Prevalence of Schistosoma mansoni and S. haematobium in Snail Intermediate Hosts in Africa: A Systematic Review and Meta-analysis

Abstract

Background. Schistosomiasis is caused by Schistosoma mansoni and S. haematobium in Africa. These schistosome parasites use freshwater snail intermediate hosts to complete their lifecycle. Varied prevalence rates of these parasites in the snail intermediate hosts were reported from several African countries, but there were no summarized data for policymakers. Therefore, this study was aimed to systematically summarize the prevalence and geographical distribution of S. mansoni and S. haematobium among freshwater snails in Africa. Methods. Literature search was carried out from PubMed, Science Direct, and Scopus which reported the prevalence of S. mansoni and S. haematobium among freshwater snails in Africa. The pooled prevalence was determined using a random-effect model, while heterogeneities between studies were evaluated by I2 test. The meta-analyses were conducted using Stata software, metan command. Results. A total of 273,643 snails were examined for the presence of S. mansoni and S. haematobium cercaria in the eligible studies. The pooled prevalence of schistosome cercaria among freshwater snails was 5.5% (95% CI: 4.9–6.1%). The pooled prevalence of S. mansoni and S. haematobium cercaria was 5.6% (95% CI: 4.9–6.3%) and 5.2% (95% CI: 4.6–5.7%), respectively. The highest pooled prevalence was observed from Nigeria (19.0%; 95% CI: 12.7–25.3%), while the lowest prevalence was reported from Chad (0.05%; 95% CI: 0.03–0.13). Higher prevalence of schistosome cercaria was observed from Bulinus globosus (12.3%; 95% CI: 6.2–18.3%) followed by Biomphalaria sudanica (6.7%; 95% CI: 4.5–9.0%) and Biomphalaria pfeifferi (5.1%; 95% CI: 4.1–6.2%). The pooled prevalence of schistosome cercaria obtained using PCR was 26.7% in contrast to 4.5% obtained by shedding cercariae. Conclusion. This study revealed that nearly 6% of freshwater snails in Africa were infected by either S. haematobium or S. mansoni. The high prevalence of schistosomes among freshwater snails highlights the importance of appropriate snail control strategies in Africa.

Modulation of the Host Immune Response by Schistosome Egg-Secreted Proteins Is a Critical Avenue of Host–Parasite Communication

“…Schistosoma mansoni (Africa, South America and the Middle East), S. japonicum (Southeast Asia) and S. haematobium (Africa) are the three schistosome species mainly responsible for human disease [ 1 ]. Africa carries the greatest burden of schistosomiasis, accounting for over 90% of global cases, due to the overlapping habitats of both S. mansoni and S. haematobium [ 3 , 4 ]. The highest level of schistosomiasis is reported in Nigeria (29 million cases), which is closely followed by the United Republic of Tanzania (19 million cases) and the Democratic Republic of Congo (15 million cases).…”

Genomic analysis of a parasite invasion: colonization of the Americas by the blood fluke, Schistosoma mansoni

“…In Africa, S. mansoni use Biomphalaria alexandrina, camerunensis, choanomphala, pfeifferi, stanleyi, and / or sudanica as the snail host, none of which are present in the Americas. Instead, these parasites have adapted to using different Biomphalaria hosts, including B. glabrata, B. straminea, and B. tenagophila (Figure 2; Hailegebriel, Nibret, & Munshea, 2020;Kengne-Fokam, Nana-Djeunga, Bagayan, & Njiokou, 2018;Vidigal et al, 2000). We examined exomic SNV data to identify genes and larger regions of the genome under selection at a finer scale and identified 0-5 putative regions of selection from each of the major populations (Table 4).…”

Nucleic acid amplification techniques for the detection of Schistosoma mansoni infection in humans and the intermediate snail host: a structured review and meta-analysis of diagnostic accuracy

“…Preventive chemotherapy using praziquantel is the global recommended strategy for the control of schistosomiasis (WHO, 2002a), but it has become clear that additional complimentary measures will be needed to achieve elimination of the disease (WHO NTDs, 2013). S. mansoni is transmitted by infected, intermediate host snails belonging to the genus Biomphalaria (Hailegebriel et al, 2020). While reliable, accurate and sensitive diagnosis is essential for the control and ultimate goal of schistosomiasis elimination and crucial for the ongoing validation of vaccine candidates in clinical trials (Ogongo et al, 2018).…”