What is giardiasis? Giardiasis (jee-ahr-dahy-uh-sis) is a diarrheal illness caused by a parasite called Giardia. The Giardia parasite lives in the intestines of infected people and animals and forms an outer shell called a cyst. Giardia cysts can live outside the body for long periods of time. Giardiasis is a parasitic disease caused by the protist enteropathogen Giardia duodenalis (also known as G. lamblia and G. intestinalis), especially common in children and travelers. [3][4] Infected individuals experience steatorrhea, a type of diarrhea with fatty sticky stool; abdominal pain, weight loss, and weakness due to dehydration and malabsorption. [1] Less common symptoms include skin. Giardia (/ dʒiːˈɑːrdiə / or / ˈdʒɑːrdiə /) is a genus of anaerobic flagellated protozoan parasites of the phylum Metamonada that colonise and reproduce in the small intestines of several vertebrates, causing the disease giardiasis. Their life cycle alternates between a binucleated motile trophozoite and an infective, metabolically inert, environmentally resistant tetranucleate cyst. Giardia is a tiny parasite (germ) that causes diarrhea. Giardia can spread easily from one person to another or through water, food, surfaces, or objects. A healthcare provider can prescribe medicine to treat illness caused by Giardia. Causes Giardia infections are caused by the parasite Giardia duodenalis (Giardia for short). A parasite is a type of germ that gets its food from, or at the expense of, its host. Parasites live on or in a host (for example, a person or animal). Giardia is protected by an outer shell called a cyst. This outer shell allows it to survive outside the body for weeks to months (for example, in soil. Find out about giardiasis, an infection of the digestive system caused by tiny parasites called Giardia intestinalis. Giardiasis, also known as a giardia infection, is an intestinal disease marked by diarrhea, cramps, nausea, and bloating. A tiny parasite called Giardia intestinalis causes the infection. To help diagnose giardia infection, also called giardiasis, your healthcare professional is likely to test a sample of your stool. Your healthcare team may ask you for several stool samples collected over a few days. The samples then go to a lab to look for parasites. Giardiasis is an infection in your intestines caused by the Giardia parasite. Symptoms include diarrhea and fatigue. Antibiotics can treat it. Giardia infection, also called giardiasis, is one of the most common causes of disease carried by water in the United States. The parasites can live in streams and lakes, public water supplies, swimming pools, whirlpool spas and wells.