Giardia lamblia

# Overview
Giardia lamblia (synonymous with Lamblia intestinalis and Giardia duodenalis) is a flagellated protozoan parasite that is responsible for the development of giardiasis.

# Higher Order Classification
Eukaryota, Diplomonadida group, Diplomonadida, Hexamitidae, Giardiinae, Giardia, G. lamblia

# Natural Reservoir
- Giardia affects humans and animals, such as cats, dogs, cows, beavers, deer, and sheep.

# Microbiological Characteristicsc
- Giardia lamblia is a flagellated, microaerophilic parasite.
- The trophozoite form of G. lamblia is pear-shaped and has a unique morphology that includes two identical nuclei, a ventral disc for adhesion to the host intestine, and flagella.

# Genome
- G. lamblia genome consists of 1.2 million base pairs (average GC content: 46%).
- The genome pairs are distributed across five linear chromosomes.
- Similar to other eukaryotes, each chromosome is flanked by the telomere sequence (5TAGGG3).

# Life cycle
Giardia belongs among the diplomonads.

## Non-infective Cyst
- The life cycle begins with a noninfective cyst being excreted with faeces of an infected individual. Once out in the environment, the cyst becomes infective.
- A distinguishing characteristic of the cyst is 4 nuclei and a retracted cytoplasm.

## Trophozoite
- Once ingested by a host, the trophozoite emerges to an active state of feeding and motility.
- After the feeding stage, the trophozoite undergoes asexual replication through longitudinal binary fission.
- 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.
- Distinguishing features of the trophozoites are large karyosomes and lack of peripheral chromatin, giving the two nuclei a halo appearance.
- SEM depicts the dorsal surface of a Giardia protozoan, isolated from a rats intestine. From Public Health Image Library (PHIL). 
- SEM depicts the mucosal surface of the small intestine of a gerbil infested with Giardia sp. protozoa.  From Public Health Image Library (PHIL). 
- SEM depicts a Giardia lamblia protozoan in a late stage of cell division that was about to become two separate organisms, producing a heart-shaped form.  From Public Health Image Library (PHIL). 
- SEM depicts the ventral surface of a Giardia muris trophozoite. From Public Health Image Library (PHIL). 
- SEM depicts dorsal surface of a Giardia protozoan, isolated from a rats intestine. From Public Health Image Library (PHIL). 
- SEM depicts some of the ultrastructural morphologic details of an oblong-shaped Giardia sp. protozoan cyst.  From Public Health Image Library (PHIL). 
- SEM depicts the ventral surface of a Giardia muris trophozoite that had settled atop the mucosal surface of a rats intestine. From Public Health Image Library (PHIL). 
- SEM depicts a Giardia lamblia protozoan that was about to become two separate organisms, as it was caught in a late stage of cell division. From Public Health Image Library (PHIL). 
- SEM depicts a Giardia muris protozoan adhering itself to the microvillous border of an intestinal epithelial cell. From Public Health Image Library (PHIL). 
- This photomicrograph depicts Giardia lamblia parasites using indirect immunofluorescence test for giardiasis. From Public Health Image Library (PHIL). 

# Differential diagnosis
Giardia lamblia infection must be differentiated from other causes of viral, bacterial, and parasitic gastroentritis.
8Small bowel diarrhea: watery, voluminous with less than 5 WBC/high power field
Large bowel diarrhea: Mucousy and/or bloody with less volume and more than 10 WBC/high power field
 It could be as high as 1000 based on patient's immunity system.
The table below summarizes the findings that differentiate inflammatory causes of chronic diarrhea