Giardia Lamblia

Anton Von Leeuwenhoek (1681) discovered Giardia Lamblia originally named Cercomonas intestinalis, later also known as Giardia intestinalis or Giardia duodenale in his stools, making it one of the earliest known protozoan parasites. It is called Giardia after Paris Professor Giard and Lamblia after Prague Professor Lambl, who provided a detailed description of the parasite. It is the most widespread intestinal protozoan pathogen found in the world. Infections may be asymptomatic or cause diarrhea.

Geographical Distribution

It is the most common and distributed protozoan pathogen. Geographies with less sanitation, especially tropics and subtropics, endemicity has been stable. Giardiasis-caused diarrhea by contaminated water often develops visitors to such locations. Urbanites are more common in children than in adults in a warm environment.


Giardia lamblia is the only protozoan species found in human small intestines lumens and resides in the duodenum and upper jejunum.


Exists in Trophozoite(Vegetative form) and cystic form.

Trophozoite and Cyst of Giardia lamblia


The vegetative type or Trophozoite is rounded anteriorly and pointed at a range of about 15 μm, 9 μm and 4 μm. It has been defined as pyriform, core or racket-shaped in various ways. It’s dorsally convex and has a concave swallowing disk that covers almost the whole of the anterior bone. It has 2 nuclei on both sides of the middle line, 2 axostyles along the mid-axis, four pairs of flagellas and 2 saucers produced by the parabasal or median species lying on the back of the sucking sheet.

It is necessary to note that the right name of the median bodies is misunderstood. Some texts refer to these systems as parabasal bodies rather than middle bodies, which means that they vary in both systems. Other texts treat median bodies as two terms of the same form and parabasal bodies. Its exact function is ambiguous.

The anterior end has a pair of flagella, while the posterior end has a pair. The remaining two flagella pairs are arranged laterally, extending from the axonemes to the body’s middle. Giardia lamblia Trophozoite has an extractor layer. The sucking disk, which covers 50 to 75 percent of the ventral surface, is the nutritional entry point for the infected human.


Cyst of Giardia lamblia microscopic image x40 wet preparation
Giardia Lamblia cyst on wet smear preparation, microscopic image x40

It’s the parasite’s  contagious stage. The cyst sized 12 μm x 8 μm is small and oval and enclosed by a hyalin cyst surface. Its internal arrangement contains two pairs of nuclei clustered together at one end. A young cyst contains 1 kernel set. The axostyle sits diagonally in the cyst surface , creating a dividing line. Remains of the flagella can be seen of the young cyst and of the sucking plate. Sometimes, the cytoplasm is drawn off the cyst surface , forming a clearing area. This is particularly true after formalin has been retained. Two nuclear and two median bodies comprise the immature cyst. The completely mature cysts comprise four nuclei that can be detected in the iodine-wet preparations and on permanent stains, and four median heads.

Life Cycle

Giardia completes  one of its life stage in host.

Infective form: Mature cyst.

Giardia Lifecycle

Mode of transmission: Intake of cysts in polluted water and food induces infection. In children, male homosexuals and mentally unstable individuals, direct person-to – person communication may also occur. Strengthened giardiasis susceptibility is linked with blood group A, achlorohydria, cannabis consumption, persistent pancreatitis, obesity and immune deficiencies such as the 19A deficiency, hypogammaglobulinemia. Within an hour of intake, the cyst becomes two trophozoites, which are subsequently multiplied by binary fission and colonized in the duodenum. The trophozoites reside in the two upper and the duodenes and feed pinocytosis. Encystment typically takes place in colon in unfavorable circumstance. Cysts pass by feces and stay active for many weeks in soil and liquids. In  a gram of stool there may be 200,000 cysts deposited. 10–100 cysts in the contagiouas dosage.

Laboratory Diagnosis

Trophozoite and cyst phases are found in stool specimen. The stool normally is rough, heavy, yellow, oily, diarrheal, and blood is not in the stool. Several specimens obtained at varying periods ought to be studied as trophozoites and cysts are irregularly excreted. The cyst of intestinal flagellates can easily be distinguished from G.lamblia because they are smaller and do not have the same distinctive aspect as G. Lamblia (do not have flagella remains).

Entererotest is a beneficial tool for collecting duodenal specimens. The patient swallows a coiled thread inside a tiny weighted gelatine capsule after the free end of the thread is connected to the test. The capsule travels to the duodenum through the stomach. The thread is extracted after 2 hours, inserted into saline, and manually shaken. The saline centrifuged layer is tested for Giardia. The usage of enterotest is not advised due to the test’s incredibly high expense.

There are some other screening methods used to detect G.lamblia including enzyme immunoassay ( EIA) and enzyme-linked immunosorbent assay (ELISA) identification of fecal antigens. In recent tests, direct fluorescence detection of both Cryptosporidium and Giardia Western immunoblotting (blot) study provided positive results.

Molecular techiniques using polymerase chain reaction (PCR) have also been used to demonstrate parasitic genome in the stool specimen.

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