Giardia intestinalis

Systematic position Phylum- Protozoa

Subphylum-

Sarcomastigophora

Class- Mastigophora

Order- Polymastigina

Genus- Giardia

Species- intestinalis

First

Seen

by

Leeuwenhoek

in 1681

Discovered

in

his

own

stool

Worldwide

Duodenum

& upper

part

of

jejunum

(man)

2

phases:

Trophozoite

Cyst

Cyst

Trophozoite

Trophozoite

Looks-like

tennis

racket

(flat view)

A

split

pear

longitudinal

view

Dorsal surface:

Convex

Ventral surface:

Concave

A

sucking

disc

√

14 µm

long

&

7 µm

broad

Anterior

end

broad

&

rounded

Posterior

End

tapers

to a

sharp

point

Bilaterally

symmetrical

All

body

organs

paired

2

axostyles,

2

nuclei

4

pairs

of

flagella

Cyst

Oval,

12 µm long,

7µm broad

Axostyles

lie

more

or

less

diagonally

Form

a sort

of

dividing

line

4 nuclei,

clustered

at one

end/at

opposite

ends

Remains of

flagella &

margins of

sucking disc

(cytoplasm)

Acid

environment

causes

parasite:

Encyst

Trophozoite:

multiplies

(man’s

intestine)

by

binary fission

Unfavorable

conditions:

parasite

encysts

(large

intestine)

Cyst:

a thick

resistant

wall

secreted

by parasite,

Divides

into

2

within

cyst

Man

becomes

infected

(ingestion

of

cysts)

After

30 minutes

of ingestion

cyst hatches

into 2

trophozoites

Multiply in

enormous

numbers,

colonize in

duodenum

To avoid

high acidity

Giardia

localises

in

biliary tract

Sucking

disc

helps

in

attachment

Convex

surface

attaches

(epithelial

cells)

Causes

disturbance

in

intestinal

function

Leading to fat

mal-absorption

Patient

may

complain

looseness

of

bowels

Mild

steatorrhoea

(passage of

yellowish/

greasy

stools

Parasite

capable of

causing

harm:

toxic effects

(allergy)

Microscopical

examination:

freshly

passed

stool

Traumatic,

irritative

&

spoilative

action

Demonstration of

trophozoites/cysts

Trophozoites:

recovered

both

in bile

A & B

Bile A:

aspirated

from

duodenum)

Bile B:

removed

from

bile

duct

Atebrin

Acranil

Schneider

(1961)

√results:

imidazole

derivative

Chloroquine

doses

of

300 mg

base

Once

daily

for 5

days

is also

effective

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