Schistosomiasis, also known as bilharzia, is a neglected tropical disease (NTD) caused by trematode parasites of the genus Schistosoma, transmitted by snails that serve as intermediate hosts.^1,2 The World Health Organization (WHO) estimated that as of 2023, schistosomiasis affected approximately 240 million people worldwide and 85% of infections were in underdeveloped areas of sub-Saharan Africa.^3,4 In South Africa, 4 million people are at risk of contracting schistosomiasis, mostly children living in underserved communities.^4,5,6 Furthermore, a study conducted in South Africa reported an average of 36 people per 100 000 infected with schistosomiasis annually between 2011 and 2018.⁶ South Africa is considered moderately endemic for schistosomiasis, with its sub-tropical climate providing suitable habitats for certain snail species in certain regions.⁷ The disease has been reported in the provinces of Limpopo, Mpumalanga, parts of Gauteng, KwaZulu-Natal, and the Eastern Cape.^1,4

Two forms of the disease commonly exist in humans: namely, intestinal schistosomiasis caused by Schistosoma mansoni and Schistosoma japonicum, and urogenital schistosomiasis caused by Schistosoma haematobium, which is more common.^1,8 It is considered a disease of poverty,⁹ common in areas with inadequate water and sanitation, and is the second most fatal parasitic disease.^1,4 Transmission occurs when infected snails release schistosomes into freshwater, which can penetrate human skin upon contact with water.^1,4 Infected humans can further contaminate freshwater by shedding schistosome eggs in urine and faeces. Activities such as swimming, bathing, farming, fishing, river washing and other water-related activities increase one’s exposure to infection.^3,10

The disease can lead to severe, irreversible and potentially fatal complications. Reinfection has been associated with intestinal morbidity and urogenital disorders such as bladder fibrosis, hydronephrosis and an increased risk of bladder cancer in S. haematobium infections.^4,11 S. mansoni and S. japonicum infections can result in periportal fibrosis, portal hypertension and splenomegaly – all of which are considerably life-threatening.⁴ It has also been noted to increase susceptibility to human immunodeficiency virus (HIV) among women because of genital lesions in female genital schistosomiasis.^11,12 In children, Schistosoma infection can contribute to malnutrition, anaemia, cognitive dysfunction and growth inhibition.^2,6 This leads to disrupted school attendance, classroom attendance and long-term psychosocial effects in children.

Schistosomiasis is a category 2 Notifiable Medical Condition (NMC) in South Africa, requiring notification within seven days of diagnosis by healthcare professionals and diagnostic laboratories.¹³ Schistosomiasis is underreported because of its dependence on laboratory detection, which is reliant on patients actively seeking healthcare.⁶ This results in an underestimation of the burden of disease in the country.

Despite schistosomiasis being previously reported in Gauteng, its prevalence and trends in the province are not well understood. Studies have explored aspects of the disease nationally and in other parts of the country where it is prevalent. However, very few studies have information on the disease in Gauteng Province.^6,14 Furthermore, no studies have focused solely on the province by exploring its epidemiological trends to provide necessary locally relevant public health recommendations.

The WHO strategy to prevent and control schistosomiasis includes preventative chemotherapy through mass drug administration to at-risk populations alongside efforts to provide safe water access, adequate sanitation, health education and snail control, with the overall aim of reducing transmission of the disease as well as morbidity resulting from the disease.^3,10,15 Schistosomiasis has been eliminated successfully in countries such as Japan, Tunisia and some parts of the Caribbean through extensive public health efforts implementing the WHO strategy to prevent and control the disease.¹⁶ While other countries such as China and Egypt have made significant progress in controlling the disease and moving towards ultimate elimination, it remains a public health problem in South Africa.^6,10 In order to identify populations at risk and to inform public health action in Gauteng Province, studies exploring the different aspects of the disease need to be conducted.

This study aimed to investigate the epidemiology of human schistosomiasis in Gauteng Province from 2017 to 2022 by describing the demographic characteristics of human schistosomiasis cases determining the trends in human schistosomiasis cases in the province, and estimating the provincial prevalence of schistosomiasis.

There were 2526 human schistosomiasis cases in Gauteng Province from 01 January 2017 to 31 December 2022. The median age of cases was 28 years (IQR: 19–42), and 22.0% (n = 556/2526) of the cases were in the 20–29 years age group. Most of the cases were male (59.5%; n = 1504/2526). The City of Tshwane Metropolitan had the most cases (42.8%; n = 1081/2526) in the province, followed by Ekurhuleni Metropolitan (26.3%; n = 663/2526). Public health facilities reported 77.5% (n = 1959/2526) of the cases. Regarding case classification, 73.7% (n = 1861/2526) were laboratory notifications. Diagnostic testing confirmed 96.0% (n = 2425/2526) of cases through laboratory methods. Of all cases, 14.0% (n = 354/2526) were treated as outpatients, and the case fatality ratio was 0.2% (n = 5/2526) (Table 1).

Men of the 10–19-year age group had the highest (384) number of cases, followed by men of the 20–29-year age group (310) (Figure 1).

Gauteng Province experienced the highest number of human schistosomiasis cases (n = 582) in 2019 and the lowest (n = 208) in 2021. There was a mean of 421 cases per year and an overall declining trend of 37 cases per year between 2017 and 2022 (Figure 2).

The highest number of cases was reported in February 2020 (n = 74), followed by September 2019 (n = 73). Seasonal peaks in case numbers were observed in February–March and August–September across most years (Figure 2).

Gauteng Province experienced the highest human schistosomiasis incidence rate in 2019 (3.8 cases per 100 000 persons). The year with the lowest incidence rate was 2021 (1.3 cases per 100 000 persons). The average provincial incidence rate was 2.8 cases per 100 000 persons between 2017 and 2022 (Figure 3).

The overall prevalence of human schistosomiasis in Gauteng Province was 15 cases per 100 000 between 2017 and 2022. The regions in the province with the highest human schistosomiasis prevalence estimate were Mogale City and City of Tshwane Metropolitan (27 cases per 100 000). The Midvaal region had no cases (Figure 4).

Schistosomiasis remains an NTD of public health concern in South Africa, particularly in disadvantaged communities with inadequate access to water and sanitation. This study aimed to describe the epidemiology of human schistosomiasis to assess trends, geographic distribution and demographic characteristics of reported cases, particularly in Gauteng Province, where the disease remains under-studied and thus not well understood.

In our study, we found that most of the human schistosomiasis cases were young adults, with a high proportion of cases among men aged 10–19 years. Most of the cases were from the public sector, were confirmed cases, and were treated as outpatients. There was a declining trend in the number of cases over time, as well as an overall decrease in incidence. Most of the cases were from the City of Tshwane Metropolitan, in the northern region of the province. The overall prevalence was 15 cases per 100 000.

Schistosomiasis is predominantly a disease affecting school-aged children, typically those defined as between 7 years and 15 years in South Africa.^4,6,17 In this study, most cases were found in the young adult population aged 20–29 years, rather than school-going children. This could be the result of occupational and/or economic or recreational water-related activities, such as swimming, fishing, and informal work near water streams, in areas where schistosomiasis is more common. While previous literature has reported on children younger than 19 years being infected, reinfection has been a common occurrence even after successful treatment of the first episode.^18,19 This may contribute to a similar prevalence of schistosomiasis between the two age groups (school-aged children and young adults) as seen in our study, suggesting a possible continued exposure to infested water sources, leading to repeated infections over time. Further research is necessary to understand reinfection patterns.

Furthermore, age- and sex-specific trends showed that men aged 10–19 years had more cases. This aligns well with the suggestion that school-going boys in endemic areas are more likely to engage in recreational water-related activities, thus increasing their risk of exposure.⁴ While literature has suggested that women are most affected by schistosomiasis because of their involvement in washing clothes and bathing children in open water sources in lower-income settings,^9,20 our study found that prevalent cases were more in men across most age groups. This finding is similar to previous studies carried out in South Africa, which described a higher prevalence of schistosomiasis in men.^5,6,17,21 Among women, the highest burden was observed in those aged 30–59 years, which is more likely the ages of women partaking in domestic labour involving water contact. These trends support the idea that the risk of exposure may vary by gender and age because of different water contact behaviours. Gender disparities and local differences in prevalence may also be influenced by the Schistosoma species, known to affect men and women differently.²⁰ This highlights the need for exploring the type of species more prevalent in high-burden regions in Gauteng Province to inform targeted control measures.

The study also found that Gauteng Province experienced an overall declining trend in the number of human schistosomiasis cases between 2017 and 2022. This could be the result of the coronavirus disease 2019 (COVID-19) pandemic, as mobility and social activities were restricted, reducing movement during this period, thus reducing exposure to water-related activities. In addition, the pandemic led to widespread disruption in routine public health services and surveillance, which may have affected reporting and ultimately underestimated the incidence. The subsequent increase in cases from 2021 may reflect a resumption of healthcare services and routine surveillance as public health systems began to stabilise.

Monthly trends in our study revealed fluctuations in schistosomiasis cases, with peaks observed in February–March and August–September. These periods coincide with increased water-related activities because of seasonal factors. The early-year peak may be linked to summer rainfall, characteristic of the sub-tropical climate in Gauteng Province, creating favourable conditions for reproduction of snails. The late-year peak could correspond with post-winter warming, leading to an increase in human–water-related activities. This is consistent with evidence suggesting that schistosomiasis prevalence is higher during hot, rainy seasons.^7,12 Lower cases in May–June (early winter) and November–December (early summer) may reflect reduced exposure as a result of colder temperatures or other environmental factors affecting the likelihood of transmission.

Furthermore, our study found that most of the cases were classified as laboratory notifications. This classification is significant within the NMC framework, as laboratory notifications indicate more definitive diagnoses, while clinical notifications represent suspected cases notified by clinicians before laboratory testing. Additionally, in terms of diagnostic methods, almost all cases were confirmed through laboratory testing such as microscopy or antigen detection. Although this is a requirement for schistosomiasis, this finding revealed a gap that exists between diagnostic testing and epidemiological classification. The observed proportion of clinical notifications suggests potential lapses in reporting, which may be a result of delays or a lack of updating case statuses once laboratory results become available. This highlights the need for strengthened surveillance through having complete and accurate reporting of data related to schistosomiasis case records.

City of Tshwane Metropolitan, north of the province, had the highest proportion of schistosomiasis cases in the province and a high region-specific prevalence per 100 000 population. This finding aligns with evidence that northern parts of Gauteng Province are endemic for schistosomiasis.¹. Notably, Mogale City had a high region-specific prevalence (> 25 cases per 100 000) despite contributing relatively few cases to the provincial total. Unlike City of Tshwane and other metropolitan areas, Mogale City has a smaller population, suggesting a high disease burden, possibly because of various environmental, socio-economic, occupational, migration, and healthcare-related factors.

Our study had a few limitations. Firstly, the database used in the study did not include data on socio-economic factors, which could have provided a better insight into understanding drivers of schistosomiasis prevalence in the province. Secondly, the dataset had limited variables, restricting the ability to conduct a risk factor analysis that would provide a clear understanding of exposure-risk associations. Thirdly, a considerable proportion of cases had an unknown age, which may have affected age-specific analysis and interpretation. Despite these limitations, this is the first study to document the epidemiology of human schistosomiasis in Gauteng Province, South Africa.

Schistosomiasis was found to be predominant among young adults and notably present among men of all ages. It was most prevalent in the City of Tshwane district, and there was a general downward trend of cases during this period of the study. We recommend that NTDs such as schistosomiasis be prioritised, with strengthened surveillance and reporting of human schistosomiasis in both public and private healthcare sectors for appropriate public health interventions to control the continued transmission of the disease, known to lead to chronic complications affecting the heart and liver, among others.