Data from: Inbreeding within human Schistosoma mansoni: do host- specific factors shape the genetic composition of parasite populations?

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

Microsatellite genotypes and host phenotypes

The worksheet “microsatellite genotypes” contains data from individual parasites (S. mansoni larvae) collected in Senegal, genotyped with nine microsatellite loci combined in a single multiplex: L46951, smd25, smd28 and smd89 (Durand et al., 2000); CA11-1 and S9-1 (Blair et al., 2001); smd11, smd43 and sdma28 (Curtis et al., 2001). This dataset represents 1692 parasites from 63 human hosts with at least five out of the nine loci successfully amplified. The worksheet “host phenotypes” contains host phenotypic data from the 63 human hosts. The host variables include gender, village*, liver morbidity (IP score), bladder morbidity (UBS score), Schistosoma mansoni infection intensity (epg**), Schistosoma haematobium infection intensity (ep 10ml**) and circulating anodic antigen (CAA) concentrations (picogram of CAA per mL). village* : Pakh (code 200), Ndieumeul (code 501), Diokhor Takh (code 502) epg**: number of eggs per gram of faeces; ep10ml**: number of eggs per 10 ml of urine

R script written for some of the analyses

This is an R script that was written for some of the analysis, namely: 1) hierarchical f-statistics 2) tests for inbreeding with multilocus heterozygosity and 3) tests for family structure with relatedness estimate

Human host data

Village: location where human host lived. Host: population number that was assigned to the human host. HostIdentifier: code that is linked with that host. SamplingTime: time when parasites were sampled (e.g. Aug-09 or 09-Aug means that parasites were sampled from this host in August 2009. Age: age of the human host. EPG: eggs per gram of feces, i.e. a measure of infection intensity. CoInfectionWithShaematobium: 1 = when human host was coinfected with Schistosoma haematobium, 0 = when human host was NOT coinfected

Microsatellite data from parasites

This data consists genotypes obtained from Schistosoma mansoni parasites that were type at nine microsatellite markers. Each locus (e.g. L46951) is coded by 6 digits (e.g. 169175). Each allele is coded by 3 digits (e.g. 169)