Giardia

Giardia Dr. Mejbah Uddin Ahmed

Flagellates  Flagellates  These

are equipped with flagella.

are known to inhabit: reproductive tract, alimentary canal, tissues blood stream, lymph vessels and cerebrospinal fluid.

Classification of flaellates: Flagellates inhabit the intestinal tract: Giardia lamblia- Pathogenic Dentamoeba fragilis- Nonpathogenic Chilomastix mesnili – Nonpathogenic T. hominis – Nonpathogenic T. tinax – Nonpathogenic

Flagellates inhabit the urogenital tract: Trichomonas vaginalis. Blood and tissue flagellates: Trypanosoma cruzi Trypanosoma brucei Leishmaina donovani L. brasiliense L. tropica

Giardia

 The

parasite Giardia duodenalis also

known as G. lamblia or G. intestinalis was the first parasitic protozoan of humans seen by Antonie van Leeuwenhoek in 1681.

Risk factors:  Children  Child

attend day care centers.

care workers, parents of infected

children  Who

drink unfiltered, untreated water

 Swimmers

while swimming in lakes, rivers,

ponds, and streams.

 Taxonomy:

Phylum- Metamonida, Class- Trepomonida, Order- Giardia, Genus- Giardia, Species- Giardia intestinalis.

 Morphology:

Trophozoite & Cyst

 Trophozoite:  is

the active, motile feeding stage

 causes

pathology in small intestine.

 approximately

12 - 15 um long and 5 - 9 um

wide.  pear-shaped

with a cytoskeleton, two nuclei and four pairs of flagella.

 Cyst:  are

hardy and can survive several months in

cold water and resistant to chlorine.  are

oval size 5 - 10 um in diameter.

 contains  are

four nuclei.

non motile and no longer adheres to the

mucosal surface.

 Life

cycle at a glance:

 Stages:

Cyst & Trophozoite

 Infective

form: Cyst

 Pathogenic  Route

form: Trophozoite

of infection: Fecal oral route

 Diagnostic

form: Cyst & Trophozoite

Steps of life cycle: Ingestion of cysts with contaminated water & food ↓ In the small intestine, trophozoites releases ↓ Multiply by longitudinal binary fission ↓ Encystation occurs as the parasites transit toward the colon. ↓ Cyst & trophozoites passed in stool

 Pathogenesis:

There are several theories that

include: 

Direct damage



Apoptosis



Disruption of tight junction



Mechanical



Direct damage: Trophozoite causes direct damage to the intestinal brush border and mucosa.



Apoptosis: In the small intestinal epithelial cells.

Pathogenesis:  Disruption

of tight junction: This appears

to be that Trophozoites disrupt the tight junctional zona-occludens and increases permeability.  Mechanical:

Trophozoites interfere with the

fat absorption resulting in steatorrhea.

Clinical Features:  Acute

giardiasis: stetorrhea, abdominal

pain, bloating, nausea, and vomiting.  Chronic

giardiasis: recurrent malabsorption

may lead to malabsorption syndrome and severe weight loss.

 Laboratory

Diagnosis:

 Principle:

Giardiasis can be diagnosed by detection of cyst or trophozoite in feces, duodenal fluid or duodenal biopsy.

 Alternate

methods:

 Detection

of parasites by immunofluorescence

 Antigen  Direct

detection by: EIA, RIA.

fluorescent antibody (DFA) assay

 Detection

of nucleic acid by PCR

String test: The organism can be detected from duodenal content by string test.

Gelatin Capsule in Stomach