The USAID/Government of Egypt's Schistosomiasis Research Project (SRP)

Schistosomiasis is the major public health problem in rural Egypt, with almost six million Egyptians infected as at mid-1996. In 1983, the prevalence of schistosomiasis in rural Egypt was greater than 50%, but a ten-year campaign of diagnosis and treatment has reduced the prevalence and intensity of infection. Parallel to this campaign, the government of the USA has funded a research project to examine all aspects of schistosomiasis with a view to improving the control strategy. As outlined here by Taha El Khoby, Nabil Galal and Alan Fenwick, after almost ten years, the project's achievements include: assisting WHO in its attempts to develop a vaccine against schistosomiasis, developing a suspension formulation of praziquantel suitable for young children, and establishing a unit to monitor reports of resistance to praziquantel. In addition, a large epidemiological study has established the extent of the problem in Egypt. Slow-release formulation of niclosamide, health education material for use on TV, dipstick diagnostic tests, and evaluation of ultrasound as a diagnostic tool have also been achieved. As the project closes, Egypt is left with an effective strategy for the control of schistosomiasis and several back-up tools for use in the event of development of resistance to praziquantel. The Ministry of Health and Population has the basis of a Geographical Information System (GIS) unit and the country has a trained and equipped scientific community capable of biomedical research, and almost 100 scientific papers published on their work.     

Schistosomiasis mansoni in areas of low transmission: epidemiological characterization of Venezuelan foci

Severe schistosomiasis is a rare event in Venezuela nowadays, after a successful national campaign by the Schistosomiasis Control Program. Unfortunately, this program has practically disappeared, and snail surveillance in field is not a priority, anymore. Thus, schistosomiasis has become a neglected disease in this country. However, surveys in different populations from the endemic area have shown particular epidemiological features described herein. In five communities we evaluated 2,175 persons and searched for the presence of Biomphalaria glabrata snails. Some markers were used for classifying schistosomiasis foci: mean age of the persons with Schistosoma mansoni eggs in the stools, serological tests, presence of B. glabrata snails, and intensity of infection. Places without B. glabrata snails and with few schistosomiasis cases were defined as "past transmission sites"; a site with abundant snails but few cases was defined as "potential risk"; "new transmission" foci were characterized by the presence of infected snails and young people passing eggs in the stools. A "re-emergent" focus has shared these last features, showing in addition a place where schistosomiasis had been reported before. Recent evidences of active transmission with the increasing dispersion of B. glabrata snails, point out the necessity for the re-establishment of the Schistosomiasis Control Program in Venezuela.     

Predictors of bovine Schistosoma japonicum infection in rural Sichuan,China

In China, bovines are believed to be the most common animal source of human schistosomiasis infections, though little is known about what factors promote bovine infections. The current body of literature features inconsistent, and sometimes contradictory results, and to date, few studies have looked beyond physical characteristics to identify the broader environmental conditions that predict bovine schistosomiasis. Because schistosomiasis is a sanitation-related, water-borne disease transmitted by many animals, we hypothesised that several environmental factors – such as the lack of improved sanitation systems, or participation in agricultural production that is water-intensive – could promote schistosomiasis infection in bovines. Using data collected as part of a repeat cross-sectional study conducted in rural villages in Sichuan, China from 2007 to 2016, we used a Random Forests, machine learning approach to identify the best physical and environmental predictors of bovine Schistosoma japonicum infection. Candidate predictors included: (i) physical/biological characteristics of bovines, (ii) human sources of environmental schistosomes, (iii) socio-economic indicators, (iv) animal reservoirs, and (v) agricultural practices. The density of bovines in a village and agricultural practices such as the area of rice and dry summer crops planted, and the use of night soil as an agricultural fertilizer, were among the top predictors of bovine S. japonicum infection in all collection years. Additionally, human infection prevalence, pig ownership and bovine age were found to be strong predictors of bovine infection in at least 1 year. Our findings highlight that presumptively treating bovines in villages with high bovine density or human infection prevalence may help to interrupt transmission. Furthermore, village-level predictors were stronger predictors of bovine infection than household-level predictors, suggesting future investigations may need to apply a broad ecological lens to identify potential underlying sources of persistent transmission.     

Bayesian spatial analysis of a national urinary schistosomiasis questionnaire to assist geographic targeting of schistosomiasis control in Tanzania, East Africa

Spatial modelling was applied to self-reported schistosomiasis data from over 2.5 million school students from 12,399 schools in all regions of mainland Tanzania. The aims were to derive statistically robust prevalence estimates in small geographical units (wards), to identify spatial clusters of high and low prevalence and to quantify uncertainty surrounding prevalence estimates. The objective was to permit informed decision-making for targeting of resources by the Tanzanian national schistosomiasis control programme. Bayesian logistic regression models were constructed to investigate the risk of schistosomiasis in each ward, based on the prevalence of self-reported schistosomiasis and blood in urine. Models contained covariates representing climatic and demographic effects and random effects for spatial clustering. Degree of urbanisation, median elevation of the ward and median normalised difference vegetation index (NDVI) were significantly and negatively associated with schistosomiasis prevalence. Most regions contained wards that had >95% certainty of schistosomiasis prevalence being >10%, the selected threshold for bi-annual mass chemotherapy of school-age children. Wards with >95% certainty of schistosomiasis prevalence being >30%, the selected threshold for annual mass chemotherapy of school-age children, were clustered in north-western, south-western and south-eastern regions. Large sample sizes in most wards meant raw prevalence estimates were robust. However, when uncertainties were investigated, intervention status was equivocal in 6.7-13.0% of wards depending on the criterion used. The resulting maps are being used to plan the distribution of praziquantel to participating districts; they will be applied to prioritising control in those wards where prevalence was unequivocally above thresholds for intervention and might direct decision-makers to obtain more information in wards where intervention status was uncertain.     

Elimination of schistosomiasis in China: Current status and future prospects

Elimination of schistosomiasis as a public health problem among all disease-endemic countries in 2030 is an ambitious goal. Recent achievements resulting from mass drug administration (MDA) with praziquantel is promising but may need to be complemented with also other means. Schistosomiasis was highly prevalent in China before the initiation of the national schistosomiasis control program in the mid-1950s, and, at that time, the country bore the world’s highest burden of schistosomiasis. The concerted control efforts, upheld without interruption for more than a half century, have resulted in elimination of the disease as a public health problem in China as of 2015. Here, we describe the current status of schistosomiasis in China, analyze the potential challenges affecting schistosomiasis elimination, and propose the future research needs and priorities for the country, aiming to provide more universal insights into the structures needed for a global schistosomiasis elimination encompassing also other endemic regions.     

Public health: the control of meningococcal disease in Quebec

A first outbreak of serogroup C meningococcal disease occurred in the province of Quebec in 1990-1992 and lead to a mass immunization campaign using polysaccharide vaccines. In 2001, a second outbreak was identified and a mass vaccination campaign was carried out, using the newly licensed conjugate vaccine. Clinical, epidemiological, economic and social studies were instrumental in the decision making for implementing these control programs.     

Associations between Schistosomiasis and the Use of Human Waste as an Agricultural Fertilizer in China

Background

Human waste is used as an agricultural fertilizer in China and elsewhere. Because the eggs of many helminth species can survive in environmental media, reuse of untreated or partially treated human waste, commonly called night soil, may promote transmission of human helminthiases.

Methodology/Principal Findings

We conducted an open cohort study in 36 villages to evaluate the association between night soil use and schistosomiasis in a region of China where schistosomiasis has reemerged and persisted despite control activities. We tested 2,005 residents for Schistosoma japonicum infection in 2007 and 1,365 residents in 2010 and interviewed heads of household about agricultural practices each study year. We used an intervention attributable ratio framework to estimate the association between night soil use and S. japonicum infection. Night soil use was reported by half of households (56% in 2007 and 46% in 2010). Village night soil use was strongly associated with human S. japonicum infection in 2007. We estimate cessation of night soil use would lead to a 49% reduction in infection prevalence in 2007 (95% CI: 12%, 71%). However, no association between night soil and schistosomiasis was observed in 2010. These inconsistent findings may be due to unmeasured confounding or temporal shifts in the importance of different sources of S. japonicum eggs on the margins of disease elimination.

Conclusions/Significance

The use of untreated or partially treated human waste as an agricultural fertilizer may be a barrier to permanent reductions in human helminthiases. This practice warrants further attention by the public health community.     

Costs of Illness Due to Cholera, Costs of Immunization and Cost-Effectiveness of an Oral Cholera Mass Vaccination Campaign in Zanzibar

Background

The World Health Organization (WHO) recommends oral cholera vaccines (OCVs) as a supplementary tool to conventional prevention of cholera. Dukoral, a killed whole-cell two-dose OCV, was used in a mass vaccination campaign in 2009 in Zanzibar. Public and private costs of illness (COI) due to endemic cholera and costs of the mass vaccination campaign were estimated to assess the cost-effectiveness of OCV for this particular campaign from both the health care provider and the societal perspective.

Methodology/Principal Findings

Public and private COI were obtained from interviews with local experts, with patients from three outbreaks and from reports and record review. Cost data for the vaccination campaign were collected based on actual expenditure and planned budget data. A static cohort of 50,000 individuals was examined, including herd protection. Primary outcome measures were incremental cost-effectiveness ratios (ICER) per death, per case and per disability-adjusted life-year (DALY) averted. One-way sensitivity and threshold analyses were conducted. The ICER was evaluated with regard to WHO criteria for cost-effectiveness. Base-case ICERs were USD 750,000 per death averted, USD 6,000 per case averted and USD 30,000 per DALY averted, without differences between the health care provider and the societal perspective. Threshold analyses using Shanchol and assuming high incidence and case-fatality rate indicated that the purchase price per course would have to be as low as USD 1.2 to render the mass vaccination campaign cost-effective from a health care provider perspective (societal perspective: USD 1.3).

Conclusions/Significance

Based on empirical and site-specific cost and effectiveness data from Zanzibar, the 2009 mass vaccination campaign was cost-ineffective mainly due to the relatively high OCV purchase price and a relatively low incidence. However, mass vaccination campaigns in Zanzibar to control endemic cholera may meet criteria for cost-effectiveness under certain circumstances, especially in high-incidence areas and at OCV prices below USD 1.3.     

Predicted Impact of Mass Drug Administration on the Development of Protective Immunity against Schistosoma haematobium

Previous studies suggest that protective immunity against Schistosoma haematobium is primarily stimulated by antigens from dying worms. Praziquantel treatment kills adult worms, boosting antigen exposure and protective antibody levels. Current schistosomiasis control efforts use repeated mass drug administration (MDA) of praziquantel to reduce morbidity, and may also reduce transmission. The long-term impact of MDA upon protective immunity, and subsequent effects on infection dynamics, are not known. A stochastic individual-based model describing levels of S. haematobium worm burden, egg output and protective parasite-specific antibody, which has previously been fitted to cross-sectional and short-term post-treatment egg count and antibody patterns, was used to predict dynamics of measured egg output and antibody during and after a 5-year MDA campaign. Different treatment schedules based on current World Health Organisation recommendations as well as different assumptions about reductions in transmission were investigated. We found that antibody levels were initially boosted by MDA, but declined below pre-intervention levels during or after MDA if protective immunity was short-lived. Following cessation of MDA, our models predicted that measured egg counts could sometimes overshoot pre-intervention levels, even if MDA had had no effect on transmission. With no reduction in transmission, this overshoot occurred if protective immunity was short-lived. This implies that disease burden may temporarily increase following discontinuation of treatment, even in the absence of any reduction in the overall transmission rate. If MDA was additionally assumed to reduce transmission, a larger overshoot was seen across a wide range of parameter combinations, including those with longer-lived protective immunity. MDA may reduce population levels of immunity to urogenital schistosomiasis in the long-term (3–10 years), particularly if transmission is reduced. If MDA is stopped while S. haematobium is still being transmitted, large rebounds (up to a doubling) in egg counts could occur.     

Schistosomiasis in Swaziland--a comparative study of three irrigated estates

The prevalence of Schistosomiasis and the distribution of the snail intermediate hosts on three adjoining irrigated estates in the lowveld of Swaziland was investigated. The prevalence rates of Schistosoma haematobium and S. mansoni among estate employees was lower than anticipated and there was a marked difference between the prevalence rates of S. mansoni between estates. The reasons for this and the influence of water supplies and agricultural practice on the prevalence of schistosomiasis are discussed.     

Schistosomiasis mekongi: from discovery to control

In the Mekong River basin, the first case of schistosomiasis was reported in 1957. In the 1960s, endemic areas of the infection, of which profiles were similar to those of schistosomiasis japonica, were discovered in Khong Island, Laos, to Kratie province, Cambodia. A new intermediate snail host; Neotricula aperta was identified and the Mekong strain of schistosome was elevated to a new species: Schistosoma mekongi in 1978. Baseline epidemiological surveillance was performed and schistosomiasis mekongi was described as a public health implication in the middle Mekong River basin. Because of political and economical confusion, endemic situation had become worse, and no control program had been implemented until mass treatment program with praziquantel on Khong Island in 1983. Since then, the prevalence of S. mekongi infection has rapidly decreased in each endemic area. Serological diagnosis has been useful to detect new but low endemic foci. Clinical manifestations of S. mekongi infection are similar to those of S. mansoni and S. japonicum infections. As the reduction of prevalence and intensity of S. mekongi infection, morbidity due to the disease has changed, and ultrasonographic examination is now useful to evaluate morbidity due to schistosomiasis mekongi. Transmission of the disease occurs in a couple of months during low water season. Control of N. aperta is difficult and long-lasting effective control measurements have, so far, not been available. In the next step for controling S. mekongi infection, mass treatment should be continued, and it is needed to combine other appropriate control activities.     

Have You Heard of Schistosomiasis? Knowledge,Attitudes and Practices in Nampula Province,Mozambique

BackgroundSchistosomiasis is a parasitic disease which affects almost 300 million people worldwide each year. It is highly endemic in Mozambique. Prevention and control of schistosomiasis relies mainly on mass drug administration (MDA), as well as adoption of basic sanitation practices. Individual and community perceptions of schistosomiasis are likely to have a significant effect on prevention and control efforts. In order to establish a baseline to evaluate a community engagement intervention with a focus on schistosomiasis, a survey to determine knowledge, attitudes and practices relating to the disease was conducted.Conclusion/SignificancePoor knowledge of the causes of schistosomiasis and how to prevent it, coupled with persisting misconceptions, continue to pose barriers to effective disease prevention and control. To achieve high levels of uptake of MDA and adoption of protective behaviours, it will be essential to engage individuals and communities, improving their understanding of the causes and symptoms of schistosomiasis, recommended prevention mechanisms and the rationale behind MDA.     

A review of female genital schistosomiasis

In a review of the studies on genital schistosomiasis, the cervix, the Fallopian tubes, and the vagina are the most common gynaecological sites to harbour Schistosoma haematobium. Lesions are caused by host responses to dead or viable schistosomiasis eggs and may render women with genital schistosomiasis susceptible to HIV. The typical genital changes, such as sandy patches and pathological blood vessels may make women susceptible to super-infection, cause contact bleeding, decreased fertility, abortions, discharge and bleeding. Further research is needed to find simple, low-tech diagnostic methods, treatment for chronic lesions, and to explore the preventive effects of mass drug administration on symptoms, sandy patches, HPV and the HIV epidemic.     

Estimating the global distribution of field size using crowdsourcing

There is an increasing evidence that smallholder farms contribute substantially to food production globally, yet spatially explicit data on agricultural field sizes are currently lacking. Automated field size delineation using remote sensing or the estimation of average farm size at subnational level using census data are two approaches that have been used. However, both have limitations, for example, automatic field size delineation using remote sensing has not yet been implemented at a global scale while the spatial resolution is very coarse when using census data. This paper demonstrates a unique approach to quantifying and mapping agricultural field size globally using crowdsourcing. A campaign was run in June 2017, where participants were asked to visually interpret very high resolution satellite imagery from Google Maps and Bing using the Geo‐Wiki application. During the campaign, participants collected field size data for 130 K unique locations around the globe. Using this sample, we have produced the most accurate global field size map to date and estimated the percentage of different field sizes, ranging from very small to very large, in agricultural areas at global, continental, and national levels. The results show that smallholder farms occupy up to 40% of agricultural areas globally, which means that, potentially, there are many more smallholder farms in comparison with the two different current global estimates of 12% and 24%. The global field size map and the crowdsourced data set are openly available and can be used for integrated assessment modeling, comparative studies of agricultural dynamics across different contexts, for training and validation of remote sensing field size delineation, and potential contributions to the Sustainable Development Goal of Ending hunger, achieve food security and improved nutrition and promote sustainable agriculture.     

Three Gorges Dam and Its Impact on the Potential Transmission of Schistosomiasis in Regions along the Yangtze River

Large-scale hydroprojects have a propensity for incurring schistosomiasis epidemics by altering the environments of their vicinities. As the construction of the Three Gorges Dam, one of the world’s largest hydroprojects to date, draws near its conclusion, an assessment of the dam’s capacity in causing schistosomiasis becomes more urgent and pressing. This article reviews recent investigations into the possible effects of the dam on schistosomiasis in the Three Gorges region and areas along the Yangtze downstream from the dam. Data used in this article were extracted from peer-reviewed papers found in PubMed, Chinese Journal of Parasitology and Parasitic Diseases, and Chinese Journal of Schistosomiasis Control. Results indicate that the Three Gorges Dam is capable of inducing a wide variety of environmental and ecological changes both within the Three Gorges region and in downstream areas. These changes, however, carry ambivalent implications for the reproduction of Oncomelania snails and the spreading of schistosome infections. Furthermore, major changes in the demographics and agricultural practices of the Three Gorges and downstream Yangtze areas caused by the dam could also exert significant influence on the transmission of schistosomiasis in these regions. Major conclusions of this review include the need for further ecological simulations of the Three Gorges Dam and the need for deploying monitoring and intervention systems to provide successful prophylaxis of the Three Gorges Dam-associated schistosomiasis emergence.     

Schistosomiasis messaging in endemic communities: Lessons and implications for interventions from rural Uganda,a rapid ethnographic assessment study

BackgroundOver 240 million people are infected with schistosomiasis, the majority in sub-Saharan Africa. In Uganda, high infection rates exist in communities on the shores of Lake Victoria. Praziquantel mass drug administration (MDA) delivered by village health teams is the mainstay of schistosomiasis control. However, treatment uptake remains suboptimal, with many people unaware of treatment or thinking it is only for children. Furthermore, people are often rapidly reinfected post-treatment due to continued exposure. In three Schistosoma mansoni high endemicity lake-shore communities in Mayuge district, Eastern Uganda, we investigated the sources of schistosomiasis information, remembered content of information, and the perception of information and related practices towards the control of schistosomiasis.Methods and principal findingsData were collected from September 2017 to March 2018 using a rapid ethnographic assessment that included transect walks, observations, individual in-depth interviews and focus group discussions. Data were analysed thematically using iterative categorisation. We found that the main sources of schistosomiasis information included health workers at government facilities, village health teams, teachers, and radio programmes produced by the Ministry of Health. These messages described the symptoms of schistosomiasis, but did not mention the side effects of praziquantel treatment. Despite this messaging, the main cause of the disease and transmission was unclear to most participants. The translation of schistosomiasis on the radio into the local language ‘ekidada’—meaning swollen stomach—increased, rather than reduced, confusion about the cause(s) of schistosomiasis, due to believed links between ekidada and witchcraft, and prompted a reluctance to engage with treatment or preventative efforts.Conclusion and significanceThis study highlights gaps in schistosomiasis messaging. We recommend MDA is complemented by effective, evidence-based messaging on schistosomiasis transmission, prevention, and treatment, that is sensitive to local language and context issues, resulting in clear, concise, and consistent messages, to increase effectiveness.     

Public health response to an anthrax attack: an evaluation of vaccination policy options

A discrete-time, deterministic, compartmental model was developed and analyzed to provide insight into how the use of anthrax vaccine before or after a large-scale attack can reduce casualties. The model accounts for important response and protection factors such as antibiotic and vaccine efficacy, the protective effects of buildings, the timing of emergency response, and antibiotic adherence and vaccine coverage in the population prior to the attack. The relative benefit of pre- versus post-exposure vaccination is influenced by the timing of the post-exposure antibiotic distribution campaign as well as assumptions of antibiotic adherence. The results indicate that, regardless of which vaccination policy is adopted, a rapid and effective post-attack medical response has a large impact on the number of lives that can be saved by a post-exposure prophylaxis (PEP) campaign. A sensitivity analysis of the model indicates that uncertainty in medical efficacy and the time to initiate a PEP campaign are the model parameters that have the greatest impact on the number of predicted deaths. It is shown that for each day that a mass prophylaxis campaign is delayed, more casualties and deaths result than for each day that the completion of the campaign is delayed.     

The evaluation of a mass media campaign aimed at weight gain prevention among young Dutch adults

Objective: The objective was to evaluate a 3‐year nationwide mass media campaign aimed at preventing weight gain. The campaign was aimed primarily at raising awareness of the importance of weight‐gain prevention and bringing these issues to the attention of the Dutch public. Research Methods and Procedures: Eleven serial, independent, cross‐sectional, population‐based telephone surveys were used to assess campaign awareness and impact (N ranged between 483 and 493 for each of the 11 surveys). The surveys were conducted before and after six campaign waves. Multiple linear and logistic regression analyses were used to test for trends over time and for differences among the surveys for campaign awareness, message recall, perceived body weight status, overweight‐related risk perceptions, attitudes, perceived social support, self‐efficacy expectations, and motivations for preventing weight gain. Results: Campaign awareness ranged from 61% after the 1st campaign wave to 88.4% after the final wave. The campaign's television broadcasting activities were an important source of campaign awareness, from both the campaign's television commercials and television‐based free publicity. Message recall ranged from 41.9% to 68.1%. Small positive differences were found in attitudes, perceived social support, and intentions for preventing weight gain. Additionally, the results suggest mixed effects on self‐efficacy expectations and a negative effect on risk perception. Discussion: The campaign resulted in high campaign awareness, especially as a result of television commercials and free publicity on television. The results suggest that the campaign was able to create more positive attitudes and motivation but lower risk perceptions and efficacy for preventing weight gain.     

Prevalence of Schistosomes and Soil-Transmitted Helminths among Schoolchildren in Lake Victoria Basin,Tanzania

The objectives of this study was to conduct a survey on schistosomiasis and soil-transmitted helminth (STH) infections in order to come up with feasible control strategies in Lake Victoria basin, Tanzania. Depending on the size of the school, 150-200 schoolchildren were recruited for the study. Duplicate Kato-Katz stool smears were prepared from each child and microscopically examined for Schistosoma mansoni and STHs. Urine specimens were examined for Schistosoma haematobium eggs using the filtration technique. After the survey, mass drug administration was done using praziquantel and albendazole for schistosomiasis and STHs infections, respectively. A total of 5,952 schoolchildren from 36 schools were recruited for the study and had their stool and urine specimens examined. Out of 5,952 schoolchildren, 898 (15.1%) were positive for S. mansoni, 754 (12.6%) for hookworms, 188 (3.2%) for Ascaris lumblicoides, and 5 (0.008%) for Trichuris trichiura. Out of 5,826 schoolchildren who provided urine samples, 519 (8.9%) were positive for S. haematobium eggs. The results revealed that intestinal schistosomiasis, urogenital schistosomiasis, and STH infections are highly prevalent throughought the lake basin. The high prevalence of intestinal and urogenital schistosomisiasis in the study area was a function of the distance from Lake Victoria, the former being more prevalent at localities close to the lake, whilst the latter is more so away from it. Control of schistosomiasis and STHs in the study area requires an integrated strategy that involves provision of health education to communities, regular treatments, and provision of adequate safe water supply and sanitation facilities.