Life Cycle of Giardia Intestinalis

Classifications Phylum: Protozoa Class: Flagellata Order: Diplomonadida Genus: Giardia Species: lamblia

GIARDIA INTESTINALIS

Giardia lamblia is a flagellated protozoan parasite that colonises and reproduces in the small intestine, causing giardiasis. The giardia parasite attaches to the epitheleum by a ventral adhesive disc, and reproduces through binary fission. Giardiasis does not spread through the bloodstream, nor does it spread to other parts of the gastro-intestinal tract, but remains confined to the lumen of the small intestine.

Host: Giardia infects humans, but is also one of the most common parasites infecting cats, dogs and birds. Mammalian hosts also include cows, deer and sheep.

History

1681 AD: Leeunwenhock found this parasite while examining his own stool

1859: Lambl describe it as the parasite for the first time and named as intestinalis

It was named as Giardia lamblia by the Prof. Giard and Prof. Lambl

Distribution:

Worldwide, more prevalent in warm climates, and in children. Since 1988, WHO has estimated that in Africa, Asia and Latin America there are over 280 million G. intestinalis infections yearly…..

Habit and Habitat: It is the most common intestinal protozoan parasite found in the duodenum and the upper part of jejunum of human small intestine.

Morphology

It exists on two stages namely, Trophozoite and Cystic stage

Trophozoite Stage:

Bilaterally Symmetrical

Paired Body Organs

Rounded Anteriorly and Pointed Posteriorly

Looks like longitudinally split pear or tennis racket

Dorsal surface is convex and the ventral concave

Size: 14 µm

Body Organells- Two axostyles, two nuclei, four pairs of flagella, 2 parabasal body and one sucking disc

They are found attached on the epithelial surface of small intestine by the help of sucking disc.

Cystic Stage

Ø Oval in shapes (12 µm long and 7 µm broad)

Ø Four nuclei are presents in cluster

Ø Retracted Cytoplasm

Ø The axostyle lie more or less diagonally seems like a dividing line within the cyst wall.

Ø Flagella are retracted and curved.

Life Cycle:

Giardia infection can occur through ingestion of dormant cysts in contaminated water, food, or by the faecal-oral route (through poor hygiene practices). The Giardia cyst can survive for weeks to months in cold water and therefore can be present in contaminated wells and water systems, especially stagnant water sources such as naturally occurring ponds, storm water storage systems, and even clean-looking mountain streams.

Within 3o minutes of ingestion, the cyst hatches out into trophozoites. The pear-shaped,

flagellated trophozoite inhabits the epithelial border of the upper two-thirds of the small

intestine, where it absorbs nutrients from the intestinal tract and reproduces by binary fission, approximately every five hours.

When the condition in the duodenum is unfavorable, encystment occurs and the cell divides into two within the cyst. The resulting trophozoites and cysts then pass through the digestive system in the feces. While the trophozoites may be found in the feces, only the cysts are capable of surviving outside of the host. Diarrheal stools may contain trophozoites due to rapid intestinal transit that may not allow sufficient time for cysts to form

Mode of Infection:

Mature Cyst is the infective stage. Infection is fecal-oral type. It is brought about by the ingestion of mature cysts through food or drink contaminated with cysts.

Pathogenicity

Ø With the help of the sucking disc, the parasite attaches on the epithelial cells of intestine and may cause disturbance in intestinal function

Ø Steatrrhoea (pale, foul smelling, greasy stools)

Ø Chronic enteritis and acute entero-colitis

Ø Allergy due to toxic effect of parasite

Ø Jaundice, loss of weight, appetite, weakness etc

Diagnosis

Ø Direct microscopic examination of stool specimens for cyst and trophozoites.

Ø Direct Fluorescent Antigen (DFA) test of stool specimens for cysts and trophozoites

Tratment

Metronidazole, Furazolidone (effective for children) and Chloroquine.

Prevention

Ø Washing hands with soap and water after toilet,

Ø Cutting nails regularly;

Ø Using boiled water;

Ø Consume properly washed vegetables,

Ø Protection of foods from possible contamination with flies and

Ø Proper disposal of sewages,