Giardiasis is a diarrheal illness caused by Giardia lamblia after ingestion of Giardia cysts. Once a person has been infected by Giardia, the parasite lives in the intestine and is passed in stool; one bowel movement can release millions of these parasites. Giardia is found in soil, food, water, or surfaces that have been contaminated with the feces from infected humans or animals. Because the parasite is protected by an outer shell, it can survive outside of the body for long periods of time.
Giardia lamblia has become one of the most widespread causes of chronic diarrhea globally. An infection can cause a variety of intestinal symptoms, either acute or chronic, which include diarrhea, gas or flatulence, greasy stools that tend to float, stomach cramps, upset stomach, and nausea. Some people with giardiasis have no symptoms at all. Giardia cysts are still shed in these asymptomatic cases.
Recent studies have found that about 86% of infected patients develop serum antibody against Giardia lamblia. Determination of human anti-giardia antibody may contribute to the aid of clinical diagnosis and understanding of immune responses for each individual.