True about Giardia is -

Option 1 Agents of Traveller's diarrhea: Enterotoxigenic Escherichia coli (10-45%)- Single most impoant agent Enteroaggregative E. coli (5-35%)- Emerging enteric pathogen with worldwide distribution Campylobacter jejuni (5-25%)- More common in Asia Salmonella- Common in India Others- Aeromonas, Plesiomonas, and Vibrio cholerae Norovirus (< 10%) - Associated with cruise ships Rotavirus (< 5%) - Common among children Parasites (0-10 %): Giardia lamblia, Cryptosporidium, Entamoeba histolytica, Cyclospora Option 2, 3 GIARDIA LAMBLIA: Habitat:mainly Inhabits Mucosa of duodenum and upper ileum of man. Morphology: 2 forms: Trophozoite and Cyst Infective stage: Cyst Route of infection: Feco-oral route. Giardia may also cause traveler's diarrhea. Predisposing conditions to giardiasis are a gammaglobulinemia, common variable immunodeficiency and selective IgA-deficiency.