<prompt> Which organism is associated with causation of urinary bladder cancer -E. coliParagonimusSchistosomaClonorchis  <response>: Ans. is c i.e., SchistosomaSchistosomes These flukes trematodes reside in blood of venous plexus at different sites. Three important species are:-i S. haematobium : Veins of vesical pelvic plexuses, less commonly in portal vein and its mesentric branch.ii S. mansani: Mesentric veins draining sigmoido-rectal region inferior mesentric veins.iii S. Japonicum : Mesentric veins draining ilio-caecal region superior mesentric vein. Schistosomes are transmitted by Snails Secondary host to man definitive host. Infective form in snail is cercaria. Eggs of S. hematobium have terminal spine. Eggs of S.mansoni have lateral spine and eggs of S.japonicum have lateral knob. S. hematobium causes bilharziasis urinary schistosomiasis which is characterized by painless terminal hematuria. S. japonicum and S.mansoni cause Katayama fever. Rarerly, S. hematobium can also cause Katayama fever. Fairlys test is an intradermal skin test with cercarial antigen. It is an allergic reaction, positive in all the varieties of schistosomiasis. Schistosoma hematobium is a well known cause of urinary bladder cancer. 