How to Diagnose Giardiasis

Giardiasis is an infection by the protozoa giardia lamblia. It's the most common intestinal parasite in the United States, especially in day care centers, long term care facilities and Native American reservations. Giardiasis is transmitted by ingesting Giardia cysts; ingestion of more than 25 cysts will cause infection. These protozoa emerge from the cysts, multiply and colonize the upper small bowel. The following steps will show how to diagnose giardiasis.

Difficulty:

Challenging

Instructions

1. Expect giardiasis to produce a wide range of symptoms, primarily gastrointestinal (GI) in nature. The initial stage is usually asymptomatic but may cause abdominal cramps, explosive water diarrhea, fatigue, fever and foul-smelling flatus in rare cases. The symptoms subside in three to four days as giardiasis transitions into the subacute syndrome.

2. Observe a gradual onset of symptoms in most patients. The stools become soft and greasy and may alternate with constipation. Upper GI symptoms include abdominal cramping, acid indigestion, bloating, nausea and sulfurous belching.

3. Look for weight loss in most patients, with 10 pounds the average. Anorexia and fatigue also are common and giardiasis may become chronic in patients with failure to thrive or malabsorption syndrome.

4. Take at least three stool samples per day about two days apart and examine them microscopically. The trophozoites can be seen in fresh watery stools but are fragile and break apart rapidly. Trophozoites will not be found in older or semisolid stools.

5. Conduct a test against the cyst or trophozoite antigens. An immunofluorescent antibody assay or capture enzyme-linked immunosorbent assay are the preferred techniques.