Control of schistosomiasis mansoni in a small north east Brazilian community

FioSchisto's expert perspective on implementing WHO guidelines for schistosomiasis control and transmission elimination in Brazil

The World Health Organization (WHO) recognizes schistosomiasis as one of the Neglected Tropical Diseases targeted for global elimination in the 2030 Agenda of the Sustainable Development Goals. In Brazil, schistosomiasis mansoni is considered a public health problem, particularly prevalent among vulnerable populations living in areas with poor environmental and sanitary conditions. In 2022, the WHO published a Guideline encompassing recommendations to assist national programs in endemic countries in achieving morbidity control, eliminating schistosomiasis as a public health problem, and advancing towards interrupting transmission. The perspectives presented here, collectively prepared by members of the Oswaldo Cruz Foundation's (Fiocruz) Schistosomiasis Translational Program (FioSchisto), along with invited experts, examine the feasibility of the WHO recommendations for the Brazilian settings, providing appropriate recommendations for public health policies applicable to the epidemiological reality of Brazil, and suggests future research to address relevant issues. In Brazil, the provision of safe water and sanitation should be the key action to achieve schistosomiasis elimination goals. The agencies involved in measures implementation should act together with the Primary Care teams for planning, executing, monitoring, and evaluating actions in priority municipalities based on their epidemiological indicators. Host snails control should prioritize judicious ecological interventions at breeding sites. The Information, Education, and Communication (IEC) strategy should be associated with water and sanitation and other control actions, actively involving school community. To identify infected carriers, FioSchisto recommends a two-stage approach of immunological and molecular tests to verify transmission interruption during the intervention and beyond. Praziquantel administration should be done under medical supervision at the Primary Care level. MDA should be considered in exceptional settings, as a measure of initial attack strategy in locations presenting high endemicity, always integrated with water and sanitation, IEC, and snail control. To assist decision-making, as well as the monitoring and evaluation of strategic actions, there is a need for an Information System. FioSchisto considers this systematization essential to make investments in strategic research to support the improvement of schistosomiasis control actions. Efforts toward schistosomiasis elimination in Brazil will succeed with a paradigm shift from the vertical prescriptive framework to a community-centered approach involving intersectoral and interdisciplinary collaboration.

Schistosoma haematobium infection status and its associated risk factors among pregnant women in Munyenge, South West Region, Cameroon following scale-up of communal piped water sources from 2014 to 2017: a cross-sectional study

Background

In 2014, a study in Munyenge revealed a high prevalence of urogenital schistosomiasis (UGS) among pregnant women. This study investigated he prevalence and risk factors of UGS in pregnancy following scale-up of piped water sources from 2014 to 2017. Secondly, we compared stream usage, stream contact behaviour, infection rate and intensity with the findings of 2014.

Methods

Consenting pregnant women reporting for antenatal care (ANC) in the different health facilities were enrolled consecutively between November 2016 and January 2018. Information on age, gravidity status, residence, marital status, educational level, occupation, household water source, frequency of contact with water and stream activities were obtained using a semi-structured questionnaire. Urine samples were examined for the presence of microhaematuria and S. haematobium ova using test strip and filtration/microscopy methods respectively. Data were analysed using univariate and multivariate regression analyses and relative risk reductions calculated.

Results

Of the 368 women enrolled, 22.3% (82) were diagnosed with UGS. Marital status (single) (aOR = 2.24, 95% CI: 1.04–4.79), primary - level of education (aOR = 2.0; 95% CI: 1.04–3.85) and domestic activity and bathing in the stream (aOR = 3.3; 95% CI: 1.83–6.01) increased risk of S. haematobium infection. Meanwhile, fewer visits (< 3 visits/week) to stream (aOR = 0.35, 95% CI = 0.17–0.74) reduced exposure to infection. Piped water usage was associated with reduced stream usage and eliminated the risk of infection among women who used safe water only. Compared with the findings of 2014, stream usage (RRR = 23 95% CI: 19–28), frequency (≥ 3 visits) (RRR = 69 95% CI: 59–77) and intensity of contact with water (RRR = 37 95% CI = 22–49) has reduced. Similarly, we observed a decrease in infection rate (RRR = 52, 95% CI = 40–62) and prevalence of heavy egg intensity (RRR = 71, 95% CI = 53–81).

Conclusion

Following increased piped water sources in Munyenge, S. haematobium infection has declined due to reduced stream contact. This has important implication in the control of UGS in pregnancy.

Electronic supplementary material

The online version of this article (10.1186/s12889-019-6659-7) contains supplementary material, which is available to authorized users.

To Reduce the Global Burden of Human Schistosomiasis, Use 'Old Fashioned' Snail Control

Control strategies to reduce human schistosomiasis have evolved from 'snail picking' campaigns, a century ago, to modern wide-scale human treatment campaigns, or preventive chemotherapy. Unfortunately, despite the rise in preventive chemotherapy campaigns, just as many people suffer from schistosomiasis today as they did 50 years ago. Snail control can complement preventive chemotherapy by reducing the risk of transmission from snails to humans. Here, we present ideas for modernizing and scaling up snail control, including spatiotemporal targeting, environmental diagnostics, better molluscicides, new technologies (e.g., gene drive), and 'outside the box' strategies such as natural enemies, traps, and repellants. We conclude that, to achieve the World Health Assembly's stated goal to eliminate schistosomiasis, it is time to give snail control another look.

Schistosomiasis Prevalence and Intensity of Infection in Latin America and the Caribbean Countries, 1942-2014: A Systematic Review in the Context of a Regional Elimination Goal

Background

In 2012 the World Health Assembly adopted resolution WHA65.21 on elimination of schistosomiasis, calling for increased investment in schistosomiasis control and support for countries to initiate elimination programs. This study aims to analyze prevalence and intensity of Schistosoma mansoni infection in children in Latin America and the Caribbean countries and territories (LAC), at the second administrative level or lower.

Methodology

A systematic review of schistosomiasis prevalence and intensity of infection was conducted by searching at PubMed, LILACS and EMBASE. Experts on the topic were informally consulted and institutional web pages were reviewed (PAHO/WHO, Ministries of Health). Only SCH infection among children was registered because it can be a ‘proxi-indicator’ of recent transmission by the time the study is conducted.

Principal Findings

One hundred thirty two full-text articles met the inclusion criteria and provided 1,242 prevalence and 199 intensity of infection data points. Most of them were from Brazil (69.7%). Only Brazil published studies after 2001, showing several 'hot spots' with high prevalence. Brazil, Venezuela, Suriname and Saint Lucia need to update the epidemiological status of schistosomiasis to re-design their national programs and target the elimination of Schistosoma mansoni transmission by 2020. In Antigua and Barbuda, Dominican Republic, Guadeloupe, Martinique, Montserrat and Puerto Rico schistosomiasis transmission may be interrupted. However the compilation of an elimination dossier and follow-up surveys, per WHO recommendations, are needed to verify that status. Hence, the burden of subtle SCH chronic infection may be still present and even high in countries that may have eliminated transmission. Heterogeneity in the methodologies used for monitoring and evaluating the progress of the schistosomiasis programs was found, making cross-national and chronological comparisons difficult.

Conclusions

There is a need for updating the schistosomiasis status in the historically endemic countries and territories in LAC to address the required public health interventions for control and elimination programs or to verify the elimination of transmission of Schistosoma mansoni. Improved reporting and standardization of the monitoring and evaluation methodologies used are recommended, while using available WHO guidelines. Meeting a regional elimination goal will require additional and improved epidemiological data by age group and sex.

Schistosomiasis (Schistosoma spp) is an intestinal parasitic infection that causes anaemia, stunted growth, impaired cognition, and decreased physical fitness among other pathological effects. Currently, the control of schistosomiasis relies principally on mass drug administration of praziquantel. In addition, the implementation of further interventions such as snail (intermediate host) control, improving access to safe water and sanitation are required to achieve elimination of transmission in humans. An updated epidemiological situation will help countries to design tailor-made interventions enabling a step-up in prevention and control measures with the goal of elimination of transmission of this disease by 2020. In the region of the Americas, Schistosoma mansoni is the only species present that infect humans. This systematic review shows that in this region there is a need for re-mapping the schistosomiasis epidemiological situation in certain areas and countries in order to implement and optimize the best public health interventions needed to interrupt transmission or verify elimination of transmission. The methodology for monitoring and evaluating schistosomiasis control programs are well defined by current WHO guidelines. However, further investigations and guidelines on suitable tools for monitoring and evaluating schistosomiasis elimination programs and criteria and procedures for validating the elimination are required, and are currently being undertaken by WHO.

Systematic Review and Meta-analysis of the Impact of Chemical-Based Mollusciciding for Control of Schistosoma mansoni and S. haematobium Transmission

Background

Programs for schistosomiasis control are advancing worldwide, with many benefits noted in terms of disease reduction. Yet risk of reinfection and recurrent disease remain, even in areas with high treatment coverage. In the search for means to better prevent new Schistosoma infections, attention has returned to an older strategy for transmission control, i.e., chemical mollusciciding, to suppress intermediate host snail species responsible for S. mansoni and S. haematobium transmission. The objective of this systematic review and meta-analysis was to summarize prior experience in molluscicide-based control of Bulinus and Biomphalaria spp. snails, and estimate its impact on local human Schistosoma infection.

Methodology/Principal Findings

The review was registered at inception with PROSPERO (CRD42013006869). Studies were identified by online database searches and hand searches of private archives. Eligible studies included published or unpublished mollusciciding field trials performed before January 2014 involving host snails for S. mansoni or S. haematobium, with a primary focus on the use of niclosamide. Among 63 included papers, there was large variability in terms of molluscicide dosing, and treatment intervals varied from 3–52 weeks depending on location, water source, and type of application. Among 35 studies reporting on prevalence, random effects meta-analysis indicated that, on average, odds of infection were reduced 77% (OR 0.23, CI_95% 0.17, 0.31) during the course of mollusciciding, with increased impact if combined with drug therapy, and progressively greater impact over time. In 17 studies reporting local incidence, risk of new infection was reduced 64% (RR 0.36 CI_95% 0.25, 0.5), but additional drug treatment did not appear to influence incidence effects.

Conclusion/Significance

While there are hurdles to implementing molluscicide control, its impact on local transmission is typically strong, albeit incomplete. Based on past experience, regular focal mollusciciding is likely to contribute significantly to the move toward elimination of schistosomiasis in high risk areas.

Infection with Schistosoma blood flukes is a leading cause of chronic parasitic disease in at-risk areas of Africa, South America, Asia, and the Philippines. Over past decades, many national programs have implemented regular drug treatment to control or prevent the advanced complications of Schistosoma infection. However, these periodic treatments do not stop transmission of the parasite, which occurs when human sewage contaminates local water bodies and parasite eggs infect intermediate host snails. In this systematic review, we collated past experience of using chemically-mediated snail control for prevention of schistosomiasis. This approach, used in many Schistosoma-affected countries before the advent of the current oral drug regimens, has the potential to significantly reduce transmission if properly applied. Our meta-analysis of 63 studies (performed 1953–1981) catalogued a wide variety of water treatments and schedules employed. Among studies reporting on human infection, we found that snail control reduced local human prevalence and incidence of infection in most, but not all locations. Estimates from the aggregated studies indicate that snail control (alone) typically reduced new infections by 64% and local prevalence declined over a period of years. This decline was accelerated and more profound (84% reduction) if drug treatment was also made available.

Geographical analysis of the role of water supply and sanitation in the risk of helminth infections of children in West Africa

Globally, inadequate water supply, sanitation, and hygiene (WASH) are major contributors to mortality and burden of disease. We aimed to quantify the role of WASH in the risk of Schistosoma hematobium, Schistosoma mansoni, and hookworm infection in school-aged children; to estimate the population attributable fraction (PAF) of helminth infection due to WASH; and to spatially predict the risk of infection. We generated predictive maps of areas in West Africa without piped water, toilet facilities, and improved household floor types, using spatial risk models. Our maps identified areas in West Africa where the millennium development goal for water and sanitation is lagging behind. There was a generally better geographical coverage for toilets and improved household floor types compared with water supply. These predictions, and their uncertainty, were then used as covariates in Bayesian geostatistical models for the three helminth species. We estimated a smaller attributable fraction for water supply in S. mansoni (PAF 47%) compared with S. hematobium (PAF 71%). The attributable fraction of S. hematobium infection due to natural floor type (PAF 21%) was comparable to that of S. mansoni (PAF 16%), but was significantly higher for hookworm infection (PAF 86%). Five percent of hookworm cases could have been prevented if improved toilet facilities had been available. Mapping the distribution of infection risk adjusted for WASH allowed the identification of communities in West Africa where preventive chemotherapy integrated with interventions to improve WASH will yield the greatest health benefits.

Socioeconomic studies of schistosomiasis in Brazil: a review

This review finds considerable evidence that socioeconomic status has significantly influenced the transmission, spread and treatment of schistosomiasis in Brazil. High infection rates persist among both the rural and urban poor. Rural living, poor housing and water supplies and low educational level were major factors in schistosomiasis occurrence among agricultural populations. In urban areas, prevailing living conditions in shantytowns and labor migrations from and periodic return movements to rural areas were predictive of schistosomiasis. The risk of the establishment of new transmission foci exists in both rural and urban areas, conferred by and affecting poorer people. Associations between schistosomiasis and socioeconomic parameters, persisting inequities in health services accessibility, prevailing health impacts of schistosomiasis, and the ongoing decentralization of health services point to opportunities and strategies for focused interventions aimed at promoting health-enhancing behavior and living conditions and improving access to health care. The authors call for multidisciplinary studies to better examine the complexities of the socioeconomic environment in relation to schistosomiasis and for economic programs to reduce prevailing socioeconomic inequalities.

Low transmission areas of schistosomiasis in Venezuela: consequences on the diagnosis, treatment, and control

Schistosomiasis low transmission areas as Venezuela, can be defined as those where the vector exists, the prevalence of active cases is under 25%, individuals with mild intensity of infection predominate and are mostly asymptomatic. These areas are the consequence of effective control programs, however, "silent" epidemiological places are difficult to trace, avoiding the opportune diagnosis and treatment of infected persons. Clinic and abdominal ultrasound have not shown to discriminate infected from uninfected persons in areas where besides Schistosoma mansoni, intestinal parasites are the rule. Under these conditions, serology remains as a very valuable diagnostic tool, since it gives a closer approximation to the true prevalence. In this sense, circumoval precipitin test, ELISA-SEA with sodium metaperiodate, and alkaline phosphatase immunoassay joined to coprology allow the identification of the "schistosomiasis cases". In relation to public health, schistosomiasis has been underestimated by the sanitary authorities and the investment on its control is being transferred to other diseases of major social and political relevance neglecting sanitary efforts and allowing growth of snail population. Some strategies of diagnosis and control should be done before schistosomiasis reemergence occurs in low transmission areas.

Socioeconomic determinants of schistosomiasis in a poor rural area in Brazil

The objective of this paper is to identify and quantify socioeconomic determinants of Schistosoma mansoni infection in the rural area of Virgem das Graças in Minas Gerais State of Brazil. A cross-sectional study was carried out to examine the prevalence and intensity of schistosomiasis in relation to socioeconomic characteristics of the households. Log-binomial regression analysis was used to examine the data on both the household and individual levels, analyzing the prevalence ratios for the association of schistosomiasis and socioeconomic variables related to the head of the household. Multiple comparisons through mixed effect modeling were used to examine the relationship between intensity of infection (geometric mean egg counts) and different levels of socioeconomic variables, respectively. In the univariate analysis, place of residence, number of persons per room, and lack of motorized transport were associated with schistosomiasis at the household level and age and unsafe water contact at the individual level. Age, unsafe water contact, number of persons per room, household possessions and lack of education of head of household remained significant predictors of schistosomiasis in the multivariable analysis. Only age was significantly associated with intensity of infection of individuals. It is concluded that widespread poverty, the rural environment, and weak socioeconomic differentiation that result in intense contact with infective water appear to minimize the protective effect of piped water supply and other socioeconomic parameters on schistosomiasis found in other studies. The potential role of socioeconomic development in conjunction with schistosomiasis control is described and areas for further studies are identified.

The role of the scientific research in the control of schistosomiasis in endemic areas

The way the researches established the lines of direction for considering fight against schistosomiasis on the double aspect of transmission and morbidity control is outstanding. Chemotherapy in the morbidity control is emphasized. The research priorities for schistosomiasis control are mentioned.

Exposure to Schistosoma mansoni infection in a rural area in Brazil. Part III: household aggregation of water-contact behaviour

Much research points to the importance of the household in the study of water-borne diseases such as schistosomiasis. An important aspect of the household is the clustering of domestic activities associated with water collection, storage and usage. Such activities can result in the sharing of water-contact sites and water-contact behaviour, which expose household members to similar risks of infection. In previous studies, we determined that shared residence accounted for 28% of the variance in Schistosoma faecal egg excretion rates. We now quantify the effect of shared residence on the variation in water-related health behaviours. We found that shared residence accounted for 30% of the variation in total water contacts per week. It also accounted for a large proportion of the variation in individual water-contact behaviour: e.g. agricultural contacts (63%), washing limbs (56%) or bathing (41%). These results implicate the household as an important composite measure of the complex relationships between socioeconomic, environmental and behavioural factors that influence water-contact behaviour and, therefore, the transmission of schistosomiasis. Our results also support a focus on the household in the implementation of schistosomiasis prevention and control efforts.

The role of health education and sanitation in the control of helminth infections

Health education and sanitation are two important components of primary health care system introduced by the World Health Organization (WHO) as a basis for the prevention and control of communicable diseases. However, the roles of health education and sanitation in disease control have been controversial, especially in the wake of recent advances in safe and effective oral drugs. This article has reviewed the various health education and sanitation interventions around the world to determine what roles they have played in the past relative to other intervention strategies and the role they have to play in future control efforts. It appears clear-cut from the review, that while chemotherapy has been and will remain the best option for morbidity control, sanitation has an important role to play not only to sustain the benefits of chemotherapy but also to protect the uninfected. Health education that is effective, simple and low-cost remains the only tool for creating the enabling environment for both chemotherapy and sanitation to thrive.

Schistosomiasis mansoni in Bananal (State of São Paulo, Brazil): IV. Study on the public awareness of its risks in the Palha District

A rather high prevalence of mansoni schistosomiasis has been observed in some localities of Bananal, State of São Paulo, during the past decade. The highest prevalence of schistosomiasis was found in the Palha District; it was thus considered adequate for an evaluation of public awareness of the risks involved in acquiring schistosomiasis, a likely outcome of certain behavior patterns. We interviewed 542 district-dwellers. The 5-to-39 age-group constituted 65.5% of the whole sample. Concerning the infection, 69.2% had hearsay information; 46.1% know the infection; 69.6% know how it is acquired; 31.5% know about the symptoms and 57.1% know what can be done to avoid infection; 17.7% declared to have acquired the infection at least once in their lifetime; 62.3% reported total or partial immersion in collections of water of Bananal, once or twice a week, 53.9% of these for bathing or fishing. Although most (91.7%) households have treated running water, are connected to the sewage network or have septic tanks, 9% of the people interviewed use to defecate on the field. It became clear that the educational messages aimed at this population had not been adequate, having failed to fulfil any expectations. The local people received only piecemeal and subjective information about their problem. The control of schistosomiasis requires an integrated practice, which includes the analysis of macro-determinant factors, such as basic sanitation, habitation, education and health care. In short, we require a multidisciplinary vision of the mechanisms of transmission of the infection, which depends upon adequate planning and well trained personnel, intent on their educational work, to attain satisfactory results.

Factors associated with Schistosoma mansoni infection 5 years after selective treatment in a low endemic area in Brazil

Five years after a single dose treatment, prevalence, intensity and morbidity of schistosomiasis mansoni were evaluated in Agua Branca, a low endemic community in the South East Brazil (cure rate 94%). At community level, prevalence showed a decrease from 38.9 to 24.5% and the intensity of infection dropped from 119.5 to 38.9 eggs per g of faeces (epg). However, after the exclusion of immigrants, newborn children and individuals that had left the area after the first evaluation, the prevalence among the treated and followed population was not significantly affected. Multivariate analysis showed that the 10-29 age group and water contact for agricultural purposes were independently associated with the presence of infection on post treatment evaluation [OR 3.9 and 5.09, respectively]. A previous treatment among subjects older than 15 years was inversely associated [OR 0.58]. The authors wish to draw attention to the fact that mobility may lead to a serious bias in evaluating the impact of the control programme.

[Evaluation of control measures implemented from 1977 to 1996 in the endemic area of schistosomiasis in Pernambuco, Brazil]

This study assesses the evolution of schistosomiasis in the endemic area of Pernambuco, using data from five campaigns of chemotherapy control carried out by national health programmes from 1977 to 1996. Analysis of the data showed that: a) the proportion of municipalities with prevalence above 25% was significantly higher in the coastal-forest zone than in the zone of transitional vegetation Agreste in the four evaluations made in the endemic area; b) the prevalence of infection decreased in both zones even when the interval between campaigns were more than five years. The last survey (1996) indicated a predominance of municipalities with prevalences below 25%. However, the majority of these municipalities had localities with prevalence above 50%. A proposal is presented for the identification of the problematic localities, where complementary measures to chemotherapy, such as systematic snail control, improved sanitation, health education and community mobilization, are still necessary.

The control of schistosomiasis in Brazil: an ethnoepidemiological study of the effectiveness of a community mobilization program for health education

This study combined anthropological and epidemiological approaches to assess the effectiveness of community mobilization for health education, developed as part of the Brazilian program for the control of schistosomiasis. The study was carried out in two villages in the state of Minas Gerais, SE Brazil, exposed to the same established schistosomiaisis control strategies. Residents of one village were also exposed to the community mobilization for health education (study area) while those from the other community were not exposed to this program (control area). Schistosoma mansoni prevalence rates for the study and control villages were compared over time. A population-based survey was carried out in the two villages to obtain information on socio-demographic factors, water contact patterns and knowledge of S. mansoni transmission. Intensive ethnographic interviews with key informants in each locality were employed to determine the knowledge, attitudes and practices of the communities regarding schistosomiasis. Ethnographic data were analysed using the model of systems of signs, meanings and actions. Differences were observed in prevalence trends between the study and control areas but they could not be explained by the existence of the community mobilization program in the former. It was also found that educational actions carried out by the Brazilian Ministry of Health transmitted information on schistosomiasis but were ineffective in transforming the information received into preventive behaviour related to water contact. With regard to disease, the population studied tended to distinguish minor symptoms, which they associated with water contact, from major symptoms, which they attributed to lack of medical treatment. This distinction mediated perceptions of the severity of "xistose" and reduced the importance of avoiding contact with potentially infested waters. The perception of protection conferred by treatment observed in the present study might also apply to other communities where access to treatment is readily available and free. The extent to which this perception exists in endemic areas needs to be determined so that apparent contradictions of this type can be addressed in future educational programs.

Participação popular no controle da esquistossomose através do Sistema Único de Saúde (SUS), em Taquaraçu de Minas, (Minas Gerais, Brasil), entre 1985-1995: construção de um modelo alternativo

Foi avaliado o programa de controle da esquistossomose realizado em Taquaraçu de Minas, MG, entre 1985 e 1995. A medida de controle adotada foi a participação popular nas ações de controle: tratamento seletivo, saneamento e educação popular. A equipe de saúde local foi capacitada para gerenciar o programa, conforme proposta do SUS. O fornecimento de água potável foi oferecido a 97% das residências no núcleo do Município. Em 1995, foi realizada análise para identificação dos fatores de risco responsáveis pela manutenção da transmissão da esquistossomose. A prevalência da infecção entre 1985-1995 apresentou-se sete vezes menor, passando de 30,9% para 4,3%, respectivamente. A intensidade de infecção também sofreu significativa redução, passando de 91,2 ± 6,1 para 30,7 ± 2,5 (p = 0,00) no mesmo período. A municipalização desse programa de controle da esquistossomose através do SUS, usando-se um tratamento seletivo, fornecimento de água potável intradomiciliar com participação popular nas medidas de controle, seguido de atendimento da demanda espontânea, apresentou resultados duradouros, apontando a possibilidade de uso deste modelo para outras áreas endêmicas com características semelhantes.

[The effectiveness of the Program of Communication and Education in Health on the control of S. mansoni infection in some areas of the state of Bahia]

The Program for S. mansoni Control (PCE) has been developed in some areas of the State of Bahia by the Fundação Nacional de Saúde (FNS). In 1989, activities on Information, Education, Communication and Community Mobilization (IEC/MC) were initiated. This study evaluates the epidemiological impact of the IEC/MC, using a quasi-experimental study design strategy, comparing the prevalences of infection for S. mansoni in areas of IEC/MC and estimates of other areas. The data used were routinely collected by the local staff of the FNS. A decrease on the prevalence of S. mansoni infection was found in all study areas, specially in those of IEC/MC activities. Findings indicate that PCE activities are more effective among school-age individuals and male adults, although IEC/MC allows for higher epidemiological impact among women, reflecting the differences among the strategies. These findings point out the need for qualitative evaluation research, as well as cost benefit and cost effectiveness analyses, that are more appropriate for decision making processes.

[Schistosomiasis mansoni in urban territory. 2. A theoretical approach to the accumulation, concentration, and centralization of capital and the production of disease]

This study discusses the urbanization of schistosomiasis in the Greater Metropolitan Area of Belo Horizonte, Minas Gerais, Brazil. The observation that schistosomiasis has become endemic in an urban area is discussed using the concept of social organization of space as an exercise in providing an operational basis for the social and environmental paradigms of collective health. Elements from the new world economic order are discussed: the concept of socially constructed space, the internationalization of capital, the periphery, and the resulting collective disease generation process. Due to the deterioration of state health services and the logic of the new world economic order, the need for local schistosomiasis control solutions is stressed.

[Schistosomiasis mansoni occurrence in urban territory. 1. A case study of a peripheral urban area in Belo Horizonte, Minas Gerais, Brazil]

This article characterizes the etiological conditions for schistosomiasis mansoni in the urban portion of the Greater Metropolitan Area of Belo Horizonte, Minas Gerais. Knowledge about this endemic disease is discussed with a clinical focus on subjects who lived in endemic areas from 1946 to 1994, taking into account the specific indicators for the endemic disease according to the measures adopted in its control.

Control of schistosomiasis mansoni in Ravena (Sabará, state of Minas Gerais, Brazil) through water supply and quadrennial treatments

In this study, the results obtained in a control programme of schistosomiasis in Ravena (Sabará, Minas Gerais) between 1980 and 1992 are evaluated. Control measures used in this programme were: specific treatment of the people infected with Schistosoma mansoni at four year-intervals (1980/84/88) and the supply of tap water to 90% of the residences in 1980. A significant reduction of the prevalence (36.7% to 11.5%, p < or = 0.05) and of the intensity of the infection (228.9 eggs per gram of feces (epg), s = 3.7 to 60.3 epg, s = 3.5, p < or = 0.05) was observed. No cases of the severe form of the disease were diagnosed in the area. Factors independently associated with the infection were in 1980 daily sand extraction and the lack of tap water in residences and in 1992 daily sand extraction and fishing and weekly swimming. Concluding, the supply of tap water together with quadrennial treatments significantly diminished both the prevalence and intensity of the S. mansoni infection, with the additional gain of persistent low indices even after four-year intervals between the treatments.

[Alternative approaches to the control of schistosomiasis: trying to include subjective elements in epidemiology]

This study discusses the possibility of integrating the "subjective" in epidemiological research. Alternative approaches are presented for programs to provide health and educational services, as well as others which are the right of citizens to receive and the responsibility of the government to provide. The characteristics of participatory research, community-based epidemiology, and popular education programs are described, with the purpose of constructing a model for the control of schistosomiasis using alternative methodologies, including in the model the perceptions and life styles of populations exposed to Schistosoma mansoni. The Federal Government is indicated as the institution to provide the material conditions necessary to form a citizenry with the collective will to control schistosomiasis.

Esquistossomose mansônica no estado da Bahia, Brasil: tendências históricas e medidas de controle

Visando a contribuir para o aperfeiçoamento das estratégias de controle da esquistossomose mansônica, foram estudadas as modificações no padrão de distribuição das prevalências municipais no Estado da Bahia no período de 1950 a 1994, seus determinantes e o efeito da quimioterapia em larga escala. Verificou-se redução da prevalência média de esquistossomose para o estado como um todo, de 15,6% para 9,5%, no período de estudo. Não foram observadas modificações substanciais no padrão básico de distribuição espacial da prevalência. Entretanto, em municípios do oeste, sudoeste e litoral norte do estado, verificou-se aumento da prevalência, indicando o surgimento de novas áreas de transmissão. Comparando-se as variações das prevalências municipais de acordo com a utilização da quimioterapia em larga escala, verificou-se que houve redução na Bacia do Paraguaçu, onde vem sendo intensamente adotada tal medida, em proporção semelhante ao que foi observado para algumas áreas sem quimioterapia. As análises de correlação e regressão utilizadas não evidenciaram associação entre a quimioterapia e a variação da prevalência, observando-se correlações significativas entre esta última variável e a dinâmica populacional. Esses resultados indicam que a redução da prevalência de esquistossomose no estado não pode ser atribuída exclusivamente à utilização de quimioterapia, mas deve contemplar a articulação com os fatores relacionados à organização do espaço, que contribuem para diminuir o risco de transmissão. A forma incompleta e espacialmente desigual que caracteriza o processo de urbanização, aliada à intensa mobilidade da população, possibilita a disseminação da esquistossomose mansônica para novas áreas de transmissão, como evidenciado no Estado da Bahia.

A municipal level approach to the management of schistosomiasis control in Peri-Peri, MG, Brazil

A schistosomiasis control program was implemented between 1974/87 in Peri-Peri, MG (622 inhabitants). Molluscicide (niclosamide) was applied at three monthly intervals in water sources with Biomphalaria glabrata, and individuals eliminating Schistosoma mansoni eggs in the feces were treated annually with oxamniquine. From 1974 to 1983 the control measures were undertaken by staff of the "René Rachou" Research Center FIOCRUZ (CPqRR), and from 1984 to 1987 these measures were included in the Capim Branco basic health network activities. During both periods, the prevalence, incidence, intensity of infection and hepatosplenic form as well as the number of infected snails decreased significantly. The prevalence decreased from 43.5 to 4.4%, the incidence from 19.0 to 2.9%, the overall intensity of S. mansoni from 281 to 87 and of the hepatosplenic form from 5.9 to 0.0%. The results obtained suggest that the municipal management of control measures was as effective as the vertical program conducted by CPqRR staff.

The prolonged use of niclosamide as a molluscicide for the control of Schistosoma mansoni

Applications of niclosamide at three-monthly intervals were undertaken for 14 years in foci of Biomphalaria glabrata in the water sources of Peri-Peri (Capim Branco, MG). All the residents of the area were submitted to an annual fecal examination (Kato/Katz) and those individuals eliminating Schistosoma mansoni eggs were treated with oxamniquine. A malacological survey was undertaken at three-monthly intervals by means of ten scoops with a perforated ladle each ten metres along the two banks of the ditches and streams of the region. Where snails were found, molluscicide was applied by means of dripping or aspersion using a 3 ppm aqueous suspension of niclosamide. Initially, a mean of 14.3% of snails in the region were found to be eliminating cercariae. Following the first four applications of molluscicide, this was reduced to 0.0% and maintained at about 1.5% throughout the program. Thus, there was a continued possibility of schistosomiasis transmission in the area and it was observed that the population of snails reestablished itself within three months of molluscicide application. The results obtained in this study do not encourage the continual use of niclosamide as the only method of control of schistosomiasis.

Spontaneous reduction in Schistosoma mansoni infection in endemic communities of the lake Tana basin, north-western Ethiopia

The prevalence and intensity of Schistosoma mansoni infections were studied in 3 endemic communities in north-western Ethiopia using the Kato-Katz stool examination technique to determine changes in the epidemiology of schistosomiasis in the absence of control programmes. The prevalence declined in Chwahit community by 21.6%, and in the villages of Jenda and Guramba by 43.2 and 100% respectively in the course of 15 years. This spontaneous reduction in schistosomiasis is perhaps the result of recurrent drought in the area. This finding has implications for public health programmes in the area and intervention measures against schistosomiasis.

Water-contact patterns and Schistosoma mansoni infection in a rural community in northeast Brazil

We evaluated the influence of water-related human activities, contaminative behaviour, house location, education and socio-economic status on endemic Schistosoma mansoni infection. The study was conducted in a hilry non-irrigated area of rural northeast Brazil amongst a defined population of subsistence farmers, of whom 93% were infected by age 20. The area was mapped, water bodies were surveyed, and a detailed questionnaire was performed on each household. Infection was assessed by duplicate stool examinations using the sensitive Bell technique to quantify egg excretion. For each household, and index of intensity of infection was computed by grouping individual log-transformed egg counts as an age-sex adjusted Z score. Few households had a sanitary installation or a domestic water supply. However, neither water-contact nor contaminative behavior were indiscriminate. The people made considerable effort to defaecate far from a water source, to obtain household drinking water from the cleanest source, and to bathe only at certain sites where privacy is assured. Land ownership and literacy correlated poorly with the household index of intensity of infection. The key influence on infection status was the relative location of the house and snail-free or snail colonized water sources. In this area, a safe domestic water supply is the critical input needed to achieve definitive control of endemic Schistosomiasis.

[Epidemiological importance of wild animals in schistosomiasis mansoni]

Com o intuito de averiguar a importância de alguns roedores como possíveis reservatórios do S. mansoni, na ausência do homem parasitado, foi realizada pesquisa, visando contribuir para o esclarecimento de aspectos ligados à cadeia epidemiológica da esquistossomose, bem como conhecer alguns parâmetros da biologia de certos roedores, em seu habitat semi-natural. O experimento foi realizado num viveiro de 952 m², no município de Taubaté, São Paulo (Brasil), numa área endêmica de esquistossomose mansônica humana, e teve a duração de três anos e seis meses (agosto de 1973 a dezembro de 1976). Foram utilizados como hospedeiros definitivos, Holochilus brasiliensis leucogaster, Zygodontomys lasiurus, Oryzomys nigripes eliurus e Cavia aperea aperea; como hospeideiro intermediário, Biomphalaria tenagophila e posteriormente B. glabrata. Entre agosto de 1973 e janeiro de 1976, não houve encontro de B. tenagophila eliminando cercárias de S. mansoni; não se verificou, também, infecção natural de roedores. Em agosto de 1975, houve introdução acidental de desovas da B. glabrata, cujos adultos, em 1976, apresentaram infecção por S. mansoni em três ocasiões, com índices de 2,0; 1,6 e 0,8%. No mesmo ano de 1976, dois Holochilus, nascidos no Viveiro, eliminaram ovos viáveis de S. mansoni. Foi possível obter dados de 41 H. b. leucogaster, 28 introduzidos e 14 nascidos no local. O exemplar que sobreviveu mais tempo completou 346 dias. Os animais nascidos no Viveiro e capturados pela primeira vez pesavam, em média, 20 a 50 g. Notou-se que o peso corporal aumentou com o tempo e parece não estacionar até a morte do animal. Z. lasiurus e C. a aperea não procriaram e nem adquiriram infecção ao S. mansoni. O. n. eliurus, procriou e permaneceu vivo, em média, menos de 100 dias; não foi observada eliminação de ovos do parasita. É pouco provável que H. b. leucogaster e B. tenagophila mantenham o ciclo da esquistossomose na ausência da contaminação humana, na natureza. Porém, é possível que, futuramente, H. b. leucogaster na presença de B. glabrata, possa servir de reservatório da esquistossomose, na natureza, quando encontrados em abundância e desde que adaptados com cepas adequadas do parasita.

Roedores silvestres na epidemiologia da esquistossomose mansônica no lago da Pampulha, Belo Horizonte, Minas Gerais (Brasil)

Entre julho/1972 e novembro/1973, tiveram prosseguimento investigações relacionadas ao problema da esquistossomose mansônica no Lago da Pampulha, Belo Horizonte, MG (Brasil), particularmente sobre o papel epidemiológico dos roedores no problema local daquela parasitose. Dentro do período mencionado, foram realizadas 58 capturas, obtendo-se 183 exemplares de roedores, pertencentes a 8 gêneros e 10 espécies distintas. Através de exames de fezes e de vísceras (fígado e intestino) verificou-se que 10,9% (20) dos espécimens capturados abrigavam ovos e vermes adultos de Schistosoma mansoni. Apenas 3 espécies encontravam-se parasitadas: Holochilus brasiliensis (Desmarest, 1818), Nectomys squamipes squamipes (Brants, 1827) e Zygodontomys lasiurus (Lund, 1841), com, respectivamente, 11 (55,0%), 6 (30,0%) e 3 (15,0%) exemplares infectados. Não obstante, ao longo de cerca de 21 km de perímetro do lago, em 16.090 conchadas apenas 0,4% (70) revelaram-se positivas para planorbíneos, sendo capturados 64 exemplares de Biomphalaria glabrata (Say, 1818) e 35 de B. tenagophila (d'Orbigny, 1835), todos negativos para cercárias de S. mansoni. O encontro de roedores parasitados decorreria da eliminação de cercárias por planorbíneos existentes nos córregos tributários e valas a eles adjacentes. As larvas do trematódeo, levadas pela correnteza, atingiriam os roedores no "domínio vital" adstrito ao lago. Através de mecanismo análogo, os usuários do lago poderão se infectar, malgrado a permanente vigilância das autoridades sanitárias locais, que patrocinam estudos destinados à recuperação daquele local. Admitem, finalmente, os AA. que o papel dos roedores na epidemiologia da esquistossomose variará, sempre, de uma área para outra, segundo características de cada ecossistema envolvido.

Immunological control of schistosomiasis

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