The microscopic examination of feces is required for the
recognition and identification of intestinal parasites:
1. Direct Microscopy:
• Advantages
Useful for the observation of motile protozoan
trophozoites.
• Disadvantages
May not detect ova, cysts and larvae which are present
in scant numbers.
Raed Z. Ahmed, Medical Parasitology Lab.,2012
2. Concentration techniques :
• Advantages
 Maximizes the numbers of organisms detected which
may be too scanty to be seen by direct microscopy
alone.
 Worm eggs, larvae, and protozoan cysts may be
recovered.
• Disadvantages
 Destroys trophozoite stages. Most concentration
methods destroy trophozoites stages.
 The purpose of concentrating feces is to increase possibility
to finding ova, cyst, or larvae in samples that not be able to
seen by direct microscopy.
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Concentration Methods
1. Sedimentation method
 Modified Formal- Ether sedimentation technique
 Acid- Ether sedimentation technique
2. Flotation method
 Saturated Salt Solution technique
 Sheather’s Sugar Centrifugal Flotation technique
 Zinc Sulphate Centrifugal Flotation technique
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Materials and Method
 Libra
 Applicator stick
 Glass centrifugal tubes
 Beaker
 Wire sieve
 Vortex or whirlimixer
 Centrifuge.
 Reagent:
Reagent I: 10% formalin solution in distilled water.
Reagent II: diethyl ether or ethyl acetate.
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Procedures
1. Emulsify 1 gm. of feces in 7 ml of 10% formalin in a
centrifuge tube.
2. Strain the suspension through a brass wire sieve, and
collect in beaker.
3. Pour the filtrate into a 15 ml boiling tube and add 3 ml
of ether, then mix well 15 sec on vortex or whirlimixer
or 1 min by hand.
4. Transfer the ether- formalin suspension back into the
washed centrifuge tube, and centrifuge at 3,000 rpm for
1 min.
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Procedures (cont.)
5. Loosen the fatty layer and debris at the top of the tube
with an applicator stick and invert the tube quickly to
discard the supernatant.
6. On righting the tube, a few drops only should remain
with the sediment, mix the sediment well and transfer
one drops onto a glass slide and cover it with coverslip.
7. Scan the whole coverslip using 10x objective, turning
into 40x for confirmation of identification of parasites.
Modified Formal- Ether Sedimentation
• Formalin- Ether or Formalin- Ethyl acetate method is the recommended
concentration procedures.
• Most types of worm eggs (round worms, tapeworms, schistosomes, and
other fluke eggs), larvae, and protozoan cysts may be recovered by this
method.
• Advantages:
1. Speed: one sample can be processed in 5 minutes.
2. Broad spectrum: it will recover most ova, cyst and larvae.
3. The morphology of most parasites is retained for easy identification.
• Disadvantages:
1. Requires several pieces of apparatus which does not make it an easy.
2. The preparation contains some debris.
3. Ether is flammable. Formalin is an irritant.
4. Hymenolepis nana and Fasciola spp. do not concentrate well.
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Materials and Method
 Libra
 Applicator stick
 Glass centrifugal tubes
 Beaker
 Wire sieve
 Vortex or whirlimixer
 Centrifuge.
 Reagent:
Reagent I: 15% Hydrochloric acid.
•
Conc. HCl 40 ml + 60 ml Distilled water.
Reagent II: diethyl ether or ethyl acetate.
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Procedures
1. Mix thoroughly 1 gm. feces with 3 ml of 15% of
hydrochloric acid and then mix well.
2. Add and additional 5-6 ml of 15% HCl and mix.
3. Strain the suspension through a wire sieve into beaker.
4. Place suspension in a glass centrifuge tube and make up
to the 10 ml with distilled water.
5. Add 4 ml of ether, stopper the tube and shake
vigorously 20 -30 sec using vortex.
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Procedures (cont.)
6. Centrifuge 2-3 min at 1500 rpm, the suspension now
will be layered.
7. Loosen plug of debris with applicator stick and
immediately pour off liquid.
8. Transfer one drops onto a glass slide and cover it with
coverslip.
9. Scan the whole coverslip using 10x objective, turning
into 40x for confirmation of identification of parasites.
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Giardia lamblia
• It is the most common flagellate of the intestinal tract that
cause giardiasis, Traveler's diarrhea.
• There is two diagnostic stages for Giardia lamblia :
1. Cyst (infective stage).
2. Trophozoite (motile form, motility by flagella).
• Diagnosis:
– Stool examination to see cyst stage, or trophozoite
stage if the sample is fresh.
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Life cycle
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Giardia lamblia cyst
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Giardia lamblia Trophozoite
Raed Z. Ahmed, Medical Parasitology Lab.,2012