Giardia lamblia | Parasitology

The protozoon was initially named Cercomonas intestinales by Lambla in 1859. and renamed Giardia lamblia by Stiles.

Geographical Distribution: It is worldwide in distribution and is the most protozoan isolated from human stools

Habitat - It is a protozoan parasite that colonizes the upper portions of the small intestine, Giardia no- invasive and quite often results in asymptomatic infections. Morphology Giardia exists in two forms

Forms of giardia lamblia

1. Trophozoite   

2. Cyst

 Morphology Giardia exists trophozoite, Cyst  forms T

 

 

Trophozoites

• Giardia trophozoite exhibits a Characteristic pear Shape or that of a tennis badminton racket.
• It has a rounded anterior and pointed posterior end.  
• It is 12-15 Um wide and 2-4 um thick.
• The dorsal surface is Convex and for ventral Surface is Concave with a Sucking disc.
• There are two axostyles, two nuclei, and four pairs of flagella
• The nuclei are rounded midline placed one on each side of the midline
•  Each nucleus possesses a large central Karysome.
• There is a lack of chromatin which gives the nuclei a halo appearance.
• The median bodies are a pair of curved red- Shaped structures. Which lies posterior to nuclei
• These are involved with adhesive disc and its formation.
• The trophozoite exhibits distinctive erratic twisting motion
• It absorbs nutrients from the intestinal lumen via Pinocytosis.
• The trophozoite stage is also lumen via characterized by an asexual replication.
• Bath nuclei divide at about the same time and cytokinesis restores the binucleated State.

 

Cyst

• As an alternative to replication, the trophozoite can encyst.
• during encystment, the parasite rounds up, detaches from the intestinal epithelium, and Secreter a cyst wall.
• After cyst wall formation the parasite undergoes one round & nuclear without cytokinesis resulting in the division in four nuclei.
• The cyst is oval-shaped and typically. measure 11-14μm in length and 6-10 um wide.

 

Life cycle of giardia lamblia

• Giardia completes its life cycle in a Single host e.g. man
• 2 Cyst are the infective stage of the parasite.
• Infection occurs by ingestion of cysts in contaminated water, food by the fecal-oral route.
• From each cyst, two trophozoites are released.
• Trophozoites multiply by longitudinal binary fission remaining in the lumen of the proximal part of the duodenum or upper part of the jejunum.

Giardia lamblia life cycle

 

Pathogenicity 

• The pathological condition caused by Giardia is known  As giardiasis.
•  The incubation period is of 1-8 weeks.
• This interferes with the absorption of nutrients, especially fats
• When a parasite localizes in the biliary tract, it -may have chronic cholecystitis and jaundice

 

Clinical diagnosis and Symptoms

• The first signs of acute giardiasis include nausea, apathy. headache, loss of appetite, and an upper gastrointestinal uneasiness.
• Children exhibit Clinical symptoms more frequently than adults.
• Acute infections can also develop into long-standing subacute
• Severe Giardia lamblia infection can result in partial villi lactase deficiency is seen and may persist.

Laboratory diagnoses 

Microscopic examination of Stool - demonstration of Giardia trophozoite. and cyst in freshly passed the stood by warped preparation (Saline. and iodine) is useful for diagnoses...

 

Laboratory diagnoses  of Giardia lamblia