02673nas a2200229   4500000000100000008004100001100002100042700001100063700001600074700001600090700000900106700001100115700001600126700001300142700001200155245015100167856007900318300001300397490000600410520201300416022001402429       2015                            d1 aVan den Broeck F1 aMaes G1 aLarmuseau M1 aRollinson D1 aSy I1 aFaye D1 aVolckaert F1 aPolman K1 aHuyse T00aReconstructing colonization dynamics of the human parasite schistosoma mansoni following anthropogenic environmental changes in northwest Senegal.  uhttp://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0003998   ae00039980 v93 a<p><strong>BACKGROUND: </strong>Anthropogenic environmental changes may lead to ecosystem destabilization and the unintentional colonization of new habitats by parasite populations. A remarkable example is the outbreak of intestinal schistosomiasis in Northwest Senegal following the construction of two dams in the '80s. While many studies have investigated the epidemiological, immunological and geographical patterns of Schistosoma mansoni infections in this region, little is known about its colonization history.</p>

<p><strong>METHODOLOGY/PRINCIPAL FINDINGS: </strong>Parasites were collected at several time points after the disease outbreak and genotyped using a 420 bp fragment of the mitochondrial cytochrome c oxidase subunit 1 gene (cox1) and nine nuclear DNA microsatellite markers. Phylogeographic and population genetic analyses revealed the presence of (i) many genetically different haplotypes at the non-recombining mitochondrial marker and (ii) one homogenous S. mansoni genetic group at the recombining microsatellite markers. These results suggest that the S. mansoni population in Northwest Senegal was triggered by intraspecific hybridization (i.e. admixture) between parasites that were introduced from different regions. This would comply with the extensive immigration of infected seasonal agricultural workers from neighboring regions in Senegal, Mauritania and Mali. The spatial and temporal stability of the established S. mansoni population suggests a swift local adaptation of the parasite to the local intermediate snail host Biomphalaria pfeifferi at the onset of the epidemic.</p>

<p><strong>CONCLUSIONS/SIGNIFICANCE: </strong>Our results show that S. mansoni parasites are very successful in colonizing new areas without significant loss of genetic diversity. Maintaining high levels of diversity guarantees the adaptive potential of these parasites to cope with selective pressures such as drug treatment, which might complicate efforts to control the disease.</p>
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