29
ISSN: 2763-5724 / Vol. 05 - n 04 - ano 2025
SCHISTOSOMA MANSONI IN EUNÁPOLIS, BRAZIL: AN INTEGRATED
ANALYSIS OF EPIDEMIOLOGICAL, ENVIRONMENTAL, AND
MALACOLOGICAL DATA
Diana de Lima1
Adma Rita Kirmse Pereira2
Kaio Henrique Paiva Mezete3
Flaelma Almeida da Silva4
Abstract: Schistosomiasis caused by Schistosoma mansoni remains a signicant public health issue
in Brazil, particularly in areas with poor sanitation and frequent exposure to contaminated water
bodies. In the municipality of Eunápolis, located in southern Bahia, historical records of the disease
indicate the persistence of endemic transmission and underreporting in ofcial health information
systems. In this context, the present study aimed to carry out an integrated analysis of epidemiological,
environmental, and malacological data to identify risk factors for the maintenance and possible
reactivation of the schistosomiasis transmission cycle in the region. This is an observational,
cross-sectional study with a quantitative-qualitative approach, conducted between 2023 and 2024.
Secondary data were collected from SINAN, SIAB, and DATASUS, as well as primary data obtained
through physicochemical and microbiological analyses of water samples and malacological surveys
at 11 strategic points in the municipality. The results revealed the presence of fecal coliforms in water
bodies used for bathing and recreation, along with the identication of Biomphalaria snails in areas of
frequent human activity. The analyses highlight the coexistence of environmental and social factors
that contribute to vulnerability to schistosomiasis, underscoring the need for intersectoral control
1 PhD in Environmental Engineering Sciences, CETSC Professor at the Pitágoras Faculty of
Medicine of Eunápolis.
2 Student of the Medicine Course at the Pitágoras Faculty of Medicine of Eunápolis
3 Student of the Medicine Course at the Pitágoras Faculty of Medicine of Eunápolis
4 Master in Education, CETSC Professor at the Pitágoras Faculty of Medicine of Eunápolis.
30
ISSN: 2763-5724 / Vol. 05 - n 04 - ano 2025
actions, improved sanitation, and health education.
Keywords: Schistosoma mansoni. Public health. Sanitation. Environmental indicators. Snails.
Introduction
The relationship between human health and the environment has been shown to be one of
the most relevant interfaces for understanding the processes of illness in contemporary societies.
In particular, the environmental impacts caused by anthropogenic activities have contributed
to the aggravation of water-based diseases, such as schistosomiasis mansoni, which remains a
neglected disease in several regions of Brazil. In this context, environmental health emerges as an
interdisciplinary eld that allows the identication of risk factors associated with sanitary, social, and
ecological conditions, which are fundamental for the formulation of public prevention policies.
According to Philippi Jr. (2005), the environmental problems resulting from the degradation
of natural resources, especially water, cause direct consequences to public health. Water, as an essential
resource for life, is also a vehicle for numerous diseases when contaminated, and its inadequate use
reects inequalities in access and basic sanitation conditions. The transmission of schistosomiasis,
caused by the parasite Schistosoma mansoni, occurs precisely in environments with contaminated
water collections, in which mollusks of the genus Biomphalaria, intermediate hosts of the disease, are
present.
The World Health Organization (WHO, 2013; 2020) estimates that more than 240 million
people worldwide are at risk of contracting schistosomiasis, with most cases occurring in low-income
countries, especially Brazil. According to the Ministry of Health (Brasil, 2014), the disease is still
considered endemic in at least 12 federated units, with a high prevalence in the Northeast Region,
which demands constant attention from surveillance and control services. The persistence of the
disease in urban and rural areas reveals structural aws in the supply of sanitation and epidemiological
surveillance.
31
ISSN: 2763-5724 / Vol. 05 - n 04 - ano 2025
In the State of Bahia, studies indicate that schistosomiasis has presented complex
epidemiological patterns, with cases recorded even in urbanized areas (Cruz et al., 2020). The literature
also indicates that factors such as low education, absence of continued public policies, inadequate use
of water and lack of health education potentiate the transmission of the disease. In municipalities with
disorderly population growth, such as Eunápolis, these conditions can be aggravated by peripheral
urbanization without adequate sanitary coverage.
The transmission of schistosomiasis is directly associated with contact with contaminated
water bodies. According to Neves (2005), this cycle involves the release of eggs in human feces,
which, when they reach water collections, release larvae (miracidia) capable of infecting mollusks
of the genus Biomphalaria. These, in turn, release cercariae, which penetrate the human skin at the
slightest contact with water. This dynamic, according to Coura-Filho et al. (1995), is inuenced by
sociocultural and economic factors, such as work activities, leisure and domestic practices involving
water, showing that the risk is not only biological, but profoundly social.
The present study is justied by the need to identify and map the environmental,
epidemiological and malacological indicators that inuence the occurrence of schistosomiasis in the
municipality of Eunápolis-BA, considering its historical condition as an endemic area. DATASUS
records indicate that, between 2006 and 2007, the municipality showed a signicant increase in
conrmed cases, reaching a peak of 52 cases in 2007. In the recent period, studies by Lima et al.
(2025) report that between 2017 and 2022, 113 new cases were registered, with one death in 2020,
according to data from the Schistosomiasis Control Program (PCE).
The relevance of the study is also due to the absence of recent scientic productions
focusing on schistosomiasis in Eunápolis, making it difcult to develop educational actions and local
surveillance strategies. In addition, the evidence points to a possible underreporting of the disease,
since, in certain years, no cases were recorded, despite the maintenance of environmental risk factors.
This gap can compromise the effectiveness of the actions of the Unied Health System (SUS) and
reinforces the importance of locally-based studies to support technical decisions.
32
ISSN: 2763-5724 / Vol. 05 - n 04 - ano 2025
The research adopts an observational, cross-sectional and quantitative-qualitative approach,
articulating secondary data from SINAN, SIAB and DATASUS with primary data obtained through
water and mollusk collections at 11 points in the municipality, distributed between urban and rural
districts. Physicochemical and microbiological variables of the water were analyzed, such as turbidity,
pH, chlorine, iron, dissolved oxygen, total and fecal coliforms, in addition to the malacological survey
for the detection of the mollusk Biomphalaria sp. Such procedures sought to identify environmental
vulnerabilities associated with the risk of infection.
In this study, incidence and prevalence were calculated based on the estimated population of
Eunápolis between 2017 and 2022. The estimated prevalence in the period was 10 cases per 100,000
inhabitants, while the annual incidence ranged from 38.28 per 100,000 inhabitants in 2018 to only
0.87 in 2022, showing a reduction, but with the risk remaining. The highest concentration of cases
occurred among male adults, especially in the age group of 30 to 49 years, possibly associated with
the recreational and labor use of contaminated water bodies.
Therefore, this article aims to contribute to the strengthening of environmental health
surveillance and schistosomiasis control at the local level, through the systematization of empirical
data and the critical analysis of risk factors present in Eunápolis. The theoretical foundation anchored
in classical and technical authors, such as Neves (2005), Ferreira (2003) and the reports of the Ministry
of Health, supports the understanding of the parasitological, environmental and epidemiological
aspects that permeate the disease cycle. The results intend to support more effective intersectoral
actions, which articulate health, environment and sanitary education.
Methodology
This is an observational, cross-sectional research with a quantitative-qualitative approach,
which integrated secondary data from ofcial health information systems with primary data obtained
through environmental analysis and malacological survey. This methodological combination allowed
33
ISSN: 2763-5724 / Vol. 05 - n 04 - ano 2025
a broader approach to the occurrence of schistosomiasis mansoni in the municipality of Eunápolis-
BA, by considering epidemiological, environmental and biological aspects of the disease cycle.
The quantitative aspect of the research was applied to the analysis of epidemiological data
extracted from the Notiable Diseases Information System (SINAN), the Primary Care Information
System (SIAB), the Mortality Information System (SIM) and the Schistosomiasis Control Program
(PCE), referring to the period from 2017 to 2022. These data supported the calculation of indicators
such as prevalence, incidence and distribution by sex, age group and location of the notied cases of
schistosomiasis in the municipality.
The qualitative component consisted of eld observation and recording of the environmental
and sanitary conditions of the sampled sites, allowing the characterization of risk factors not captured
by the computerized systems.
The research was developed in the municipality of Eunápolis, located in the extreme south
of Bahia, with a total area of 1,179.1 km², belonging to the Microregion of Porto Seguro. Eleven
collection points were selected, covering urban and rural areas: Mundo Novo, Gabiarra, Fazenda
Martins Dam (Gaucha Station), Alecrim II, Dinah Borges I, Encontro das Águas II and III, Dinah
Borges II Dam, Buranhém River, Colonial Park and Gravatá Ecological Park. The selection of sites
was based on criteria of socio-environmental vulnerability, history of recreational use of water
sources, lack of adequate sanitary infrastructure, and reports of conrmed cases in adjacent areas.
The geographic coordinates of each point were recorded by GPS and mapped for territorial analysis
and epidemiological surveillance purposes.
34
ISSN: 2763-5724 / Vol. 05 - n 04 - ano 2025
Figure 1 – Cartography of the Vector Points of Collection of the Research
Source: Field Research, 2024.
For the analysis of water quality, physicochemical and microbiological parameters were
used, as recommended by Ordinance GM/MS No. 518/2004. The physicochemical variables evaluated
were: turbidity, pH, residual chlorine, iron, dissolved oxygen, ammonia, hardness and alkalinity. The
collection was carried out with properly sterilized polyethylene bottles, packed in thermal boxes,
following the protocols described by the American Water Works Association (AWWA, 1970). The
analyses were made by colorimetric comparison, with the use of Ecokit kits.
The microbiological evaluation was performed using the colipapper technique, with plates
containing culture medium that were immersed in the samples and incubated in an acclimatized
incubator for 15 hours, allowing the identication and counting of total coliforms and fecal coliforms
per colony-forming unit (CFU/100ml). This technique was applied in loco with subsequent laboratory
35
ISSN: 2763-5724 / Vol. 05 - n 04 - ano 2025
support for data validation.
The malacological survey took place simultaneously with the collection of water samples.
Active search was used with the use of shells and visual inspection in backwater areas, aquatic
vegetation and surface sediments. According to Neves (2005), the term “malacological” refers to
the study of mollusks, especially in the context of public health, to those that act as intermediate
hosts of parasites of medical importance, such as those of the genus Biomphalaria, transmitters of
schistosomiasis. The collected mollusks were taxonomically identied from morphological keys
and classied according to the transmission potential of schistosomiasis. The specimens were kept
in individual containers to observe the release of cercariae, although the etiological agent was not
identied in the analyzed samples.
Data analysis was performed using Microsoft Excel spreadsheets, through the calculation
of prevalence and incidence (expressed per 100,000 inhabitants), analysis of the relative frequency of
cases by sex, age group and region, in addition to the systematization of environmental and biological
results. The data were organized into tables and graphs, allowing an integrated visualization of the
risk factors at the points investigated.
From an ethical point of view, the study mostly used secondary data in the public domain,
available on the ofcial platforms of the Ministry of Health, and did not imply direct risks to the
privacy of individuals. However, the eld activities involved environmental collection in public spaces
and observation of local water use practices. Therefore, the team followed the principles of Resolution
No. 510/2016 of the National Health Council, which deals with research in the Human and Social
Sciences, and Resolution No. 466/2012, regarding ethics in research with human beings.
Analysis and Discussion of Results
The analysis of epidemiological data regarding schistosomiasis mansoni in the municipality
of Eunápolis, from 2017 to 2022, revealed the persistence of the endemic as a chronic challenge
36
ISSN: 2763-5724 / Vol. 05 - n 04 - ano 2025
to local public health. Although the number of conrmed cases has uctuated over the years, the
occurrence of one death in 2020 and the maintenance of new cases until 2022 show the permanence
of the active transmission cycle in the region, as also observed by Vasconcelos et al. (2023), who warn
of the need for continued surveillance in areas with a history of endemic.
The distribution of cases by sex and age group indicated greater involvement among male
individuals, especially in the group between 20 and 49 years old, coinciding with the ndings of Lima
et al. (2022), which relate this prole to greater exposure to risk environments during work activities.
This pattern highlights the importance of considering the social determinants of the health-disease
process, such as occupation and sanitary conditions, in line with the analyses of Carvalho et al. (2021).
The incidence of cases in urban areas of Eunápolis, such as in the Dinah Borges and
Encontro das Águas neighborhoods, challenges the social imaginary that associates schistosomiasis
exclusively with rural and riverside areas. According to Amaral et al. (2018), the advance of unplanned
urbanization and the precariousness of basic sanitation services are factors that favor the urbanization
of the disease, a reality that was also observed in the present study.
Physicochemical and microbiological analyses carried out at 11 points in the territory
conrmed the presence of fecal coliforms in environments widely used for bathing and recreation.
The presence of fecal coliforms in urban water bodies such as the Dinah Borges I Dam, the Meeting
of the Waters II and III and the Colonial Park suggests a persistent health risk in spaces of collective
use, especially for children and young people. These data conrm the absence of adequate sanitary
infrastructure, as pointed out by Faria and Molevade (2008), when they associate the precariousness of
sanitation with vulnerability to waterborne diseases. This nding is reafrmed by Lima et al. (2025),
who demonstrated, in a recent epidemiological analysis, the relationship between the high incidence
of schistosomiasis and the lack of basic sanitation in the peripheral neighborhoods of Eunápolis,
reinforcing the correlation between precarious infrastructure and continuous exposure to the parasitic
cycle.
In addition to bacteriological contamination, the physicochemical parameters analyzed,
37
ISSN: 2763-5724 / Vol. 05 - n 04 - ano 2025
such as pH, turbidity, dissolved oxygen, and the presence of iron, revealed non-compliance with the
standards established by Ordinance GM/MS No. 888/2021, especially in the samples from Alecrim II
and Estação Gaúcha. These parameters indicate conditions conducive to the maintenance of suitable
habitats for host mollusks, as highlighted by Souza et al. (2021), who highlight the importance of
water quality in the ecology of schistosomiasis.
The presence of Biomphalaria sp., identied at the Dinah Borges I and II points and at
the Gaucho Station, reinforces the vulnerability of these areas and the need for intersectoral control
actions. In addition to the biotic and microbiological factors already discussed, the soil analysis
revealed relevant environmental information to understand the distribution of Biomphalaria sp. in
the springs studied. It was observed that the only two points with conrmed presence of the mollusk,
the Dinah Borges I and II dams, share a common geological characteristic: predominantly clayey
soils with a supercial sandy layer and signicant presence of decomposing organic matter. This
composition facilitates the accumulation of water, creates stable microhabitats and allows the burial
of mollusks during periods of drought, favoring their survival and reemergence during rains
The ndings dialogue with the evidence presented by Costa et al. (2019), which indicate that
the mere presence of the mollusk, even without active infection, already represents an imminent risk
for the reactivation of the parasitic cycle, especially in environments with recreational use of water.
38
ISSN: 2763-5724 / Vol. 05 - n 04 - ano 2025
Graph 1 – Environmental Indicators at the Collection Points – Eunápolis/BA
Source: Field Research, 2024.
The convergence between the presence of mollusks, microbiological contamination and the
frequency of human use of water bodies in Eunápolis reveals a scenario of high socio-environmental
risk. Similarly, Silva et al. (2023) demonstrated that environments where leisure practices, lack of
sanitary infrastructure, and the presence of vectors coexist form critical zones for urban schistosomiasis.
Although some points, such as the Gravatá Ecological Park and the Colonial Park, do not
have the presence of Biomphalaria, the high amount of aquatic vegetation and the decomposition of
organic matter observed in these places make them ecologically favorable to future colonization,
as already discussed by Souza et al. (2021). This nding points to the importance of continuous
monitoring.
Another relevant aspect is the use of water by residents in vulnerable situations, especially
in the Colonial Park, where practices such as bathing and washing clothes were observed, in a total
absence of infrastructure. These data reinforce the argument of Faria and Molevade (2008) that equity
in access to safe water is a fundamental right and a minimum condition for health promotion.
39
ISSN: 2763-5724 / Vol. 05 - n 04 - ano 2025
When considering the socioeconomic prole of Eunápolis, marked by signicant inequalities
and an illiteracy rate of 14.8% in the population over 15 years of age, according to data from the IBGE
(2010), it is understood that living and working conditions contribute to the perpetuation of neglected
diseases, such as schistosomiasis. This analysis converges with the understanding of Costa et al.
(2019) about the social determinants of health as structuring elements of risk.
In addition, the use of contaminated natural resources as a source of supply by water trucks,
identied in the Dinah Borges II Dam, reveals the fragility of public policies for sanitation and water
supply in peripheral urban areas. Such use exposes entire populations to contamination by several
pathogens, in addition to Schistosoma mansoni, as pointed out by Amaral et al. (2018).
This correlation between soil type and vector occurrence reinforces the hypothesis
that the soil quality of the environment is a silent conditioning factor for the maintenance of the
schistosomiasis cycle. According to data from the IBGE and the Government of the State of Bahia,
the clay soils of the municipality of Eunápolis, rich in iron and aluminum, have a soft texture and
high water retention capacity, creating conditions conducive to the reproduction of Biomphalaria.
This environmental aspect, added to the low sanitation coverage, constitutes a complex risk scenario
for local populations, especially in peripheral urban regions where there is greater anthropogenic
pressure on water resources.
In the case of epidemiological surveillance, relevant underreporting was identied in the
analyzed databases, especially in years with a total absence of formal records, which compromises the
effectiveness of control actions. This operational fragility is also highlighted by Lima et al. (2022), who
point to the inconsistency in SINAN data as an obstacle to the formulation of effective intervention
strategies.
The cross-referencing of environmental and biological data with epidemiological records
showed signicant discrepancies. For example, places with critical environmental indicators, such
as Alecrim II and Estação Gaúcha, have not had recent records of human cases, which may be a
reection of the absence of active search and mass coproparasitological tests, as proposed by Costa
40
ISSN: 2763-5724 / Vol. 05 - n 04 - ano 2025
et al. (2019).
The concept of “amplied environmental vulnerability”, used by Faria and Molevade
(2008), helps to understand these contradictions, to the extent that it incorporates the socio-territorial
dimension to the analysis of risks. This allows us to afrm that, in Eunápolis, there are territories
silently exposed to schistosomiasis, even without the visible occurrence of outbreaks.
The literature reviewed and the data obtained converge to the understanding that the
persistence of schistosomiasis in the municipality is due to the combination of ecological factors
(presence of the mollusk and water quality), socioeconomic (poverty, social vulnerability) and
institutional factors (failures in surveillance and public policies).
At the same time, there is divergence among authors as to the emphasis that should be given to
the role of sanitation. While Faria and Molevade (2008) prioritize physical infrastructure, Costa et al.
(2019) defend the centrality of health education and community mobilization as effective instruments
for the transformation of risk practices.
Another point of theoretical tension identied is related to the role of recreational use of
water in the spread of the disease. For Souza et al. (2021), recreation is a central factor in human-
mollusk-parasite contact; for Lima et al. (2022), work activities (such as agriculture) continue to be the
main routes of exposure in rural areas of the Northeast.
In summary, the ndings of this study reinforce the thesis that Eunápolis is experiencing
a process of urbanization of risk, marked by the overlapping of historical vulnerabilities and
new territorial dynamics. This requires intersectoral responses, ranging from urban planning to
environmental health actions and promotion of access to drinking water.
The integrated analysis allowed not only to identify the critical points of schistosomiasis
in the territory, but also to propose a replicable approach to health surveillance that considers local
singularities. This proposal is in line with the recommendations of Vasconcelos et al. (2023) on
territorial models for coping with neglected diseases.
Finally, it is observed that, although the data show a reduction in the absolute number of
41
ISSN: 2763-5724 / Vol. 05 - n 04 - ano 2025
cases, the complexity of the factors involved points to the urgency of new prevention strategies. This
includes strengthening malacological surveillance, improving information systems and, above all,
valuing communities as protagonists in caring for the territory.
References
BAHIA. Superintendence of Economic and Social Studies of Bahia – SEI. Territorial Prole of the
Municipality of Eunápolis. Salvador: SEI, 2020. Available at: https://www.sei.ba.gov.br/. Accessed on:
June 25, 2025.
BRAZIL. Ministry of Health. Ordinance GM/MS No. 888, of May 4, 2021. Establishes the procedures
and responsibilities related to the control and surveillance of the quality of water for human
consumption. Federal Ofcial Gazette: section 1, Brasília, DF, May 5, 2021. Available at: https://
www.in.gov.br/en/web/dou/-/portaria-gm/ms-n-888-de-4-de-maio-de-2021-316818931. Accessed on:
June 15, 2025.
COSTA, S. M. et al. Malacological surveillance as a strategy to control schistosomiasis: a study in
municipalities in the Zona da Mata of Minas Gerais. Brazilian Journal of Tropical Medicine, v. 52,
e20180341, 2019. Available at: https://www.scielo.br/j/rbmt. Accessed on: June 22, 2025.
COURA FILHO, P. et al. Reinfection by Schistosoma mansoni in an endemic area in Brazil. Memórias
do Instituto Oswaldo Cruz, v. 90, n. 4, p. 537–541, 1995. Available at: https://www.scielo.br/j/mioc.
Accessed on: June 27, 2025.
CRUZ, C. M. et al. Prevalence of schistosomiasis and associated factors in riverside communities in
northeastern Brazil. Journal of Public Health, v. 54, p. 1–10, 2020. Available at: https://www.scielo.
br/j/rsp. Accessed on: June 27, 2025.
FARIA, A. M.; MOLEVADE, D. B. Education as a promoter of health and citizenship: an intersectoral
approach. Revista Educação & Saúde, v. 4, n. 2, p. 45–57, 2008.
FERREIRA, H. S. Sanitation and parasitic diseases in peripheral urban communities: a case study.
Revista Brasileira de Epidemiologia, v. 6, n. 2, p. 111–118, 2003. Available at: https://www.scielo.br/j/
42
ISSN: 2763-5724 / Vol. 05 - n 04 - ano 2025
rbepid. Accessed on: June 27, 2025.
IBGE – Brazilian Institute of Geography and Statistics. 2010 Demographic Census: characteristics
of the population and households. Rio de Janeiro: IBGE, 2010. Available at: https://www.ibge.gov.br.
Accessed on: June 22, 2025.
LIMA, D. M. et al. Epidemiological analysis of schistosomiasis in the municipality of Eunápolis (BA):
a descriptive study based on surveillance data from 2017 to 2022. Health and Society, [S. l.], v. 03,
p. 177–199, 2025. DOI: 10.51249/hs.v5i03.2566. Available at: https://periodicojs.com.br/index.php/hs/
article/view/2566. Accessed on: 8 jul. 2025.
NEVES, D. P. Human parasitology. 11. ed. São Paulo: Atheneu, 2005.
PHILLIPS, M. Schistosomiasis and contact with water: patterns of behavior and risk of infection.
Tropical Medicine & International Health, v. 10, n. 10, p. 1.064–1.070, 2005.
SOUZA, L. G. et al. Environmental dynamics and risks of schistosomiasis transmission in urban and
rural areas of Brazil. Cadernos de Saúde Coletiva, v. 29, n. 1, p. 77–84, 2021. Available at: https://
www.scielo.br/j/cadsc. Accessed on: June 22, 2025.
VASCONCELOS, D. M. et al. Territorial planning and schistosomiasis: intersections between health,
environment and public policies. Saúde em Debate, Rio de Janeiro, v. 47, n. 137, p. 250–263, 2023.
Available at: https://www.scielo.br/j/sdeb. Accessed on: June 22, 2025.
WHO – WORLD HEALTH ORGANIZATION. Schistosomiasis: progress report 2001–2011 and
strategic plan 2012–2020. Translated by AI. Geneva: WHO Press, 2013. Available at: https://apps.
who.int/iris/handle/10665/78074. Accessed on: June 27, 2025.
WHO – WORLD HEALTH ORGANIZATION. Guidelines on control and elimination of human
schistosomiasis. Translated by AI. Geneva: WHO Press, 2020. Available at: https://www.who.int/
publications/i/item/9789240015195. Accessed on: June 27, 2025.
