Schistosomiasis is one of the most important neglected tropical diseases. Despite effective chemotherapeutic treatments， this disease continues to afflict hundreds of millions of people. Understanding the natural intermediate snail hosts of schistosome parasites is vital to the suppression of this disease. A recently identified genomic region in Caribbean Biomphalaria glabrata snails strongly influences their resistance to infection by Schistosoma mansoni. This region contains novel genes having structural similarity to known pathogen recognition proteins. Here we elaborate on the probable structure and role of one of these genes， grctm6. We characterised the expression of Grctm6 in a population of Caribbean snails， and performed a siRNA knockdown of Grctm6. We show that this protein is not only expressed in B. glabrata hemolymph， but that it also has a role in modulating the number of S. mansoni cercariae released by infected snails， making it a possible target for the biological control of schistosomiasis.