Clinical outcomes associated with schistosome infection and alcohol use: a systematic scoping review
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Background
Schistosomiasis and alcohol use are major, co-occurring risk factors for liver disease in low and middle-income countries. However, their interactions and shared disease outcomes remain poorly understood.
Methods
We conducted a systematic review to understand how schistosome infection and alcohol use influence author-defined health outcomes. A systematic search was carried out on 3 March 2025 using the following databases: PubMed (1946 – present), Embase (1974 – present), Web of Science (1964 – present), Global Index Medicus (1901 – present), and Global Health (1973 – present). Quality of studies was assessed descriptively by assessing bias and confounding.
Results
The search yielded 2358 articles, with 21 studies eligible for synthesis. Most studies (76.2%, 16/21) focused on current S. mansoni infection, and the same proportion treated alcohol use as a binary variable. The most reported clinical outcomes were periportal fibrosis (42.9%, 9/21), and biomarkers (19%, 4/21), including serum iron markers. For hepatic outcomes, studies suggested a synergistic association, while for iron-related outcomes, an antagonistic relationship was supported. Cross-sectional studies were most common (66.7%, 14/21), limiting the ability to make assessments on the temporal relationships between exposures and clinical outcomes. Selection bias was the most frequently reported source of bias (28.6%, 6/21), and only four (19%) studies reported both adjusted and unadjusted analyses, allowing for an assessment of confounding.
Conclusions
Co-occurring schistosomiasis and alcohol use is associated with more severe liver pathology, presenting a significant public health concern in endemic areas. Current literature focuses on schistosome-related pathology, where alcohol use acts as a modifying factor. Future research should prioritise longitudinal designs with standardised definitions of alcohol use to better understand interactions between these two exposures for liver outcomes.
AUTHOR SUMMARY
Schistosomiasis is a chronic parasitic disease that is prevalent predominantly in sub-Saharan Africa, but also found in South-East Asia and South America. In these regions, schistosomiasis and heavy alcohol use are two major and frequently co-occurring causes of liver disease. It is currently unclear whether these two exposures cause disease through additive pathways, or whether they interact biologically to accelerate disease progression. This review aims to understand what disease outcomes are caused by concurrent schistosome infection and alcohol use, and their potential biological pathways, as well as to assess the quality of the existing evidence around schistosome and alcohol concurrent exposures. For liver injury, the literature mostly supported an additive effect (perhaps due to independent injury from each exposure). However, there was a lack of studies which can address the temporality of these exposures, and the current literature does not consider the changes in sequence, intensity and duration of schistosome infection and alcohol use. Future studies need to prioritise longitudinal designs which monitor people from childhood, when schistosome infection first occurs, through to adulthood when drinking behaviours develop.
