Parasitology practice 2/Health Sciences

College of Health Sciences
Dep. of Medical Laboratories
Parasitology Practice
3rd stage
Lecture 2
Dr.: Shameeran S. Ismael
BVM & S, M.Sc Medical Microbiology(Parasitology),
PhD Molecular Parasitology
Shameeran S. Ismael Parasitolog
Practice.Medical Laboratories, 2020

I. Stool examination

Examination of the Stool sample:
 There are two types of methods used for detection of
parasities in stool samples:
A. Qualitative Methods:
I. Macroscopic examination (consistency, composition and
color)
II. Microscopic examination:
1. Direct fecal smear
2. Concentration methods:
a. Floatation technique
b. Sedimentation techniques
c. Telmann Method
d. Baerman Method.
e. Adhesive Tape Method

B. Quantitative Methods:
To count the No. of eggs or larvae of parasites in
one gram of stool. There are two methods:
1.MacMaster Method
2. Stoll Method

I.Macroscopic Examination:
•Before any dilution, the entire sample should be examine
by eye to know normal consistency (solid, semi soil or
liquid), color, odor and composition (fecal material, mucous,
blood, pieces of tissues and undigested food); as the same
time examined macroscopically for the presence of adult
nematodes or segments of tapeworms.
A. Qualitative stool methods

• Solid specimens - cysts of protozoa and eggs/larvae
of helminths may be present.
• Semi-solid specimens (soft specimens) - all stages
may be present
• Liquid specimens - trophozoite stages are more
likely to be present.
Consistency of stool

Color of stool
• Dark Grey: due to excessive cocoa or chocolate
ingestion
• Reddish or blackish brown color: due to large
amount of fruits
• Green color: due to ingestion of green leafy
vegetables, administration of calomel due to
biliverdin
• Red color: due to Beat ingestion fresh blood
• Yellow color: due to rhubarb or senna ingestion,

• Clay color: due to obstructive jaundice,
barium meal x-ray
• Tarry black color: due to haemorrhage in
stomach/upper intestine •
• Dark brown to bright red: due to bleeding in
rectum or sigmoid colon
• Red streaks of blood on the surface of
feces: due to haemorrhoids, fissures,
carcinoma ,ulcerative colitis

Odour
• Normal odour is aromatic due to indole and
skatole
• Increased- excessive protein ingestion
• Sour rancid- fatty acid in milk indigestion (in
children and adults), normal in infants
• Putrid- severe diarrhea of malignancy,
gangrenous dysentery

Composition of stool
1.Mucus:
• Small amount of mucin is normal
• Small quantity: feces from small gut
• Excessive quantity: infection of intestine
• Entirely mucus with little or no feces and
streaks of blood: dysentery, ileo colitis,
intussusception

2.Blood:
• Absent in normal feces
• Formed stool with streaks of blood: lesion in
sigmoid colon, rectum or anal canal
• Liquid stool with bright red blood, pus and
mucus- bacillary dysentery, ulcerative colitis
• Semi formed stool with deep tarry black
blood: melena
• Loose stool with deep cherry red blood:
melena

3.Pus:
• Normally absent
• Pus with blooded mucus: ulcerative colitis,
bacillary dysentery, ulcerative carcinoma
4. Undigested food or fibers of some foods may
found in normal cases in stool
5. Segment of worms or entire worm may b
found in stool ex: Ascaris lumbricodies,
Enterobius vermicularis

 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

Purpose or advantages:
 Detect the light infection
 Reduce background fecal debris
 Increase relative number of parasites
 Preserve morphology of parasites
Disadvantages:
 Destroys trophozoite stages.

Thanks for attention,,,

Parasitology practice 2/Health Sciences

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