title: Inbreeding within human Schistosoma mansoni: do host-specific factors shape the genetic composition of parasite populations?
abstract: The size, structure and distribution of host populations are key determinants of the genetic composition of parasite populations. Despite the evolutionary and epidemiological merits, there has been little consideration of how host heterogeneities affect the evolutionary trajectories of parasite populations. We assessed the genetic composition of natural populations of the parasite Schistosoma mansoni in northern Senegal. A total of 1346 parasites were collected from 14 snail and 57 human hosts within three villages and individually genotyped using nine microsatellite markers. Human host demographic parameters (age, gender and village of residence) and co-infection with Schistosoma haematobium were documented, and S. mansoni infection intensities were quantified. F-statistics and clustering analyses revealed a random distribution (panmixia) of parasite genetic variation among villages and hosts, confirming the concept of human hosts as 'genetic mixing bowls' for schistosomes. Host gender and village of residence did not show any association with parasite genetics. Host age, however, was significantly correlated with parasite inbreeding and heterozygosity, with children being more infected by related parasites than adults. The patterns may be explained by (1) genotype-dependent 'concomitant immunity' that leads to selective recruitment of genetically unrelated worms with host age, and/or (2) the 'genetic mixing bowl' hypothesis, where older hosts have been exposed to a wider variety of parasite strains than children. The present study suggests that host-specific factors may shape the genetic composition of schistosome populations, revealing important insights into host-parasite interactions within a natural system.
authors.affiliation: 1] Laboratory of Biodiversity and Evolutionary Genomics, University of Leuven, Leuven, Belgium [2] Unit of Medical Helminthology, Institute of Tropical Medicine, Antwerp, Belgium.
authors.forename: F
authors.initials: F
authors.lastname: Van den Broeck
authors.affiliation: Unit of Medical Helminthology, Institute of Tropical Medicine, Antwerp, Belgium.
authors.forename: L
authors.initials: L
authors.lastname: Meurs
authors.affiliation: Zoological Institute, University of Basel, Basel, Switzerland.
authors.forename: J A M
authors.initials: JA
authors.lastname: Raeymaekers
authors.affiliation: 1] Laboratory of Biodiversity and Evolutionary Genomics, University of Leuven, Leuven, Belgium [2] Unit of Medical Helminthology, Institute of Tropical Medicine, Antwerp, Belgium.
authors.forename: N
authors.initials: N
authors.lastname: Boon
authors.affiliation: Laboratory of Bacteriology and Virology, Aristide Le Dantec University Hospital, Dakar, Senegal.
authors.forename: T N
authors.initials: TN
authors.lastname: Dieye
authors.affiliation: Laboratory of Biodiversity and Evolutionary Genomics, University of Leuven, Leuven, Belgium.
authors.forename: F A M
authors.initials: FA
authors.lastname: Volckaert
authors.affiliation: Unit of Medical Helminthology, Institute of Tropical Medicine, Antwerp, Belgium.
authors.forename: K
authors.initials: K
authors.lastname: Polman
authors.affiliation: 1] Laboratory of Biodiversity and Evolutionary Genomics, University of Leuven, Leuven, Belgium [2] Unit of Medical Helminthology, Institute of Tropical Medicine, Antwerp, Belgium [3] Section Invertebrates, Royal Museum for Central Africa, Tervuren, Belgium.
authors.forename: T
authors.initials: T
authors.lastname: Huyse
mesh_terms: D000328:Adult; D000367:Age Factors; D000818:Animals; D001499:Bayes Theorem; D002648:Child; D016000:Cluster Analysis; D005260:Female; D014644:Genetic Variation / Q000235:genetics*; D005828:Genetics, Population; D005838:Genotype; D006790:Host-Parasite Interactions / Q000235:genetics*; D006801:Humans; D007178:Inbreeding; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics; D016133:Polymerase Chain Reaction; D012550:Schistosoma mansoni / Q000235:genetics*; D012675:Senegal; D012737:Sex Factors