Genome analysis of the fatal tapeworm Sparganum proliferum unravels the cryptic lifecycle and mechanisms underlying the aberrant larval proliferation

BackgroundThe cryptic parasite Sparganum proliferum proliferates in humans and invades tissues and organs. Only scattered cases have been reported, but S. proliferum infection is always fatal. However, the S. proliferum phylogeny and lifecycle are still an enigma. ResultsTo investigate the phylogenetic relationships between S. proliferum and other cestode species, and to examine the underlying mechanisms of pathogenicity, we sequenced the entire S. proliferum genome. Additionally, S. proliferum plerocercoid larvae transcriptome analyses were performed to identify genes involved in asexual reproduction in the host. The genome sequences confirmed that the S. proliferum genetic sequence is distinct from that of the closely related Spirometra erinaceieuropaei. Moreover, nonordinal extracellular matrix coordination allows for asexual reproduction in the host and loss of sexual maturity in S. proliferum is related to its fatal pathogenicity in humans. ConclusionsThe high-quality reference genome sequences generated should prove valuable for future studies of pseudophyllidean tapeworm biology and parasitism.