A. Complement Fixation Test.
B. Presence of both cysts and trophozoites in stools.
C. Presence of cysts only.
The organism shown in the picture above represents Giardia lamblia which causes giardiasis.
Watery (nonbloody), foul-smelling diarrhea is accompanied by nausea, anorexia, flatulence, and abdominal cramps persisting for weeks or months. There is no fever.
Diagnosis is made by finding trophozoites or cysts or both in diarrheal stools.
In formed stools (e.g., in asymptomatic carriers), only cysts are seen.
An ELISA test that detects a Giardia cyst wall antigen in the stool is also very useful.
Tests for antibody in the serum are not routinely available.