Towards a better understanding of the tripartite interactions driving Schistosoma transmission in Senegal

Snail-borne diseases are caused by trematode parasites and affect more than 300 million people worldwide, while also affecting wildlife and livestock (Hotez et al., 2014; WHO, 2020). The most important of these diseases is schistosomiasis. Despite the availability of adequate tools for diagnosis and treatment and the concerted control efforts to date, schistosomiasis continues to (re-) emerge with unexpected distributions and unprecedented intensities. Here, we will focus on an extraordinary case of shifting disease dynamics that was documented for schistosomiasis in the north of Senegal. After the construction of a dam to embank the Senegal River Basin (SRB) in the 1980s, an important outbreak of intestinal schistosomiasis occurred. This form of schistosomiasis is caused by Schistosoma mansoni, which uses Biomphalaria pfeifferi as intermediate host. Years later, urinary schistosomiasis also emerged in the area. This form of the disease is caused by Schistosoma haematobium, which uses Bulinus globosus and Bulinus truncatus as intermediate hosts. Nowadays, the urinary form is dominant, while intestinal schistosomiasis almost disappeared in some places. To better understand disease dynamics, we need to uncover the processes that shape natural parasite communities within the snail host populations. The first aim is to investigate whether the diminution of prevalence of intestinal schistosomiasis in the Senegal River Basin (SRB) is related to the interactions between Schistosoma mansoni and other parasite species within Biomphalaria pfeifferi. For this, the high throughput amplicon sequencing (HTAS) approach used by Hammoud et al. (2022) needs to be adapted to generate molecular profiles for snails and their trematode parasites with an increased scalability and improved cost-efficiency. We also aim at characterizing the microbiome and trematode communities of the snails Bulinus globosus and Bulinus truncatus sampled along the SRB to assess the influence of host genetics, host microbiome and trematode infections on the susceptibility of B. truncatus and B. globosus towards schistosome infection.