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

BACKGROUND

Schistosomiasis is caused by and 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 and among freshwater snails in Africa.

METHODS

Literature search was carried out from PubMed, Science Direct, and Scopus which reported the prevalence of and among freshwater snails in Africa. The pooled prevalence was determined using a random-effect model, while heterogeneities between studies were evaluated by test. The meta-analyses were conducted using Stata software, metan command.

RESULTS

A total of 273,643 snails were examined for the presence of and 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 and 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 (12.3%; 95% CI: 6.2-18.3%) followed by (6.7%; 95% CI: 4.5-9.0%) and (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 or . The high prevalence of schistosomes among freshwater snails highlights the importance of appropriate snail control strategies in Africa.