Multihost Transmission of Schistosoma mansoni in Senegal, 2015-2018

Abstract

In West Africa, Schistosoma spp. are capable of infecting multiple definitive hosts, a lifecycle feature that may complicate schistosomiasis control. We characterized the evolutionary relationships among multiple Schistosoma mansoni isolates collected from snails (intermediate hosts), humans (definitive hosts), and rodents (definitive hosts) in Senegal. On a local scale, diagnosis of S. mansoni infection ranged 3.8%-44.8% in school-aged children, 1.7%-52.6% in Mastomys huberti mice, and 1.8%-7.1% in Biomphalaria pfeifferi snails. Our phylogenetic framework confirmed the presence of multiple S. mansoni lineages that could infect both humans and rodents; divergence times of these lineages varied (0.13-0.02 million years ago). We propose that extensive movement of persons across West Africa might have contributed to the establishment of these various multihost S. mansoni clades. High S. mansoni prevalence in rodents at transmission sites frequented by humans further highlights the implications that alternative hosts could have on future public health interventions.

Keywords: Biomphalaria pfeifferi; Lac de Guiers; Mastomys huberti; One Health; Rodentia; Schistosoma; Schistosoma mansoni; Senegal; Senegal River Basin; West Africa; children; definitive host; evolution; infectious diseases; molecular epidemiology; multihost system; parasites; reservoir; rodents; schistosomiasis; snail; transmission; zoonoses.

Figure

Phylogenetic analysis and geographic locations of Schistosoma mansoni lineages isolated from both humans and rodents (colored silhouettes) or from a single definitive host (black silhouettes), Senegal. Rodent silhouettes represent Mastomys huberti mice or Arvicanthis niloticus rats and snail silhouettes represent Biomphalaria pfeifferi snails (intermediate host). A) Bayesian tree made by using a strict molecular clock and the concatenated mitochondrial 12S rRNA and 4 protein-coding mitochondrial DNA gene sequences. Schistosoma rodhaini and S. mansoni samples from school-aged children in Uganda were included in the analysis. Posterior probabilities and 95% highest posterior density intervals (blue rectangles) are indicated for each node. Branches with nodal support <90% were collapsed. For complete tree, see Appendix Figure 5. B) Geographic locations of multihost S. mansoni lineages, Richard Toll and Lac de Guiers regions. Satellite imagery from Sentinel Hub (Sinergise, https://www.sentinel-hub.com) was used as the base layer. DJ, Didjiery; GA, Ganket; KS, Keur Momar Sarr; MB, Mbane; ND, Nder; RT, Richard Toll; TE, Temeye.