Reconstructing colonization dynamics of the human parasite Schistosoma mansoni following anthropogenic environmental changes in northwest Senegal

Schistosoma parasites successfully colonize new regions following the construction of water schemes for power production or agricultural purposes. Here we investigated the colonization history of the human parasite Schistosoma mansoni in Northwest Senegal following the construction of two dams in the `80s. Parasites were collected at several time points following the disease outbreak and their genetic profile was characterized using molecular markers. Our results showed that many genetically different parasites must have been introduced at the onset of the epidemic, which complies with the extensive immigration of infected seasonal agricultural workers from neighboring regions in Senegal, Mauritania and Mali. Furthermore, we showed that parasite transmission occurred over a large geographic distance, which implies that new alleles, like resistance alleles, could spread rapidly in this system. These new insights demonstrate how colonization following anthropogenic environmental changes may lead to genetically diverse parasite populations within a short time span. High genetic diversity is often linked with a stronger potential to cope with selective pressures such as drug treatment, which may complicate efforts to control the disease