Strongyloides stercoralis and Relatives: Recent Advances in General and Molecular Biology

Abstract

Human strongyloidiasis is a threat to global health, presenting significant challenges in diagnosis and clinical management. The imperative to incorporate strongyloidiasis more fully into control programs for soil-transmitted helminths is increasingly recognized. The unique life cycles of Strongyloides stercoralis and congeneric species contain both free-living and parasitic generations, and transcriptomic methods have recently identified genes of potential importance to parasitism in these worms. Proteomics recently revealed stage-specific secreted proteins that appear crucial to the host–parasite interaction. A comprehensive genome sequencing project for Strongyloides spp. is now nearing completion. Recent technical advances in transgenesis for S. stercoralis and S. ratti, including the first establishment of stable transgenic lines, promise to advance functional evaluations of genes expressed in conjunction with crucial life-cycle events. Studies employing these methods recently bolstered the hypothesis that S. stercoralis uses cellular signaling pathways homologous to three that regulate dauer larval development in Caenorhabditis elegans to regulate morphogenesis and development of its infective third-stage larva. The free-living generation of Strongyloides makes classical genetics formally possible. Recent advances, such as a genetic map of S. ratti and a molecular genetic and karyotypic analysis of sex determination in S. papillosus, will greatly facilitate this approach. Advanced methods for study of chemosensation in C. elegans were recently applied to discover numerous host-attractant molecules that mediate host finding and contact by infective third-stage larvae of Strongyloides spp. Finally, nucleic acid-based diagnostic methods have recently come to the fore as alternatives to parasitological and immunodiagnostic techniques.