Giardiasis

Question 1

what is giardiasis caused by

Answer 1

Caused by Giardia duodenalis

Question 2

Giardiasis Life Cycle and Infection

Answer 2

1. Infectious cysts are swallowed via contaminated water, food, or faecal-oral transmission (e.g. poor hygiene, close contact).
2. Cysts “hatch” in the small intestine, releasing trophozoites.

Each cyst gives rise to two trophozoites.

3. Trophozoites multiply asexually in the gut lumen
4. As the parasites move to the colon, they re-encyst (form cysts again).
5. Infectious cysts are passed out in faeces → transmission cycle continues.

Question 3

Clinical Diagnosis of Giardiasis

Answer 3

Incubation: ~7–10 days.

Early symptoms:

Belching with “eggy” taste
Bloating, abdominal distension
Nausea, watery and foul-smelling diarrhoea

Chronic symptoms:
Persistent diarrhoea, cramps, weight loss
Malabsorption → nutritional deficiencies
Can affect growth and development (failure to thrive)

More severe in immunocompromised patients

Highly contagious → clusters common (e.g. in families)

Question 4

Giardiasis direct tests

Answer 4

1 Microscopy of Faecal Samples
Used to detect cysts and trophozoites.

2. Direct Fluorescence Assay (DFA)
   Fluorescent antibodies bind to antigens on the cyst wall.
   Examined using a fluorescence microscope.
3. Entero Test (String Test)
   A non-invasive test to retrieve trophozoites from the upper small intestine.

Question 5

Giardaisis: Antigen Detection Tests; Lateral Flow Assay

Answer 5

A one-step immunoassay for detecting Giardia and/or Cryptosporidium antigens in stool.

Tells whether the antigen is present but doesn’t measure quantity.

Question 6

Giardaisis: Antigen Detection Tests; ELISA (Enzyme-Linked Immunosorbent Assay)

Answer 6

Detects specific antigen found in Giardia cysts.
High sensitivity (97%) and specificity (100%).

Best for:

Symptomatic patients with repeated negative stool microscopy