<prompt> Giardia lamblia:Is the only flagellate parasite without a cystic stageInfection happens by ingestion of trophozoites in food and waterIs the only protozoan parasite found in the lumen of small intestineMay sometimes invade the blood stream and cause ectopic lesions  <response>: Ans. is c i.e., is the only protozoan parasite found in the lumen of small intestineRef: Harrison, 19the, p. 1930; 18the, p. 1730; D.R. Arora, 3rde, p. 44 Only protozoan found in the small intestine, patient complain of dull epigastric pain, flatulence, and chronic diarrhoea, steatorrhoea, stool is voluminous, foul smelling and contain large amount of mucus, patient loses weight. Enterotest is employed and ELISA test is developed for the detection of Giardia antigen in faeces. 