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.

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).

Figure 2 Figure 2 Percentage change in the population served and number of tests in 2020 and 2021 by the Schistosomiasis Control Program in Pernambuco, Brazil. Figure 2 Percentage change in the population served and number of tests in 2020 and 2021 by the Schistosomiasis Control Program in Pernambuco, Brazil.

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).

Figure 3 Figure 3 Percentage change in the positivity rate in tests conducted by the Schistosomiasis Control Program in 2020 and 2021 in Pernambuco, Brazil. Figure 3 Percentage change in the positivity rate in tests conducted by the Schistosomiasis Control Program in 2020 and 2021 in Pernambuco, Brazil.

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).

Figure 4 Figure 4 Percentage change in the rate of individuals treated in 2020 and 2021 by the Schistosomiasis Control Program in Pernambuco, Brazil. Figure 4 Percentage change in the rate of individuals treated in 2020 and 2021 by the Schistosomiasis Control Program in Pernambuco, Brazil.

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.