PARASITOLOGY
MSc. HALAH DAWOOD
Second stage – LAB. 2
A-Intestinal Protozoal Infections:
3- Giardiasis….Etiology: Giardia lamblia (Intestinal Flagellates)
Giardia lamblia, a flagellate, is the only common pathogenic protozoan found in the
duodenum and jejunum of humans. It is the cause of giardiasis.
Giardia duodenalis is another name commonly ascribed to the parasite that causes human
giardiasis; the term Giardia intestinalis is frequently used in Europe and Lamblia intestinalis
in the former USSR. Giardia is the most frequent cause of non-bacterial diarrhea in North
America and in most other places around the World and it recognized as one of the most
common causes of waterborne illness.
Morphology & Identification
Typical Organisms
Trophozoite of G. lamblia is a heart-shaped, symmetric organism 10–20 µm in length .
There are four pairs of flagella, two nuclei with prominent central karyosomes, and two
axostyles (rod-like supporting organelles). A large concave sucking disk in the anterior
portion occupies much of the ventral surface. The swaying or dancing motion of Giardia
trophozoites in fresh preparations is unmistakable. As the parasites pass into the colon, they
typically encyst.
Cysts are found in the stool—often in enormous numbers. They are 8–14 µm in length,
thick-walled, highly resistant [Note: G. lamblia cysts are resistant to chlorine concentrations
used in most water treatment facilities.], drug-resistant. There are two Culture Cultivation
for G.lamblia, though possible, is not diagnostically useful.
Pathogenesis & Clinical Findings
Giardia infections are often clinically mild, although in some individuals, massive infection
may inflame and damage the duodenal mucosa. The stools may be watery, semisolid, greasy,
bulky, and foul-smelling at various times during the course of the infection. Symptoms may
continue for long periods.
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