INTESTINAL PARASITES (Protozoa)
ZOOMASTIGOPHOREA Order: Diplomonadidae

GIARDIA INTESTINALIS 

gia1-ic

G.intestinalis trophozoite: life cycle.

gia2-ic

G.intestinalis trophozoite: G.intestinalis is a flagellated enteric protozoon 
that infects humans
and other large mammalians; it causes diarrhea and malabsorption.
Trophozoites live upon the surface of the villi of the small intestine.

gia3-ic

G.intestinalis trophozoite: the vegetative stage is 9-20 x 7-12 µm
and possesses 6 flagella; it has a convex dorsal surface and a flat ventral
surface with a disk-like depression, the sucking disk, used to attach to
the columnar cells of the intestine.

gia4-ic

G.intestinalis trophozoite: the free living organism has two nuclei
with a large karyosome.
The adhesive disk and the 4 posteriorly directed flagella are visible.

gia5-ic	giaLeo-ic

G.intestinalis trophozoite: using the trichrome stain the nuclei
and the flagella are clearly visible.
Trophozoites obtained by duodenal aspiration, trichrome stain.

gia5b-ic

Giardia cysts stained with Trichrome stain

gia6-ic

Gia_L-ic Giardia intestinalis Lugol 400X

G.intestinalis cyst: diagnosis of giardiasis is posed by observation of cysts
and/or trophozoites in faeces or duodenal aspirates.
Multiple examinations are often required to diagnose the infection
because of the irregular shedding of parasites.

gia7-ic

G.intestinalis cyst: cysts are oval, 8-14 x 5-10 µm, with four nuclei
and fibrils and flagella longitudinally oriented.
Diagnosis is possible also by detection of Giardia antigens in faeces with an EIA test.

gia7b-ic

G.intestinalis : trophozoites live upon the surface of the villi of the small intestine. 
A trophozoite attached to the columnar cells of the intestine. T.E.M.

gia8-ic

Giardia intestinalis: 4 ellipsoid cysts 8-12 X 7-10 µm in size. 
Stained fecal film. Wheatley modification of Gomori‘s trichrome technique. 
Objective 100 X 

gia9-ic

Giardia intestinalis: 1 cyst containing 4 nuclei, rest of flagella and sucking disc. 
Stained fecal film. Wheatley modification of Gomori‘s trichrome technique. 
Objective 100 X 

gia10-ic

Giardia intestinalis: trophozoites from diarrhoeal stools. 
Usually 12 X 8.5 µm in size. Stained fecal film. 
Wheatley modification of Gomori‘s trichrome technique. 
Objective 100 X

gia11-ic

Legend of the figure:
G. intestinalis trophozoites in a jejunal section.
Several sickle-like profiles are seen over the epithelium (H&E X400).
Autopsy of a 6-years-old undernourished boy.

Giardia 01-50x	Giardia 03-100x	Giardia 04-250x	Giardia 05-400x
Giardia 06-400x	Giardia 07-1000x	Giardia 08-1000x	Giardia 09-1000x

Giardia intestinalis: Small bowel sections showing giardia infection
with very mild architectural damage;
lymphoplasmocytic inflammation is mild as well.
H-E at different magnification 50 X to 1.000 X with oil immersion.

Case history

A 58 y caucasian woman underwent gastroscopy for suspicion of gastric cancer (histologically confirmed in antral and corporal biopsies).
In addition, multiple small (2 mm) duodenal polypoid lesions were biopsied;
normal villi, mild stromal inflammation, large reactive lymphoid follicles,
intraluminal mucin droplets, inflammatory cells and cellular debris,
were found at 50-100-250x; a higher magnification (400x and 1000x oil immersion) evidenced a number of crescent shaped basophilic organisms
(longitudinal sections) with a typical symmetry in transverse sections ;
pear shaped, binucleated organisms
(slightly less basophilic than the crescent-like counterpart)
were also apparent (frontal view).
In daily practice, absence of clinical suspicion, very mild inflammation,
low magnifications and hematoxylin-eosin stain, may mislead pathologists
and the diagnosis of Giardiasis could be omitted;
hence parasites maybe misinterpreted as mucus droplets,
nuclear debris and inflammatory cells
(very common features in routinary biopsies).

Gia12-ic	Gia08	Gia07
Gia06	Gia02	Gia01
G11	G6	400-01