INTRODUCTION

Schistosomiasis is a parasitic disease that is endemic in 78 countries.¹ It is one of the most common neglected diseases in the world, mainly in poor areas without access to potable water and basic sanitation.¹^,2 It can present in a variety of clinical forms, ranging from asymptomatic to severe and potentially fatal. The magnitude of the number of cases, combined with the severity of the clinical forms, keeps schistosomiasis as a public health problem in many places.¹

Worldwide, the African continent is the most affected, with approximately 230 million cases per year. On the American continent, there are approximately 2.3 million cases per year. Among these countries, Brazil is the most affected, with an estimated 2.1 million cases per year.³ In addition, Schistosoma mansoni is the only species that causes schistosomiasis in South and Central America.⁴ In Brazil, schistosomiasis occurs in all five regions, although it is more prevalent in the northeast.⁵ Of the nine States in the Northeast, six are endemic: Alagoas, Bahia, Pernambuco, Rio Grande do Norte, Paraíba, and Sergipe.⁵ In the State of Pernambuco, there are six areas considered endemic, located in the eastern part of the State.⁶ The high incidence in these areas reflects the social nature of the disease, which more severely affects communities with limited sanitation infrastructure and restricted access to clean water, increasing the vulnerability of the populations exposed.^1,6

The COVID-19 pandemic has overwhelmed health systems around the world, with significant socioeconomic impacts on the various components of these systems.^9,10 As a result, many health services, such as screening and early diagnosis, immunization programs, epidemiologic surveillance, emergency services, health education, and vector control, have been compromised.⁹ This setback has affected the diagnosis and treatment of many neglected diseases, such as dengue,¹¹ tuberculosis,⁹ and schistosomiasis.¹²

Based on the above, this study aims to analyze the impact of the COVID-19 pandemic on the epidemiological indicators of the Schistosomiasis Control Program (PCE, acronym in Portuguese) in an endemic area of Northeastern Brazil in 2020 and 2021.

METHODS

Study design and area

This is a population-based ecological study conducted in the State of Pernambuco, Brazil. The State is politically divided into 184 municipalities and the island of Fernando de Noronha, covering an area of approximately 98,000 km². It had an estimated population of 10 million inhabitants in 2021. It is characterized by social inequalities, with 51% of the population living in poverty.¹³ There are 12 regions of health, six of which are considered endemic.⁶Regions I, II, III, IV, V and XII correspond to Recife, Limoeiro, Palmares, Caruaru, Garanhuns and Goiana, respectively.¹⁴ (Figure 1).

Population and study period

The Schistosomiasis Control Program (PCE) contains statistical data related to the population residing in endemic areas for the disease. The population analyzed in the study is from the six endemic regions for schistosomiasis in the State of Pernambuco. The study was conducted with schistosomiasis cases reported between 2020 and 2021. The pre-pandemic period (2015-2019) was extracted from the same database and served as a comparison parameter, as it has been used in other studies ^{9, 11}. The data collection period was November and December 2023.

Epidemiological indicators from PCE that were analyzed:

1. Population served in the study years: refers to the number of people who received the container for collecting material for examination.

2. Number of examinations performed in the study years: refers to the number of people examined (coproscopy).

3. Positivity rate in the study years: refers to the number of people in whom Schistosoma mansoni eggs were identified during the examination.

4. Percentage of people treated: refers to the number of people treated for schistosomiasis among those who tested positive by coproscopy.

Selection criteria

All cases of schistosomiasis diagnosed in the period from 2020 to 2021 were included. Cases that were closed as diagnostic errors were excluded.

Data source

The data was extracted from the Information System of the Schistosomiasis Control Program (SISPCE) from Pernambuco State Health Department (SES/PE) and available at the Department of Information Technology of the Unified Health System (DATASUS). (http://tabnet.datasus.gov.br/cgi/deftohtm.exe?sinan/pce/cnv/pcebr.def)

The Schistosomiasis Control Program (PCE) was implemented in Brazil in 1975 as the Special Schistosomiasis Control Program (PECE) and was renamed the PCE in the 1980s.¹⁴ The program has the potential to implement measures to control and minimize the spread of the disease, such as the distribution of diagnostic kits and drugs provided by the Ministry of Health for the diagnosis and treatment of all diagnosed positive cases to municipalities.^{15, 16}

Impact of the COVID-19 pandemic on the PCE

To measure the impact of the COVID-19 pandemic on the indicators analyzed, the pre-pandemic period (2015-2019) was considered to calculate the expected value for the years 2020 and 2021. These expected values were compared with the observed values, using the following equations:

Impact in 2020:

Where: 1- The event analyzed is the proportion of positive schistosomiasis cases; 2- The expected value for the year is calculated considering the last five years before the start of the pandemic, as recommended. This model has been used in other studies.¹⁷ Results were presented in absolute numbers and proportions. These analyses were performed using Excel spreadsheets (Microsoft ®) and Qgis (version 2.14.11, Open Source Geospatial Foundation (OSGeo), Beaverton, OR, USA).

Ethical aspects

The study used publicly available secondary data and therefore did not require the approval of a research ethics committee. In accordance with the required ethical standards - Resolutions 466/2012, 510/2016, and 580/2018 of the Ministry of Health.

RESULTS

In the pre-pandemic period, the annual average number of people served in the six health regions studied was 270,239. In 2020, this number decreased to 77,428 (a 71.3% decrease compared to the expected number). A decrease was observed in all regions, with the largest decrease in the Recife region (-87.5%). In 2021, there was an increase in the population served compared to 2020 (19,488 more people). However, when considering the expected value (average of the five years before the pandemic), the decrease was still significant (a 64.1% reduction compared to the expected value) (Figure 2 A and B).

A similar trend was seen in the number of tests performed. The pre-pandemic average was 192,032 tests per year. In 2020, there was a decrease of 73.8%, meaning that 141,676 tests were not performed. In 2021, although 13,985 more tests were performed than in 2020, there was a 66.5% reduction (127,691 fewer tests) compared with the pre-pandemic average (Figure 2 C and D).

The statewide positivity rate was 2.5% in the pre-pandemic period, with the highest rate in the Palmares region (5.4%) and the lowest in Caruaru (0.5%) (Figure 3 A). In 2020, the State's positivity rate decreased to 1.7 (-32%), with the largest decrease in the Garanhuns region (-45.7%) (Figure 3 B). In 2021, the positivity rate increased to 2.3%, although it remained 6.4% below the expected rate (2.5%) (Figure 3 C). In addition, the Recife region showed a positive variation in the rate in the two years evaluated (6.1% in 2020 and 29.8% in 2021) and Garanhuns showed a positive variation in 2021 (53.3%) (Figure 3 B and C).

The State rate of individuals treated was 66% in the pre-pandemic period, with the highest rate in the Garanhuns region (84.6%) and the lowest in Recife (61.1%) (Figure 4 A). In 2020, the rate of individuals treated increased by 5.8% (from 66% to 69.9%) compared to the pre-pandemic period, although heterogeneously among regions (Figure 4 B). In 2021, the treatment rate decreased by 25.1% (from 66% to 49.4%). In addition, the regions of Palmares and Recife showed a positive change in the rate in 2020 (17.5% and 3.3%, respectively) (Figure 4 B). All other regions showed a decrease in both years analyzed (Figure 4 B and C).

DISCUSSION

This study analyzed the impact of the COVID-19 pandemic on the epidemiological indicators of the Schistosomiasis Control Program (PCE, acronym in Portuguese) in an endemic area of Northeastern Brazil. The results showed a significant impact on the population served, the number of tests performed, the positivity rate, and the population treated for schistosomiasis.

According to the Ministry of Health, approximately 1.5 million people in Brazil are exposed to schistosomiasis.¹⁸ Brazilian public policy includes strategies to control this disease, such as parasitological testing of feces to identify infected individuals, followed by treatment with appropriate drugs, as well as the use of molluscicides to control the snail and interrupt transmission in natural and artificial breeding sites.¹⁹

In 2020 and 2021, health systems around the world were directly or indirectly affected by the measures adopted to control the COVID-19 pandemic.^{20, 21} The measures adopted to reduce transmission, such as social distancing and reduced access to health services, combined with the fear of part of the population of contracting the infection during the pandemic led to a significant reduction in activities related to research, detection, and treatment of neglected tropical diseases in Brazil.^{12, 20, 21}

In Brazil, as in other countries, clinical suspicions and notifications of diseases such as visceral leishmaniasis,²² leptospirosis,²² malaria,²² and schistosomiasis²² have decreased. Because of the COVID-19 pandemic, the reach of health services has been compromised, which has contributed to a decrease in the number of notifications and confirmed cases of endemic diseases and, consequently, an increase in the case fatality rate.^{5, 22}

A study conducted in another schistosomiasis-endemic area in the Northeast showed that in 2021, there was a 19% decrease in the rate of schistosomiasis in the population analyzed compared to 2019. In that year, only 29.9% of people who needed treatment for the disease were reached, and 43.3% of children with an indication for preventive chemotherapy were treated.¹² It was then observed that PEC activities continuity was affected by the COVID-19 pandemic, causing a reduction in testing, thus reducing the case numbers of the disease, which masked the severity, especially in endemic areas.^{1, 12, 17}

When evaluating the expansion of schistosomiasis treatment coverage in municipalities located in endemic regions of the State, Pernambuco's Annual Management Report (RAG) for 2021 noted low coverage, which was attributed to the redirection of PCE professionals to COVID-19 activities.⁵ A similar situation was observed in the State of Alagoas, where there was a significant decrease in the number of people served.¹²

Because of the consequences of the COVID-19 pandemic, the fight against schistosomiasis requires vigorous action to strengthen the Brazilian health system to ensure timely notification, epidemiologic surveillance, diagnosis, and treatment of the disease.²³ In addition, key control strategies must be implemented, including health education, mass drug administration, intermediate host control strategies, and the implementation of basic sanitation measures.²⁴

Despite all the care taken, this study has limitations, including the fact that it is a population-based ecological study based on secondary data in the public domain. This data is subject to the quality of surveillance services, especially in smaller communities. In addition, the pandemic itself had an impact on these surveillance services and consequently on the quality of the data obtained.

In conclusion, the COVID-19 pandemic has had an impact on the Schistosomiasis Control Program in the State of Pernambuco, with a decrease in the following indicators: population served, rate of tests performed and State positivity rate, especially in 2020. It is recommended that the PCE be strengthened to expand the epidemiological surveillance of the disease, as well as actions that allow early diagnosis and timely treatment of the disease.

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Información adicional

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