Concluding Remarks
Decades of investigations have significantly advanced our understanding of gastropod immunobiology, particularly with respect to digenetic trematodes. From the early studies of snail susceptibility and histological observations of infections, we are now undertaking functional and mechanistic assessments. Rapid progress of the last three decades notwithstanding, several questions remain to be addressed – see Outstanding Questions. The literature on snail– schistosome interactions is currently dominated by the B. glabrata–S. mansoni model, which may not always directly translate into natural snail–schistosome associations, or be relevant to associations of other snail species and their respective parasites. Nevertheless, knowledge gained from studies of this model is important from the standpoint of evolutionary immunology, in terms of the functional capabilities of invertebrate immune systems, and it certainly forms the foundation of further investigation using alternative snail and schistosome species/strains. The B. glabrata model can also provide insight when studying immunological interactions in other snail–trematode combinations. Understanding snail–schistosome compatibility determinants is a prerequisite for novel schistosomiasis control approaches that can exploit the snail. Genomic modification technology, epitomized by the CRISPR/cas9 system, has already been used to modify mosquitos for resistance to Plasmodium infection [97–99]. This system could theoretically be coupled with factors such as BgGRN to drive increased resistance to schistosome infection in snails, or to reduce resistance to another pathogen, thereby reducing snail populations. Coupled with mass drug administration, this could provide the leverage required to achieve sustained control of human schistosomiasis.
