Sex‐specific genetic structure in Schistosoma mansoni: evolutionary and epidemiological implications

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Abstract
We studied the population genetic structure of 360 and 1247 adult Schistosoma mansoni using seven microsatellite and seven random amplified polymorphic DNA (RAPD) mark- ers, respectively. Parasites were collected from their natural definitive host Rattus rattus in Guadeloupe (West Indies). We found a sex-specific genetic structure, a pattern never before reported in a parasitic organism. Male genotypes were more randomly distributed among rats than female genotypes. This interpretation was consistent with a lower differentiation between hosts for males relative to females, the higher genetic similarity between females in the same host and the observed local (i.e. within-individual-host) differences in allele frequencies between the two sexes. We discuss our results using ecological and immuno- logical perspectives on host-parasite relationships. These results change our view on the epidemiology of schistosomiasis, a serious disease affecting humans in African and Amer- ican intertropical zones.