Lethal giant larvae (Lgl) is evolutionarily conserved tumor suppressor present in fungi and animals.It plays an essential role in establishing apical-basal cell polarity,cell proliferation,differentiation and tissue organization.Here we report the presence ofLgl gene in the blood fluke Schistosomajaponieum (SjLgl),and the chief distribution of SjLgl protein in the unique surface tegument structure.The expression of SjLgl could be knocked down in the parasite in vitro and in vitro by a short interfering RNA (siRNA):based RNA interference approach with a simple soaking method or by tail vein injection into the infected mice.Additionally,SjLgl:speci -tic siRNA treatment during the infection in mice significantly altered the surface structure of adult worm,and negatively impacted egg hatching rate.These observations implied that Lgl may be explored as a novel target for developing immuno: and/or small moleculE-based therapeutics to control and treat the infections caused by schi -stosome and other flatworms.