What is the name of the disease caused by Giardia lamblia?

The disease caused by Giardia lamblia is called giardiasis. The organism is now commonly named Giardia duodenalis, while Giardia lamblia and Giardia intestinalis remain widely used synonyms for the same human-infecting protist.

Giardiasis usually affects the small intestine and spreads by the fecal–oral route. People become infected by swallowing hardy Giardia cysts in contaminated water, food, or through close contact with an infected person or animal. After ingestion, cysts release active trophozoites, which attach to the intestinal lining and multiply; new cysts are then passed in stool.

Symptoms can include watery or greasy, foul-smelling diarrhea, gas, abdominal cramps, nausea, fatigue, weight loss, and malabsorption. Some infected people have no symptoms. Illness often begins one to three weeks after exposure and may last weeks or longer without treatment.

Giardiasis is sometimes called “beaver fever,” especially in North America, because untreated wilderness water can carry Giardia. Toxoplasmosis, cryptosporidiosis, and amebiasis are different parasitic diseases caused by different organisms.