Download Giardia Lamblia

Giardia Lamblia
Artistic impression by Russel Kightley
Source: http://soils.cses.vt.edu
Giardia
 Giardia lamblia is a flagellated protozoan that
infects the duodenum and small intestine.
 range from asymptomatic colonization to acute
or chronic diarrhea and malabsorption.
 more prevalent in children
 Belongs to genus-Giardia-order-diplomonadida
 Synonym- Giardia intestinalis ,lamblia
intestinalis
HISTORY
First seen by Leeuwenhoek –(1681) 
while examining his own
stool
Alexeieff- 
1914
EPIDEMIOLOGY
 usually occurs sporadically
 major reservoir for spread :water contaminated
with Giardia cysts
 Giardia cysts are relatively resistant to
chlorination and to ultraviolet light irradiation
 Boiling is effective for inactivating cysts.
 Geographical distribution-world wide
 Human milk contains glycoconjugates and
secretory IgA antibodies that may provide
protection to nursing infants.

Transmission
-Water sports, surface contamination.
Watershed contamination

Habitat - 
-duodenum and upper part of jejunum 
of man
morphology
Exists in two phases-trophozoite and cyst form 
Trophozoite form-when viewed flat-appears like 
tennis or badminton racket-when viewed side –onresembles –spit pear
Size-14µm long 
Anterior end is broad and rounded-posterior end 
tapers
Is bilaterally symmetrical & all organs are paired

Tear drop shaped
2 adhesive discs,
2 median bodies,
2 nuclei
4 pairs of flagella
CYST–is fully formed cyst –oval in shape 
=12µm long 7µm broad
The axostyles lie –more or less diagonally- 
form sort of dividing
line
There are four nuclei –remain clustered at 
one end 
An acid environment-often cause parasite to 
encyst
four pairs flagellae
a flat ventral surface
sucking or adhesive disk
8 to 12 mm long and 7 to 10 mm wide
Source: http://soils.cses.vt.edu
convex dorsal surface
LIFE CYCLE
life cycle of G. lamblia is composed of
2 stages:
 trophozoites
 cysts
In tropozoite 
stage
Parasite multiplies(intestine of man –binary 
fission)
when

unfavourable condition in duodenum(encystment
occur
during encystment cells then divide into two within the
cyst
infection to man is brought by ingestion of
cyst
Source: Doug Allington
Trophozoites : Lives in duodenum, jejenum and upper ileum
They come in close contact to the mucosal, but do not invade
the host. Adhesive disc fits over surface of epithelial cell
The flagella act as a pump to move nutrients away from the
microvilla and hold the adhesive disc near the mucosa.
Rapid division to produce large numbers quickly
Pathogenesis and Immune response (1)
The production of diarrhea, and occasionally malabsorption, is •
the result of a complex interaction of Giardia with the host,
Infection occurs after oral ingestion of as few as 10 to 25 •
cysts.
After excystation, trophozoites colonize and multiply in the •
upper small bowel
Adherence of G. lamblia in the human gut may be via the disc •
but may also involve specific receptor-ligand interactions
Pathogenesis and Immune response (2)
Several pathogenic mechanisms have been postulated
Disruption of the brush border
Mucosal invasion
Elaboration of an enterotoxin
Stimulation of an inflammatory infiltration leading to fluid and
electrolyte secretion and occasionally to villous changes
Source: Gallery of histology Woods and Ellis2000
Ventral sucking disc
TEM micrograph showing the method of attachment to
the duodenal wall.
Immune Response
Partially protective immunity may develop to Giardia
Immune response involves both cellular and humoral immunity
Ig A, serum Ig G and Ig M are detected in patients: role of Ig A
is not completely understood, probably inhibits trophozoite
attachment
IgA deficiency lead to chronic giardiasis
Cell mediated immune response may also play a role
Human milk may also play a role in protection of the host against
Giardia : Free fatty acids and IgA antibodies
CLINICAL MANIFESTATIONS
 incubation period :1–2 wk
 clinical manifestations :asymptomatic . acute infectious
diarrhea, chronic diarrhea with failure to thrive and
abdominal pain or cramping.
 Symptomatic infections occur more frequently in
children than in adults.
 Most symptomatic patients : acute diarrhea. low-grade
fever, nausea, and anorexia;
 intermittent or more protracted course characterized by
diarrhea, abdominal distention and cramps, bloating,
malaise, flatulence, nausea, anorexia, and weight loss
develops
CLINICAL MANIFESTATIONS
 stools may be profuse and watery and later
become greasy and foul smelling
 Stools do not contain blood, mucus, or fecal
leukocytes
 Varying degrees of malabsorption may occur.
 Abnormal stool patterns may alternate with
periods of constipation and normal bowel
movements.
 Malabsorption of sugars, fats, and fatsoluble vitamins has been well documented
and may be responsible for substantial
weight loss.
 Giardiasis has been associated with growth
stunting and repeated Giardia infections
with a decrease in cognitive function in
children in endemic areas.
 Giardiasis should be considered in young children
in child care or in any person who has had contact
with an index case or a history of recent travel to
an endemic area who has persistent diarrhea,
intermittent diarrhea and constipation,
malabsorption, crampy abdominal pain and
bloating, failure to thrive, or weight loss
DIAGNOSIS
 established by microscopy documentation of
trophozoites or cysts in stool specimens,
 3 stool specimens are required to achieve a
sensitivity of >90%.
 Stool enzyme immunoassay (EIA) or direct
fluorescent antibody tests are more sensitive
 aspiration or biopsy of the duodenum or upper
jejunum -Enterotest
Enterotest
Uses a coiled thread inside small weighted gelatin 
capsule
Swallowed after attaching the free end of the thread to 
cheek
Capsule passes through stomach to duodenum 
After 2 hours, thread is withdrawn ,placed in saline 
Centrifuged deposit of saline is examined for giardia 
TREATMENT
 should receive therapy :
acute diarrhea
failure to thrive
exhibit malabsorption
Treatement
Metronidazole (250mg TID -5 days) 
Trimidazole(2gms OD)

Furozolidone(100mg QID)-7-10 -days 
PREVENTION
 Handwashing
 purify public water supplies adequately include
chlorination and filtration.
 Travelers to endemic areas are advised to avoid
uncooked foods that might have been grown,
washed, or prepared with water that was
potentially contaminated.
 Purification of drinking water can be achieved by a
filter or by brisk boiling of water for at least 1 min