Parasitology practice Lecture 3/Health Science

College of Health Sciences
Dep. of Medical Laboratories
Parasitology Practice
3rd stage
Lecture 3
Dr.: Shameeran S. Ismael
BVM & S, M.Sc Medical Microbiology(Parasitology),
PhD Molecular Parasitology
Shameeran S. Ismael Parasitolog
Practice.Medical Laboratories, 2020

 Direct fecal smears can be used as a
quick screening test to check for any
intestinal parasite.
II. Microscopic examination of stool:
1.Direct fecal smears:

 Useful for detecting motile organisms.
 Protozoa are often detected via a direct fecal
smear.
Quick process.
Advantages:-

 Small size of the sample limits its usefulness.
 You may get inaccurate results.
 If your examination finds no evidence of a parasite
but the patient or animal actually harbors the
parasite, then the results are called a false negative
result. False negative results are common with
direct fecal smears.
Disadvantages:

1. Put small amount of feces on glass slide.
2. Mix with drop of saline or water.
3. Place cover slip on mixtures.
4. Examine under microscope.
If the feces is already in a liquid state because the
patient or animal has diarrhea, obviously no fluid is needed to
spread the feces over the slide.
Procedure:

feces+ saline on the
slide
Mix until it is
dispersed
Examine under
microscope

1. A wet mount, or can be
2. Dried and stained
Direct fecal smears may be examined as:

Microscopic examination of fecal material
Wet mount Stained smear

 The fecal smear may be examined in
its wet state by simply placing a
cover slip over the drop of wet fecal
material.
 This method is most useful looking
for trophozoites which can be
observed by their characteristic
movement and appearance.
1. Wet mount technique:

 A drop of stain can be added before the cover
slip is placed or after having examined the
unstained preparation.
 The stain will diffuse and then you can
examine it.
 The iodine will stain the organisms a dark
orange brown color.
 If you use new methylene blue instead, you will
see organisms contrasted against a blue
background.
WITHOUT STAINING
Staining:

Note:- You can choose to look at the unstained
preparation first for motile forms, and then add
stain by applying it at the edge of the coverslip.
Methylene blue stain at the edge
of the cover slip with a Pasteur
pipette.
Stain will diffuse
Application of
iodine stain

 The fecal smear may be examined in a dry state
and stained.
 Prepare the slide as for a wet mount, but instead
of placing a cover slip, let it dry so that only a
thin film is visible on the slide.
 It should be heat fixed by passing it over a
flame for a few seconds.
 Then you can stain it.
A thin fecal smear is
prepared and dried
2. Dry mount technique:

 The stains most commonly used are the acid fast stain.
 If you are trying to rule out Cryptosporidium spp., then
the acid fast stain is the stain of choice.
Staining:

Under microscope
Schistosoma spp egg
Protozoa appear
Iodine stain. an Entamoeba coli
trophozoite

 A concentration technique is performed
mainly to separate the parasites from fecal
debris.
 The concentration procedure not only
increases the number of parasites in the
sediment but it also unmasks them, making
them more visible by removing organic and
inorganic debris.
II. Concentration Methods

Advantages of concentration method:
 Detect the light infection
 Reduce background fecal debris
 Increase relative number of parasites
 Preserve morphology of parasites
Disadvantages:
 Destroys trophozoite stages.

1. Flotation Method:
• In tape water, worms eggs will sink because their
specific gravity is a little higher than 1. When
fecal samples are suspended in a liquid with
specific gravity higher than that of the eggs and
the water, the eggs will float up to the surface.
Concentration methods includes:

 Operculated eggs as well as schistosoma spp. and
Ascaris eggs are not easily recovered by this method.
 Also trophozoites are killed due to the high specific
gravity

1. Saturated sodium chloride (salt): Mixed 400g of salt
with 1L of hot distal water.
2. Sugar solution (Sheather’s sugar) : 1300 g/L of D.W
3. Saturated sodium Nitrate NaNO3: (400g/ L of
D.W)
4. Saturated Zinc Sulphate ZnSO4: (700g/ L of D.W)
5. Magnesium Sulphate MgSO4: (500g/L of D.W)
Common Flotation or Saturated solution

Advantages:-
 The concentrate is clear of debris
Disadvantages:-
 Delay in examination can result in distortion
 Larvae and some fluke eggs do not concentrate
Advantages and Disadvantages of flotation fecal
method:

1.Mix 3-5 g of fresh feces with little amount of
concentration solution.
2.Dilute then with concentration solution while stirring
vigorously to obtain a homogenous mixture.
3.Solution will be strained through a fine sieve and
residue will be pressed out.
4.Fills test tubes with this solution and carefully put
cover slide on the top of the tube.
Procedure:

5. After 10-30 minutes, the cover slide is gently removed
and put on slide, then examined under microscope.
6. This method is suitable for the majority of nematode
eggs, cestodes and protozoa.

7. Nematodes and cestodes eggs float in a liquid with
a specific gravity between 1.10-1.2 by using sodium
chloride or magnesium sulphate flotation solution.
Trematode eggs which are heavier require a specific
gravity of 1.30-1.35 by using zinc chloride or zinc
sulphate flotation solution.

Thanks for attention,,,

Parasitology practice Lecture 3/Health Science

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Parasitology practice Lecture 3/Health Science