Investigations

Diagnosis of Giardia Lambdia parasite

Diagnosis confirmed by presence of: 

- Cysts in patient’s stool

- Trophozoite in diarrhoeal stools, duodenal contents and jejunal biopsy.

Parasite Diagnosis:

- Cysts of G. intestinalis in the formed stool or the trophozoites by the parasite in the diarrhoeal stools,  duodenal contents and jejunal biopsy

Stool examination:

- Microscope examination of stool for trophozoites and cysts is a routine method.

- Stool specimens examined are either fresh or preserved in formalin solution.

- In acute giardiasis, wet mount preparation of:

o   Liquid stools – look for the presence of motile trophozoites.

o   Semi solid stools – Cysts are demonstrated.

- In chronic giardiasis

o   Cysts are excreted at certain time interval

*it requires examination of at least three-stool specimen for correct diagnosis.

Detection of Giardia Antigen:

Presence of Giardia antigen in the stool is detected using techniques of:

         -Counter Current Immuno-Electrophoresis (CIEP)
     -Enzyme Linked  Immunosorbent Assay (ELISA)

 Examination of Duodenal Contents:

Microscopic examination of duodenal contents is carried out when repeated stool examination is negative but giardiasis is still suspected.

The methods followed to collect the duodenal contents are:

   1.       String test/Entero test:

-   The nylon string consists of a gelatin capsule at one end. The patient swallows the capsule and the free end of the string is fixed in the mouth.

-   In the stomach, the capsule is dissolved and the string remains in the duodenum and jejunum. After overnight incubation, the string is removed and the bile stained mucus is collected on the glass slide and examined microscopically for trophozoites.

   2.       Duodenal aspiration:

-   Collected to demonstrate trophozoites

   3.       Jejunal biopsy:

-   Collected to demonstrate trophozoites but is indicated only in very serious cases.

   4.       Serological Diagnosis:

-   ELISA and Indirect Fluorescent antibody are useful in detection of Giardia antibodies in the serum, which remains elevated for longer period.

-   Axenically cultured G. intestinalis trophozoites are used as antigens in these assays.