Blastocystis sp. is an enteric protozoan that frequently colonizes humans and many animals. Despite impacting on human health, data on the prevalence and subtype (ST) distribution of Blastocystis sp. remain sparse in Africa. Accordingly, we performed the first multicenter and largest epidemiological survey ever conducted on Blastocystis sp. for this continent. A total of 731 stool samples collected from healthy school children living in 10 villages of the northwestern region of Senegal were tested for the presence of Blastocystis sp. by real-time polymerase chain reaction followed by subtyping of positive samples. Considerable variation in prevalence between villages (51.7 to 100%) was evident with the overall prevalence being 80.4%. Mixed infections were identified in 23% of positive individuals. Among 453 school children with a single infection, ST2 was predominant, followed by ST1, ST3, ST7, ST10, and ST14; this is the first report of ST10 and ST14 in humans. Genetic polymorphisms were evident at the intra-ST level with the identification of numerous ST1 to ST3 genotypes. ST1 showed the greatest intra-ST diversity followed by ST2 and ST3. The prevalence and distribution of STs and genotypes varied among target villages, pointing to several potential infection sources, including human-to-human, zoonotic, and waterborne transmission.

Background/Objectives: Following previous successful Phase I clinical trials conducted in men and women in a non-endemic area for schistosomiasis in Brazil, the Sm14 vaccine was evaluated in an endemic region in Senegal. We report successful clinical trials in adults (Phase IIa) and school children (Phase IIb), respectively, of a Schistosoma mansoni 14 kDa fatty acid-binding protein (Sm14) vaccine + a glucopyranosyl lipid A (GLA-SE) adjuvant. Methods: Participants were evaluated based on clinical assessments, laboratory tests (including hematologic and biochemical analyses of renal and hepatic functions), and immunological parameters (humoral and cellular responses) up to 12 months after the first vaccination dose in the Phase IIa trial and after 120 days in the Phase IIb trial. Results: The results showed strong immunogenic responses and good tolerance in both adults and children, with no major adverse effects. Importantly, significant increases in Sm14-specific total IgG (IgG1 and IgG3) were observed as early as 30 days after the first vaccination, with high titres remaining at least 120 days afterwards. Sm14-specific total IgG serum levels were also significantly enhanced in adults and in both infected and non-infected, vaccinated children and elicited robust cytokine responses with increased TNFα, IFN-γ, and IL-2 profiles. Conclusions: Overall, the Sm14+GLA-SE vaccine is safe and highly immunogenic, with a clearly protective potential against schistosomiasis, supporting progression to the next Phase III clinical trials.