The Facts
Giardiasis is an intestinal infection caused by a microscopic, single-celled parasite known as Giardia lamblia. A parasite is an organism that lives on or inside another organism called the host. Typically found in lakes, streams, or ponds that have been contaminated by human, muskrat, dog, or beaver feces, giardiasis is also known as "beaver fever."
Giardiasis has been identified as the leading cause of water-borne infections in the United States with about 44,000 cases each year. Higher numbers of infections are seen in the late summer months and even a few deaths have been reported. Travelers to regions of Africa, Asia, and Latin America where clean water supplies are low are at increased risk of contracting the infection.
Some healthy people do not get sick from Giardia lamblia, however they can still pass the infection on to others. Children, seniors, and people with long-term illnesses may be more prone to contracting the illness as the risk of transmission is higher in daycare centers and seniors' residences.
Causes
The parasite that causes giardiasis lives in the intestines of infected humans and animals. It enters the soil, water, food, or other surfaces after bowel movements. The most frequent method of infection is by drinking contaminated water. However, people may also become infected through hand-to-mouth transmission. This involves eating contaminated food or touching contaminated surfaces and unknowingly swallowing the parasite.
The parasites produce cysts (resistant forms of the parasite), which are swallowed. The cysts then reproduce in the intestines causing the signs and symptoms of giardiasis. The parasites then form new cysts, which are passed in the stool continuing the life cycle of the parasite. Ingestion of as little as 10 cysts is enough to cause illness.
