R N Platt II et al.1;
1 Texas Biomedical Research Institute, United States
DiscussionHybridization between human and
animal parasites may transfer novel pathogenic traits between species,
increasing virulence, host range and negatively impacting human health. Knowing when and how often these events
occurs is an essential step in achieving optimal health outcomes within a One
Health framework. The human parasitic blood fluke, Schistosoma haematobium infects millions of people across
sub-Saharan Africa. S. bovis, a sympatric and closely related species, parasitizes
livestock. Initial genetic analyses
showed discordance between rDNA and mtDNA markers and indicate that these
species are capable of interbreeding. Laboratory crosses between these species
also suggested few reproductive barriers.
To date, early generation S. bovis X S. haematobium hybrids have not been identified
in studies using microsatellite, genome,
or exome-wide single nucleotide variants. In the samples examined so far,
it appears that hybridization between S.
bovis and haematobium occurred in
the relatively distant past with subsequent selection on introgressed alleles
in S. haematobium. In particular an invadolysin gene of S. bovis origin has reached near
fixation in West African populations of S.
haematobium but is absent in East Africa. Here, we scored 9.6 million
genome-wide, single nucleotide variants in 161 S. bovis and S. haematobium
samples collected from 18 countries across the African continent. Our goals
were to (1) examine hybridization and introgression events within a large-scale,
biogeographic context, (2) more precisely date the admixture event(s), and (3)
identify introgressed regions that may be experiencing ongoing selective
pressures in different populations.