Population Genetics Group meeting edition:45 location:Nottingham date:4-7 January 2012
Schistosoma mansoni is a human endoparasite that affects more than 200 million people worldwide. This digenean trematode has a special aspect of reproduction in that there is an asexual amplification stage in the snail intermediate host, yielding thousands of clonal cercariae that infect the vertebrate final host. Although empirical evidence is still scarce, this feature is likely to affect population genetics of natural schistosome populations. Other important factors are geography and host mobility. Little attention has however been paid to the impact of host-specific factors on the distribution of schistosome strains, although this question is important from both an evolutionary and epidemiological point of view. We therefore assessed the genetic diversity within and between natural S. mansoni populations in Northern Senegal, taking into account the impact of the complex life-cycle characteristics. F-statistics revealed a random parasite distribution (panmixia) that correlated with high host mobility. In addition, we found significantly higher inbreeding values (Fis) for parasite populations within children than those within adults. These results confirm the hypothesis that human hosts function as ‘genetic mixing bowls’, accumulating parasite strains during their lives. Our study provides insight into the epidemiological factors that can influence transmission dynamics and host-parasite coevolution.