Giardia Duodenalis (Lamblia)

Geographical Distribution
- Worldwide: More prevalent in the developing world
- More common in warm than in cool climate
- Man, especially children
- Mice and rats can be infected
Site of infection (Habitat)
- Small intestine especially duodemnum, jejunum and upper ileum
- Swim free, rapidly in spiral motion and attached to intestinal epithelium
- Bile duct and Gall bladder occasionally invaded
- Vegetative form (Trophozoite) --> 7-22microns. Average 14-15 microns
- Cyst form: 10-14 microns
How many pairs of flagella?
Describe the shape
Oval or pear shaped.
Broad anteriorly, tapering posteriorly.
Flat ventral surface, convex dorsal surface.
How many nuclei?
two nuclei, each with central karyosome
Where is the sucking disc?
The anterior portion of the ventral surface. It is bordered by the curved intracytoplasmic portion of the anterior flagella axonem.
What is the purpose of the sucking disk?
Attachment (mechanical irritation)
On which surface (ventral or dorsal) are the structures symmetrically represented?
Axonems of the caudal pair of flagella are
straight, closely approximated, run parallel to each other dividing the body into two halves through the whole length
How does it multiply?
By longitudinal binary fission
What environment favours multiplication?
An alkaline environment, increased by achlorohydra & rich carbohydrate diet
Where is the cyst commonly seen?
In stools
Ecystation starts ____ and proceeds _____.
Starts anteriorly, proceeds posteriorly
The trophozoite in the duodenum encysts by the time they reach the ____
What kind of stools can the trophozoites be seen in?
Diarrheic stool
Under moist conditions, cysts will ____
remain viable for months outside the host
Morphology of the cyst?
1. Oval & the contents are shrunken from cyst wall
2. Four nuclei
3. Axostyle, visible as 2 rods dividing cyst
4. Parabasal bodies cross axostyle
5. Remnants of flagellae, coiled
How is it transmitted?
- Through food and water contaminated with sewage flies or food handlers, and hand to mouth
- It is more common in population groups practising anal-oral intercourse
Pathogenesis: How many cysts are needed, and where does it occur?
- As few as 10 are able to produce infection
- Encystation occurs in the upper regions of the small intestine, where the parasites multiply by simple binary fission
Explain the mechanisms of mucosal injury
1. Attachment of trophozoite to the epithelium can disrupt and distort microvilli
2. Trophozoites produce cytopathic substances responsible for this disruption of epithelial structure and function (proteinases & surface lectin)
3. Mucosal damage occurs by both mechanical and biochemical factors
Explain histological features of the pathology
Shortening of the villi, cellular infiltration of the lamina propria of the mucous membrane
_____ infections are usually asymptomatic
How does it cause diarrhea?
Attachment to mucous membrane --> Inflammation & hyperaemia --> Diarrhea
How does it cause fatty stools and steatorrhea
Associated with inability to absorb fats and vitamin A (malabsorption)
How does it cause peptic ulcer?
Duodenitis and even duodenal ulcer with hunger pains may occur
If it reaches the gall bladder...
give a picture of cholecystitis
The parasite may induce motility disturbances and cause
Abdominal cramps
What is the microscopical observation?
Cysts are seen more than trophozoites.
- In diarrheic stools, it is usual to find only trophozoites
- Concentration technique such as zinc sulfate floatation is useful
- No RBCs or Charcot Leyden crystals
-Fat globules
Duodenal aspiration is more reliable if?
No cysts are passed (contents may be cultured)
Duodenal content may be sampled by the _____ which is gelatin capsule containing a coiled thred
Enterotest capsule
- Metronidazol (Flagyl)
- Tinidazol
- Treatment of cases
- Personal hygeine
- Fly control
- Proper sewage disposal
- Proper water supplies
- Chlorinating water does not kill the cyst, water should be boiled or filtered to remove the parasite