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An Overview Giardia lamblia Antigen Detection Microwell ELISA
Summary
Giardia lamblia is the protozoan parasite responsible for the disease giardiasis. Symptoms of acute giardiasis include diarrhea, nausea, weight loss, malabsorption, abdominal cramps, flatulence and anemia. The disease may manifest itself as an acute, chronic or as an asymptomatic infection. Giardiasis is the most prevalent parasitic disease in the United States and is responsible for an estimated 100 million mild infections and 1 million severe infections each year.
The mode of transmission of Giardia is through fecal-oral ingestion of cysts. Epidemics of giardiasis have been documented in day care centers and by drinking contaminated water. Day care centers may be directly or indirectly responsible for 45% of diagnosed Giardia infections in the United States. One study found 54% of the children at a day care center were infected.
Another important source of Giardia infection is among homosexual men. Prevalence rates of 5 to 19% for this population have been reported.
Diagnosis of giardiasis has been done through a number of invasive and non‑invasive techniques. Of the non-invasive techniques, microscopic examination of stools has been the most common. However, this method relies on an experienced technician and subsequent observation of intact organisms. Because of the historically low proficiency of correct microscopic examinations and intermittent excretion of organisms, alternative diagnostic methods have been investigated.
One important alternative has been the development of an antigen capture enzyme linked immunosorbent assay (ELISA) for use with stools. These tests have shown comparable sensitivity to experienced microscopic examinations, are fairly simple to perform and do not require the observation of intact organisms.
Principle of Procedure
During the first incubation, antibodies attached to the wells capture Giardia antigens present in the stool supernatant. The second incubation adds an additional anti-Giardia antibody that “sandwiches” the antigen. The third incubation attaches horseradish peroxidase to the sandwich. After washings to remove unbound enzyme, a chromogen is added which develops a color in the presence of the enzyme complex and peroxide. The stop solution ends the reaction. The reaction may then be read visually or with an ELISA reader. |