# A reservoir at the gates: nonhuman mammalian hosts for human schistosomiasis in western Africa and the critical challenge for elimination

## TL;DR

The study highlights the role of nonhuman mammals in spreading schistosomiasis in West Africa, complicating efforts to eliminate the disease.

## Contribution

The study identifies nonhuman mammalian hosts as reservoirs for human-infective schistosomes in West Africa, emphasizing the need for integrated control strategies.

## Key findings

- Four West African countries reported an 8% overall prevalence of human-infective schistosome infections in nonhuman mammals.
- Benin had the highest proportion of infected hosts at 50%, while Senegal had the lowest at 5%.
- Bos taurus was the most affected species, serving as a reservoir for hybrid schistosome species.

## Abstract

Schistosomiasis, a snail-borne parasitic disease of public health and veterinary importance in tropical areas, is highly prevalent in sub-Saharan Africa, particularly in West Africa. The World Health Organization (WHO) has established ambitious goals of eliminating schistosomiasis as public health problem or interrupting its transmission by 2030. The zoonotic transmission of schistosomiasis involving nonhuman mammals (NHMs) complicates disease endemicity and hinders the attainment of these objectives. This study synthesized recent trends and the prevalence of human-infective schistosomes (HISs), including Schistosoma mansoni, S. haematobium, S. haematobium × S. bovis hybrids, S. guineensis, and S. intercalatum—across 16 West African countries.

We conducted a systematic literature search from March 25 to April 30, 2025, across PubMed, Scopus, Embase, and Web of Science, to identify studies on HISs (S. mansoni, S. haematobium, S. haematobium × S. bovis, S. guineensis, and S. intercalatum) in NHMs in western Africa. In addition, we manually searched African Journal Online (AJOL) and screened the references of the included articles. The data were organized in Microsoft Excel 2021 and analyzed via GraphPad Prism to identify publication trends, NHM infection incidence, and species-specific positivity rates (with 95% CIs). The spatial distribution of HIS-infected NHMs was visualized with QGIS to pinpoint high-risk areas.

Four countries (Benin, Ghana, Nigeria, and Senegal) reported cases of HIS infection in NHMs with an overall prevalence of 8% (95% CI: 7–9%). Benin had the highest proportion of infected hosts (50%, 95% CI: 40–60%) and Senegal had the lowest proportion (5%, 95% CI: 4–6%). Bos taurus (60% prevalence) was the most affected species and served as a reservoir for S. haematobium × S. bovis hybrids, whereas S. mansoni exhibited an extensive distribution among rodent and primate hosts.

For effective elimination, integrated control strategies—spanning NHM surveillance, snail intermediate host monitoring, and human mass drug administration—must be prioritized. Policy reforms should address zoonotic transmission risks, particularly in high-prevalence zones, to align interventions with the complex ecology of schistosomiasis in West Africa.