LAB 5
Flotation
 The flotation procedure permits the separation of
protozoan cysts and certain eggs from excess debris
through the use of a liquid with a high specific gravity.
 The parasitic elements are recovered in the surface
film, and the debris remains in the bottom of the tube.
 This technique yields a cleaner preparation than the
sedimentation procedure.
Zinc Sulphate technique
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 Zinc sulphate centrifugal flotation technique is useful for the
recovery of protozoan cysts and helminthes eggs.
 Large trematode eggs, some tape worm eggs, and infertile
Ascaris lumbricoides eggs are not concentrated by this
method.
 Why can’t all helminth eggs be recovered using the
flotation concentration rather than the sedimentation
concentration?
 Some helminth eggs are quite heavy (unfertilized Ascaris
eggs) and will not float, even using zinc sulfate with a
specific gravity of 1.20. Other helminth eggs are operculated;
when the egg is placed in a high specific gravity solution, the
operculum “pops” open and the egg fills with fluid and sinks
to the bottom of the tube. Thus, both the surface film and
the sediment should be examined before reporting the
specimen as negative.
Materials and Method
 Zinc sulphate solution with specific gravity 1.18.
 Mix 330gm dry zinc sulphate in 670ml distilled water.
 Use the hydrometer or densitometer to adjust specific gravity
around 1.18
Notes :
Warning! May cause skin irritation. May cause eye irritation and
possible burns.
Evaporation Rate:< ether
Chemical Stability: Stable under normal temperatures and
pressures.
Zinc Sulphate centrifugal
flotation technique
Transfer about 0.5 teaspoon of stool to a test tube
containing 1-2 ml of water and comminute thoroughly
then fill the tube to within 2-3 mm of the top with water.
2. Centrifuge at 1500 rpm for 1 mint. Discard supernatant
fluid.
1.
If the sample contains a large amount of material that floats in water, you
may want to wash the sample before doing the flotation.
Add 1-3 ml of zinc sulphate solution to the sediment and
resuspend the sediment.
4. Fill the tube within 2-3 mm of rim with additional zinc
sulfate solution.
3.
5. Strain the suspension through strainer into paper
cup.
6. Return the suspension to the tube, and add enough
zinc sulfate solution to fill within 2-3mm of rim .
7. Centrifuge at 1500 rpm for a 1 minute. Allow the
centrifuge to come to a stop without interference or
vibration.
8. Without removing the centrifuge tube from the
centrifuge and using wire loop ,remove 1-2 drops
from the center of the surface film and add them to
the drop of iodine or water on the slide then make
examination .
Notes
 The surface film must be examined within a few
minutes after flotation is complete. Otherwise the
cysts and eggs may distort or collapse.
 If zinc sulfate is the only concentration method
used, both the surface film and the sediment should
be examined should be examined to ensure the
detection of all possible organisms.
 Why is the flotation concentration used less
frequently than the sedimentation
concentration?
 There are several reasons. First, not all parasites
will float; therefore, you need to examine both
the surface film and the sediment before
indicating the concentration examination is
negative. Second, the organisms must not be
left in contact with the high specific gravity zinc
sulfate for too long or protozoa will tend to become
distorted, so the timing of the examination is more
critical. Also, the specific gravity of the fluid will
need to be checked periodically.
Dog Tape worm
– Echinococcus granulosus
Fish Tape worm
– Diphylobothrium latum
Beef Tape worm
– Taenia saginata
Pork Tape worm
– Taenia solium
Dwarf Tape worm
– Hymenolepis nana
Tissue Cestodes
Ecchinococcus granulosus
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Ecchinococcus granulosus also known as hydatid worm.
Disease: Ecchinococcus (serious disease).
Adult lives in intestine of dogs but never in human intestine.
Definitive host: Dogs.
Dead end host: Human.
Intermediate host: sheep, cattle, horse, pigs.
Infective stage: ova by fecal oral route.
Diagnosis:
 Tests involve antigen antibody reaction.
 X-RAY examination.
Ecchinococcus granulosus stages
Intestinal Cestodes
Diphyllobotherium latum
• knows as abroad fish tapeworm which can cause Diphylobotheriasis.
• Mode of infection: through consumption of raw or undercooked fish
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contain plerocercoid larva.
Immature eggs are passed in feces of the mammal host (the definitive host).
After ingestion by a suitable freshwater crustacean (intermediate host), the
coracidia develop into procercoid larvae.
Following ingestion of the crustacean by a suitable second intermediate
host, the procercoid larvae are released from the crustacean and migrate into
the fish's flesh where they develop into a plerocercoid larvae
The plerocercoid larvae are the infective stage for the definitive host
(including humans).
Diagnosis:
– Stool analysis to finding typical eggs ( oval, yellow brown with
operculum at one end) and segments.
Diphyllobotherium latum eggs
 Of the 32 recognized species of Taenia, only Taenia
solium and Taenia saginata are medically important.
 Taenia saginata, which is also known as the "beef
tapeworm", though it also infects humans.
 Taenia solium, which is known as the "pork tapeworm".
Like Taenia saginata humans serve as its primary host.
 Both have mature, immature and gravid segments.
 Both have scolex provided with four cup- shaped
suckers, but T. saginata has an unarmed scolex while T.
solium has an armed scolex
• In both species the infective stage is the cysticercus.
• Cows are the intermediate host of T. saginata while pigs are
the intermediate host of T. solium.
• Definitive host: Human.
• Diagnosis:
– By finding gravid proglotid or eggs in stool.
• Eggs present in stool less often are proglottids.
– Direct fecal smear.
– Brine flotation technique.
• Taenia saginata and Taenia solium must be differentiated
from each other by the following:
 Mature segment, gravid proglotid and adult worm.
Taenia Egg
Taenia scolex
Taenia saginata
Taenia solium
Taenia mature segment
Taenia saginata
2 ovary lobes
Taenia solium
3 ovary lobes
Taenia Gravid Proglotid
Taenia saginata
Taenia solium
Taenia Adult worm
Taenia saginata
Taenia solium
Aspect
Taenia saginata
Taenia solium
Intermediate host
Cows
(Beef tape worm)
Pigs
(Pork tape worm)
Adult size
Longer ( 4 – 8 meters )
Smaller ( 2 - 4 meters )
Number of
segment
1000 – 2000
700 - 1000
Mature segment
2 lobes ovary
3 lobes ovary
Gravid proglotid
With 15 – 30 uterine branches
With 7 – 13 uterine branches
Scolex
Devoid rostellum and hooks
With rostellum and 2 rows of hooks
Larvae
Cysticercus bovis in cattle only
Cysticercus cellulosae in pig as well
as in man
Taeniasis
Taeniasis and cysticercosis
Comparison
Disease caused in
man
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Hymenolepis nana
 This is one of the most common cestodes of humans, especially
children. And it’s the smallest tape worm in man, also called
dwarf tape worm.
 Eggs measures 30-37u, and have double membrane and contain
six hooked oncosphere.
 The scolex of H. nana has four suckers and a short rostellum
with hooks.
 Infective stage: Eggs.
 Diagnosis:
 Stool examination to detect the eggs.
H. nana egg
Hymenolepis nana – The Dwarf
Tapeworm
Hymenolepis nana
(Dwarf Tape Worm)
Definitive host
Man
Intermediate host
No
Infective form
Eggs
Internal autoinfection
Mode of transmission
Ingestion
Site of localization
Small intestine
30
Hymenolepis nana scolex
Mature proglottid
Gravid proglottid