were molecularly characterized using PCR. GPS coordinates were used to generate geospatial maps of snail distribution that were overlaid with geospatial distribution of schistosomiasis among pre-school children in the same areas. Overall, 3653 snails were morphologically classified as Bulinus spp. and 1449 as Biomphalaria spp. A total of 306 snails shed cercariae, 130 of which were confirmed as S. mansoni cercaria by PCR. There was no significant difference in the proportion of S. mansoni cercariae in wetlands compared to lakeshores. Rwandan water bodies harbor an important number of snails that shed S. mansoni cercariae. Furthermore, a strong spatial correlation was observed between the distribution of schistosomiasis in children and the spatial distribution of snail infectivity with S. mansoni. The presence of Bulinus spp. Suggests a potential risk of S. haematobium, although molecular analysis did not show any current transmission of this parasite.

Spatiotemporal distribution of schistosomiasis transmission risk in Jiangling County, Hubei Province, P.R. China.

This study aims to explore the spatiotemporal distribution of schistosomiasis in Jiangling County, and provide insights into the precise schistosomiasis control. The descriptive epidemiological method and Joinpoint regression model were used to analyze the changes in infection rates of humans, livestock, snails, average density of living snails and occurrence rate of frames with snails in Jiangling County from 2005 to 2021. Spatial epidemiology methods were used to detect the spatiotemporal clustering of schistosomiasis transmission risk in Jiangling county. The infection rates in humans, livestock, snails, average density of living snails and occurrence rate of frames with snails in Jiangling County decreased from 2005 to 2021 with statistically significant. The average density of living snails in Jiangling County was spatially clustered in each year, and the Moran's I varied from 0.10 to 0.26. The hot spots were mainly concentrated in some villages of Xionghe Town, Baimasi Town and Shagang Town. The mean center of the distribution of average density of living snails in Jiangling County first moved from northwest to southeast, and then returned from southeast to northwest after 2014. SDE azimuth fluctuated in the range of 111.68°-124.42°. Kernal density analysis showed that the high and medium-high risk areas of Jiangling County from 2005 to 2021 were mainly concentrated in the central and eastern of Jiangling County, and the medium-low and low risk areas were mainly distributed in the periphery of Jiangling County. The epidemic situation of schistosomiasis decreased significantly in Jiangling County from 2005 to 2021, but the schistosomiasis transmission risk still had spatial clustering in some areas. After transmission interruption, targeted transmission risk intervention strategies can be adopted according to different types of schistosomiasis risk areas.

Prevalence and risk distribution of schistosomiasis among adults in Madagascar: a cross-sectional study

BackgroundThe goal to eliminate the parasitic disease of poverty schistosomiasis as a public health problem is aligned with the 2030 United Nations agenda for sustainable development goals, including universal health coverage (UHC). Current control strategies focus on school-aged children, systematically neglecting adults. We aimed at providing evidence for the need of shifting the paradigm of schistosomiasis control programs from targeted to generalized approaches as key element for both the elimination of schistosomiasis as a public health problem and the promotion of UHC.MethodsIn a cross-sectional study performed between March 2020 and January 2021 at three primary health care centers in Andina, Tsiroanomandidy and Ankazomborona in Madagascar, we determined prevalence and risk factors for schistosomiasis by a semi-quantitative PCR assay from specimens collected from 1482 adult participants. Univariable and multivariable logistic regression were performed to evaluate odd ratios.ResultsThe highest prevalence of S. mansoni, S. haematobium and co-infection of both species was 59.5%, 61.3% and 3.3%, in Andina and Ankazomborona respectively. Higher prevalence was observed among males (52.4%) and main contributors to the family income (68.1%). Not working as a farmer and higher age were found to be protective factors for infection.ConclusionsOur findings provide evidence that adults are a high-risk group for schistosomiasis. Our data suggests that, for ensuring basic health as a human right, current public health strategies for schistosomiasis prevention and control need to be re-addressed towards more context specific, holistic and integrated approaches.

Prevalence, Peculiarities and Patterns of Urogenital Schistosomiasis and Hematuria in Owena Reservoir Area, Ondo East Local Government Area, Ondo State, Nigeria

Background: Schistosomiasis, Leprosy, Leishmaniasis, Malaria, Trypanosomiasis and Filariasis are the six major tropical diseases, specially targeted for control by the Special Program for Research and Training on Tropical Diseases of the United Nations Development Programme (UNDP), World Bank and World Health Organization. Out of the above six diseases, schistosomiasis is the second most important tropical diseases, second only to malaria. The distribution of schistosomiasis cuts across 76 countries in Africa, Latin America and Asia. Schistosoma hematobium endemicity cuts across 54 countries. Aim: To study the prevalence, peculiarities and patterns of urogenital schistosomiasis and hematuria in Owena Reservoir Area for an effective, affordable and sustainable schistosomiasis control in the area. Materials and methods: Owena Reservoir Area consists of Owena, Kajola and Baiken communities. A school-based cross-sectional technique was used for urine collection and quantification of Schistosoma hematobium eggs which involved 624 pupils in March 2014 and 591 pupils in April 2015. Risk factors, socio-demographic variables were collected using questionnaires. Urine samples were examined for Schistosoma hematobium eggs using sedimentation by gravity cum centrifugation. The urine samples obtained from the pupils were divided into two separate 30ml universal sterling plastic bottles with conical bottom. The first of the two 30ml universal sterling plastic bottles were examined for Schistosoma hematobium eggs using sedimentation by gravity cum centrifugation. The second of the two 30ml universal sterling plastic bottles were assessed for gross hematuria through visual observation of bloody urine while non-bloody samples were examined for micro-hematuria using one strip of commercially prepared chemical reagent strips COMBUR-9 prepared and marketed by Acun Laboratory USA which was dipped into each urine sample and the color change was matched with standard by the side of the container of the reagent strips. Results: Out of the 624 pupils examined in March 2014, 256 (41.0%) were positive for Schistosoma hematobium eggs in urine, while in April 2015, 381 (64.5%) out of 591 were positive. Prevalence of hematuria in the three communities shows that in Owena community the age group 21 – 30 had the highest prevalence (49.2%); in Kajola, the age group 5-10 had the highest prevalence (46.2%); while in Baiken community, the age group 5-10 had the highest prevalence (55.5%) – with 95% Confidence Interval in all cases. Conclusion: Macrohematuria was identified as a sensitive and specific diagnostic technique for identifying people infected with Schistosoma hematobium in the three communities. This parameter may be recommended as a cost saving diagnostic approach during future control efforts, with reference to the April 2015 peculiarities and patterns of infection shown by this study.

Spatial Distribution of Schistosomiasis and itsassociated risk factors among Preschool aged children in Temeke district, Tanzania

Spatial Distribution of Schistosomiasis and itsassociated risk factors among Preschool aged children in Temeke district, Tanzania

Schistosomiasis control in adults: a call for action towards the goal of universal health coverage

Abstract Background Schistosomiasis is a high-burden parasitic disease and endemic in tropical climates, such as Madagascar. Recently it is emerging in Europe. Chronic infections lead to disabilities including loss in work productivity. Current control strategies focus on school-aged children, thereby systematically excluding adults. The goal to eliminate the disease as a public health problem is aligned with the Sustainable Development Goals agenda, including Universal Health Coverage (UHC). We aim at assessing the distribution of schistosomiasis among adults in Madagascar, in order to promote more targeted public health initiatives against the disease. Methods In a cross-sectional study, 1477 blood samples were collected at three primary health-care centers in Madagascar from 03.21 to 01.22. A semi quantitative PCR assay was used to assess the presence of Schistosoma. Positivity rates with 95% Confidence Intervals (CI) were reported by gender and age groups. Results Our study population had a balanced gender distribution with 54.2% [CI: 51.7;56.8] of females and a median age of 37 years (IQR: 24-48). Preliminary results show an overall Schistosome positivity rate of 59.5% [CI: 57.0;62.0]. Positivity was higher in males 62.4% [CI: 58.7;66.1], than in females 57.1% [CI: 53.5;60.5]. Highest positivity was seen in the 18-34 year age group with 66.2% [CI: 62.7;69.6]. Lowest positivity of 46.2% [CI: 39.2;53.2] was observed in adults aged over 55 years. Conclusions Our preliminary results provide evidence of high positivity rates of schistosomiasis among adults in a highly endemic country. Differently from many studies, males seem more affected than females. The youngest age group, representing the more active workforce of a population, shows a higher positivity rate. Our data suggests that, in the logic of UHC and health as a human right, public health strategies for schistosomiasis need to be re-addressed towards a universal coverage of affected individuals. Key messages

Spatial Analysis of Schistosomiasis in Hunan and Jiangxi Provinces in the People’s Republic of China

Understanding the spatial distribution of schistosome infection is critical for tailoring preventive measures to control and eliminate schistosomiasis. This study used spatial analysis to determine risk factors that may impact Schistosoma japonicum infection and predict risk in Hunan and Jiangxi Provinces in the People’s Republic of China. The study employed survey data collected in Hunan and Jiangxi in 2016. Independent variable data were obtained from publicly available sources. Bayesian-based geostatistics was used to build models with covariate fixed effects and spatial random effects to identify factors associated with the spatial distribution of infection. Prevalence of schistosomiasis was higher in Hunan (12.8%) than Jiangxi (2.6%). Spatial distribution of schistosomiasis varied at pixel level (0.1 × 0.1 km), and was significantly associated with distance to nearest waterbody (km, β = −1.158; 95% credible interval [CrI]: −2.104, −0.116) in Hunan and temperature (°C, β = −4.359; 95% CrI: −9.641, −0.055) in Jiangxi. The spatial distribution of schistosomiasis in Hunan and Jiangxi varied substantially and was significantly associated with distance to nearest waterbody. Prevalence of schistosomiasis decreased with increasing distance to nearest waterbody in Hunan, indicating that schistosomiasis control should target individuals in close proximity to open water sources as they are at highest risk of infection.

Schistosoma mansoni Epidemiology Among Snails, Rodents and Children: A One Health Approach.

BackgroundSchistosoma is one of the prevalent parasitic infection in humans and animals. Schistosomiasis in children is particularly serious and results in liver and spleen enlargement, anemia, stunting, reduced ability to learn and death. The aim of this study was to measure the prevalence and distribution of schistosomiasis in children, rodents and snail populations in Aleffa and Takusa districts, north-west Ethiopia.MethodsDisease status and exposure were simultaneously measured from December 2020 to December 2021. School children's stool specimens were collected for schistosomiasis examination by Kato Katz and formal-ether techniques. Live rodents and snails were trapped and collected in search of adult schistosoma, eggs, and cercariae, respectively. Multiple logistic regression analytic technique by using SPSS version 20 was conducted.ResultsOf 460 stool specimens examined, 116 (25.22) were found positive for S. mansoni infection. In the present finding, the possible determinants for the occurrence of intestinal schistosomiasis in school children were female sex (AOR = 1.09, 95% CI: 1.37–2.96); working with bare foot (AOR = 1.21, 95% CI: 1.08–1.52); skin cut/abrasion history (AOR = 3.6, 95% CI: 1.08–7.43) and swimming habit (AOR = 1.58, 95% CI: 1.33–1.99). The overall (n = 108) rodent prevalence of S. mansoniwas 23 (21.3%). Only 6 snails were shedding the infective stage of schistosoma cercariae.ConclusionThe study revealed that there is a moderate prevalence of schistosomiasis in different hosts. Thus, multi-host intervention is crucial to achieving the goal of interrupting transmission of schistosomiasis in the study area. Further research to better understand and exploit the broader environmental, ecological context and encompassing dynamic interactions between all hosts over time will be crucial for building predictive models beyond the known fact of having or not having reservoirs/hybridization of schistosoma in our study area.

Schistosoma mansoni and soil-transmitted helminths among schoolchildren in An-Nadirah District, Ibb Governorate, Yemen after a decade of preventive chemotherapy.

The Ministry of Public Health in Yemen continues the implementation of school and community–based preventive chemotherapy with praziquantel and albendazole for the control and elimination of schistosomiasis and soil-transmitted helminths (STH). The latest remapping to update the distribution of schistosomiasis and STH was conducted seven years ago. This study aimed to estimate the prevalence, intensity and associated risk factors of Schistosoma mansoni and STH among schoolchildren in An-Nadirah District, Ibb Governorate, Yemen. A cross-sectional study was carried out among schoolchildren aged 6–15 years in four selected schools. Biological, demographic, socioeconomic and environmental data were collected using a pre-tested questionnaire. S. mansoni and STH eggs were detected and counted by the microscopic examination of Kato-Katz fecal smears. Out of 417 schoolchildren, 17.0% were infected with at least one intestinal helminth. Prevalence of S. mansoni and STH were 6.5% and 9.1%, respectively. The most prevalent parasite among STH was Ascaris lumbricoides (8.4%). Unemployed fathers (Adjusted Odds Ratio (AOR) = 3.2; 95% Confidence interval (CI): 1.23, 8.52; P = 0.018), eating exposed food (AOR: 2.9; 95%CI = 1.24, 6.89; P = 0.014), not washing hands before eating and after defecation (AOR: 4.8; 95%CI = 1.77, 12.81; P = 0.002), and schools located close to water stream (AOR: 22.1; 95%CI = 5.12, 95.46; P <0.001) were independent risk factors of ascariasis. Swimming in ponds/stream (AOR: 3.9; 95%CI = 1.63, 9.55; P = 0.002), and schools close to the stream (AOR: 24.7; 95%CI = 3.05, 200.07; P = 0.003) were independent risk factors of intestinal schistosomiasis. The present study does not indicate a reduction in the prevalence of intestinal schistosomiasis in this rural area since the latest remapping conducted in 2014, although ascariasis was reduced by half. The prevalence of the two parasites was highly focal in areas close to the valley, suggesting a significant role of the stream in sustaining and accelerating the parasitic infection. Children practicing swimming and having poor hygienic practices were at high exposure to S. mansoni and A. lumbricoides, respectively. Water, Sanitation and Hygiene intervention, school–based health education, and snail control, in addition to mass drug administration, will help in the interruption of transmission of schistosomiasis and STH.

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.

Spatiotemporal heterogeneity of schistosomiasis in mainland China: Evidence from a multi-stage continuous downscaling sentinel monitoring

Objective: To determine the spatiotemporal distribution of Schistosoma (S.) japonicum infections in humans, livestock, and Oncomelania (O.) hupensis across the endemic foci of China.Methods: Based on multi-stage continuous downscaling of sentinel monitoring, county-based schistosomiasis surveillance data were captured from the national schistosomiasis surveillance sites of China from 2005 to 2019. The data included S. japonicum infections in humans, livestock, and O. hupensis. The spatiotemporal trends for schistosomiasis were detected using a Joinpoint regression model, with a standard deviational ellipse (SDE) tool, which determined the central tendency and dispersion in the spatial distribution of schistosomiasis. Further, more spatiotemporal clusters of S. japonicum infections in humans, livestock, and O. hupensis were evaluated by the Poisson model.Results: The prevalence of S. japonicum human infections decreased from 2.06% to zero based on data of the national schistosomiasis surveillance sites of China from 2005 to 2019, with a reduction from 9.42% to zero for the prevalence of S. japonicum infections in livestock, and from 0.26% to zero for the prevalence of S. japonicum infections in O. hupensis. Analysis using an SDE tool showed that schistosomiasis-affected regions were reduced yearly from 2005 to 2014 in the endemic provinces of Hunan, Hubei, Jiangxi, and Anhui, as well as in the Poyang and Dongting Lake regions. Poisson model revealed 11 clusters of S. japonicum human infections, six clusters of S. japonicum infections in livestock, and nine clusters of S. japonicum infections in O. hupensis. The clusters of human infection were highly consistent with clusters of S. japonicum infections in livestock and O. hupensis. They were in the 5 provinces of Hunan, Hubei, Jiangxi, Anhui, and Jiangsu, as well as along the middle and lower reaches of the Yangtze River. Humans, livestock, and O. hupensis infections with S. japonicum were mainly concentrated in the north of the Hunan Province, south of the Hubei Province, north of the Jiangxi Province, and southwestern portion of Anhui Province. In the 2 mountainous provinces of Sichuan and Yunnan, human, livestock, and O. hupensis infections with S. japonicum were mainly concentrated in the northwestern portion of the Yunnan Province, the Daliangshan area in the south of Sichuan Province, and the hilly regions in the middle of Sichuan Province.Conclusions: A remarkable decline in the disease prevalence of S. japonicum infection was observed in endemic schistosomiasis in China between 2005 and 2019. However, there remains a long-term risk of transmission in local areas, with the highest-risk areas primarily in Poyang Lake and Dongting Lake regions, requiring to focus on vigilance against the rebound of the epidemic. Development of high-sensitivity detection methods and integrating the transmission links such as human and livestock infection, wild animal infection, and O. hupensis into the surveillance-response system will ensure the elimination of schistosomiasis in China by 2030.

Infestation risk of the intermediate snail host of Schistosoma japonicum in the Yangtze River Basin: improved results by spatial reassessment and a random forest approach

BackgroundOncomelania hupensis is only intermediate snail host of Schistosoma japonicum, and distribution of O. hupensis is an important indicator for the surveillance of schistosomiasis. This study explored the feasibility of a random forest algorithm weighted by spatial distance for risk prediction of schistosomiasis distribution in the Yangtze River Basin in China, with the aim to produce an improved precision reference for the national schistosomiasis control programme by reducing the number of snail survey sites without losing predictive accuracy.MethodsThe snail presence and absence records were collected from Anhui, Hunan, Hubei, Jiangxi and Jiangsu provinces in 2018. A machine learning of random forest algorithm based on a set of environmental and climatic variables was developed to predict the breeding sites of the O. hupensis intermediated snail host of S. japonicum. Different spatial sizes of a hexagonal grid system were compared to estimate the need for required snail sampling sites. The predictive accuracy related to geographic distances between snail sampling sites was estimated by calculating Kappa and the area under the curve (AUC).ResultsThe highest accuracy (AUC = 0.889 and Kappa = 0.618) was achieved at the 5 km distance weight. The five factors with the strongest correlation to O. hupensis infestation probability were: (1) distance to lake (48.9%), (2) distance to river (36.6%), (3) isothermality (29.5%), (4) mean daily difference in temperature (28.1%), and (5) altitude (26.0%). The risk map showed that areas characterized by snail infestation were mainly located along the Yangtze River, with the highest probability in the dividing, slow-flowing river arms in the middle and lower reaches of the Yangtze River in Anhui, followed by areas near the shores of China’s two main lakes, the Dongting Lake in Hunan and Hubei and the Poyang Lake in Jiangxi.ConclusionsApplying the machine learning of random forest algorithm made it feasible to precisely predict snail infestation probability, an approach that could improve the sensitivity of the Chinese schistosome surveillance system. Redesign of the snail surveillance system by spatial bias correction of O. hupensis infestation in the Yangtze River Basin to reduce the number of sites required to investigate from 2369 to 1747.Graphical abstract

Prevalence, infection intensity and geographical distribution of schistosomiasis among pre-school and school aged children in villages surrounding Lake Nyasa, Tanzania

Planning and implementation of schistosomiasis control activities requires an understanding of the prevalence, intensity of infection and geographical distribution of the disease in different epidemiological settings. Although, Tanzania is known to be highly endemic to schistosomiasis, there is paucity of data on the geographical distribution of schistosomiasis in potential large water bodies in the country. Thus, the present study was conducted to determine the prevalence, infection intensities and geographical distribution of schistosomiasis along villages located on the shoreline of Lake Nyasa, southern Tanzania. A cross-sectional study was conducted among 1560 children aged 1–13 years old living in villages located along the shoreline of Lake Nyasa. A single urine and stool sample was obtained from each participating child and screened for S.mansoni using Kato Katz (KK) technique to detect eggs and using point-of-care circulating Cathodic Antigen (POC-CCA) test to detect antigen in urine. Urine filtration technique was used to screen for S.haematobium eggs in urine samples. Villages/primary school were mapped using geographical information system and prevalence map was generated using ArcView GIS software. The overall prevalence of S.mansoni based on KK technique and POC-CCA test was 15.1% (95%CI: 13.4–16.9) and 21.8% (95%CI: 18.5–25.3) respectively. The prevalence S.haematobium was 0.83% (95%CI: 0.5–1.4) and that of haematuria was 0.9%. The arithmetic mean egg intensities for S.haematobium and S.mansoni were 18.5 mean eggs/10 ml (95%CI: 5.9–57.6) of urine and 34.7 mean epg (95%CI: 27.7–41.7) respectively. Villages located on the southern end of the lake had significantly high prevalence of S.mansoni than those located on the northern part (χ2 = 178.7838, P = 0.001). Cases of S.haematobium were detected only in three villages. Both S.mansoni and S.haematobium infections occur in villages located along the shoreline of Lake Nyasa at varying prevalence. These finding provide insights that can provide guidance in planning and implementation of MDA approach and other recommended measures such as improvement in sanitation, provision of clean water and behaviour changes through public health education.

Dynamic evolution of schistosomiasis distribution under different control strategies: Results from surveillance covering 1991-2014 in Guichi, China.

BackgroundSince the founding of the China, the Chinese government, depending on the changing epidemiological situations over time, adopted different strategies to continue the progress towards elimination of schistosomiasis in the country. Although the changing pattern of schistosomiasis distribution in both time and space is well known and has been confirmed by numerous studies, the problem of how these patterns evolve under different control strategies is far from being understood. The purpose of this study is, therefore, to investigate the spatio-temporal change of the distribution of schistosomiasis with special reference to how these patterns evolve under different control strategies.Methodology / Principal findingsParasitological data at the village level were obtained through access to repeated cross-sectional surveys carried out during 1991–2014 in Guichi, a rural district along the Yangtze River in Anhui Province, China. A hierarchical dynamic spatio-temporal model was used to evaluate the evolving pattern of schistosomiasis prevalence, which accounted for mechanism of dynamics of the disease. Descriptive analysis indicates that schistosomiasis prevalence displayed fluctuating high-risk foci during implementation of the chemotherapy-based strategy (1991–2005), while it took on a homogenous pattern of decreasing magnitude in the following period when the integrated strategy was implemented (2006–2014). The dynamic model analysis showed that regularly global propagation of the disease was not present after the effect of proximity to river was taken into account but local pattern transition existed. Maps of predicted prevalence shows that relatively high prevalence (>4%) occasionally occurred before 2006 and prevalence presents a homogenous and decreasing trend over the study area afterwards.ConclusionsProximity to river is still an important determinant for schistosomiasis infection regardless of different types of implemented prevention and control strategies. Between the transition from the chemotherapy-based strategy to the integrated one, we noticed a decreased prevalence. However, schistosomiasis would remain an endemic challenge in these study areas. Further prevention and control countermeasures are warranted.

Analisis Kestabilan Model Matematika Penyebaran Penyakit Schistosomiasis dengan Saturated Incidence Rate

Schistosomiasis is a disease caused by infections of the genus Schistosoma. Schistosomiasis can be transmitted through schistosoma worms that contact human skin. Schistosomiasis is a disease that continues to increase in spread. Saturated incidence rates pay attention to the ability to infect a disease that is limited by an increase in the infected population. This thesis formulates and analyzes a mathematical model of the distribution of schistosomiasis with a saturated incidence rate. Based on the analysis of the model, two equilibrium points are obtained, namely non-endemic equilibrium points (E0) and endemic equilibrium points (E1). Both equilibrium points are conditional asymptotically stable. The nonendemic equilibrium point will be asymptotically stable if rh &gt; dh, rs &gt; ds and R0 &lt; 1, while the endemic equilibrium point will be asymptotically stable if R0 &gt; 1. Sensitivity analysis shows that there are parameters that affect the spread of the disease. Based on numerical simulation results show that when R0 &lt; 1, the number of infected human populations (Hi), the number of infected snail populations (Si), the amount of cercaria density (C) and the amount of miracidia density (M) will tend to decrease until finally extinct. Otherwise at the time R0 &gt; 1, the number of the four populations tends to increase before finally being in a constant state.

Evaluating survey designs for targeting preventive chemotherapy against Schistosoma haematobium and Schistosoma mansoni across sub-Saharan Africa: a geostatistical analysis and modelling study

BackgroundSchistosomiasis control programmes primarily use school-based surveys to identify areas for mass drug administration of preventive chemotherapy. However, as the spatial distribution of schistosomiasis can be highly focal, transmission may not be detected by surveys implemented at districts or larger spatial units. Improved mapping strategies are required to accurately and cost-effectively target preventive chemotherapy to remaining foci across all possible spatial distributions of schistosomiasis.MethodsHere, we use geostatistical models to quantify the spatial heterogeneity of Schistosoma haematobium and S. mansoni across sub-Saharan Africa using the most comprehensive dataset available on school-based surveys. Applying this information to parameterise simulations, we assess the accuracy and cost of targeting alternative implementation unit sizes across the range of plausible schistosomiasis distributions. We evaluate the consequences of decisions based on survey designs implemented at district and subdistrict levels sampling different numbers of schools. Cost data were obtained from field surveys conducted across multiple countries and years, with cost effectiveness evaluated as the cost per correctly identified school.ResultsModels identified marked differences in prevalence and spatial distributions between countries and species; however, results suggest implementing surveys at subdistrict level increase the accuracy of treatment classifications across most scenarios. While sampling intensively at the subdistrict level resulted in the highest classification accuracy, this sampling strategy resulted in the highest costs. Alternatively, sampling the same numbers of schools currently recommended at the district level but stratifying by subdistrict increased cost effectiveness.ConclusionsThis study provides a new tool to evaluate schistosomiasis survey designs across a range of transmission settings. Results highlight the importance of considering spatial structure when designing sampling strategies, illustrating that a substantial proportion of children may be undertreated even when an implementation unit is correctly classified. Control programmes need to weigh the increased accuracy of more detailed mapping strategies against the survey costs and treatment priorities.Graphical

Prevalence and distribution of schistosomiasis in human, livestock, and snail populations in northern Senegal: a One Health epidemiological study of a multi-host system

SummaryBackgroundSchistosomiasis is a neglected tropical disease of global medical and veterinary importance. As efforts to eliminate schistosomiasis as a public health problem and interrupt transmission gather momentum, the potential zoonotic risk posed by livestock Schistosoma species via viable hybridisation in sub-Saharan Africa have been largely overlooked. We aimed to investigate the prevalence, distribution, and multi-host, multiparasite transmission cycle of Haematobium group schistosomiasis in Senegal, West Africa.MethodsIn this epidemiological study, we carried out systematic surveys in definitive hosts (humans, cattle, sheep, and goats) and snail intermediate hosts, in 2016–18, in two areas of Northern Senegal: Richard Toll and Lac de Guiers, where transmission is perennial; and Barkedji and Linguère, where transmission is seasonal. The occurrence and distribution of Schistosoma species and hybrids were assessed by molecular analyses of parasitological specimens obtained from the different hosts. Children in the study villages aged 5–17 years and enrolled in school were selected from school registers. Adults (aged 18–78 years) were self-selecting volunteers. Livestock from the study villages in both areas were also randomly sampled, as were post-mortem samples from local abattoirs. Additionally, five malacological surveys of snail intermediate hosts were carried out at each site in open water sources used by the communities and their animals.FindingsIn May to August, 2016, we surveyed 375 children and 20 adults from Richard Toll and Lac de Guiers, and 201 children and 107 adults from Barkedji and Linguère; in October, 2017, to January, 2018, we surveyed 386 children and 88 adults from Richard Toll and Lac de Guiers, and 323 children and 85 adults from Barkedji and Linguère. In Richard Toll and Lac de Guiers the prevalence of urogenital schistosomiasis in children was estimated to be 87% (95% CI 80–95) in 2016 and 88% (82–95) in 2017–18. An estimated 63% (in 2016) and 72% (in 2017–18) of infected children were shedding Schistosoma haematobium–Schistosoma bovis hybrids. In adults in Richard Toll and Lac de Guiers, the prevalence of urogenital schistosomiasis was estimated to be 79% (52–97) in 2016 and 41% (30–54) in 2017–18, with 88% of infected samples containing S haematobium–S bovis hybrids. In Barkedji and Linguère the prevalence of urogenital schistosomiasis in children was estimated to be 30% (23–38) in 2016 and 42% (35–49) in 2017–18, with the proportion of infected children found to be shedding S haematobium–S bovis hybrid miracidia much lower than in Richard Toll and Lac de Guiers (11% in 2016 and 9% in 2017–18). In adults in Barkedji and Linguère, the prevalence of urogenital schistosomiasis was estimated to be 26% (17–36) in 2016 and 47% (34–60) in 2017–18, with 10% of infected samples containing S haematobium–S bovis hybrids. The prevalence of S bovis in the sympatric cattle population of Richard Toll and the Lac de Guiers was 92% (80–99), with S bovis also found in sheep (estimated prevalence 14% [5–31]) and goats (15% [5–33]). In Barkedji and Linguère the main schistosome species in livestock was Schistosoma curassoni, with an estimated prevalence of 73% (48–93) in sheep, 84% (61–98) in goats and 8% (2–24) in cattle. S haematobium–S bovis hybrids were not found in livestock. In Richard Toll and Lac de Guiers 35% of infected Bulinus spp snail intermediate hosts were found to be shedding S haematobium–S bovis hybrids (68% shedding S haematobium; 17% shedding S bovis); however, no snails were found to be shedding S haematobium hybrids in Barkedji and Linguère (29% shedding S haematobium; 71% shedding S curassoni).InterpretationOur findings suggest that hybrids originate in humans via zoonotic spillover from livestock populations, where schistosomiasis is co-endemic. Introgressive hybridisation, evolving host ranges, and wider ecosystem contexts could affect the transmission dynamics of schistosomiasis and other pathogens, demonstrating the need to consider control measures within a One Health framework.FundingZoonoses and Emerging Livestock Systems programme (UK Biotechnology and Biological Sciences Research Council, UK Department for International Development, UK Economic and Social Research Council, UK Medical Research Council, UK Natural Environment Research Council, and UK Defence Science and Technology Laboratory).

Health epidemiological study: Prevalence and distribution of schistosomiasis in human

Health epidemiological study: Prevalence and distribution of schistosomiasis in human