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."
Giardia lamblia is one of the most common human parasitic infections in Canada. Higher numbers of infections are seen in the late summer months and even a few deaths have been reported. Travellers 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 centres and seniors' residences.
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 that are passed in the stool, continuing the life cycle of the parasite. Ingestion of as little as 10 cysts is enough to cause illness.
The signs and symptoms of giardiasis usually occur within 7 to 14 days of exposure to the parasite, although symptoms may appear as early as 3 days or as late as 25 days. They frequently include diarrhea, pale greasy stools, stomach cramps, gas, nausea, vomiting, bloating, weight loss, and weakness. Some people may experience explosive, foul smelling diarrhea. Fever, rash, and joint pain are less common. The symptoms usually last for 1 to 2 weeks, but may last as long as 6 weeks.
Individuals who have other illnesses may experience longer-lasting symptoms resulting in complications such as prolonged diarrhea leading to dehydration, further weight loss, and malnutrition. Other complications include arthritis and damage to the cells that line the intestine.
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