Clinical Parasitology (Lecture)
Phylum Platyhelminthes
ADULT TAPEWORM PARTS
PHYLUM PLATYHELMINTHES
GENERAL CHARACTERISTICS
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Multi-celled animals
Leaf-like
Bilaterally symmetrical
Lack body cavity, circulatory and respiratory structures
Possess an incomplete digestive tract
Sexual organs are complicated
Life cycle consists of a single obligatory host
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Class Tubelaria
o Mostly free-living fresh water organisms.
o Body is dorsal ventrally flattened
Examples: Planaria, Bipalium, Otoplana, Notoplana
THREE IMPORTANT CLASSES
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Class Trematoda
o Mostly parasitic
o Body is dorsal ventrally flattened leaf-like
Examples: Fasciola hepatica (Liverfluke), Diplozoon
Class Cestoda
o Mostly parasitic
o Body is dorsal ventrally flattened tape-like
Examples: Taenia spp. (tapeworm), Convoluta,
Echinobothrium
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PROGLOTTIDS
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Parasitic organisms
Hermaphroditic (both sexes)
Covered with non-ciliated integument
Scolex are provided with suckers
No digestive tract in most species
Divided transversely into separate sexually complete units.
Craspedote – posterior border of proglottids overlaps the
anterior border of adjoining proglottid.
Acraspedote – posterior and anterior border of proglottids
do not overlap.
Apolytic – premature detachment of proglottids that follows
the release of eggs.
Anapolytic – proglottids are not shed from the strobila and
eggs are released in other ways.
EGGS
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Cyclophillidea (cestodes parasite) are released from the
uterus by apolysis.
Spherical, non-operculated and almost fully embryonated
when discharged from proglottids.
LARVAE OF TAPEWORMS
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CLASS CESTODA
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Has three parts mainly: scolex, neck, strobila
Length varies from 3mm to 10 meters or more and the
number of proglottids ranges from 3 to 4,000
Gravid proglottids are located in the distal portion of the
scolex wherein the primary genitalia have been atrophied
and consist essentially of a uterus distended with eggs.
Proglottids maybe described as craspedote, acraspedote,
apolytic and anapolytic.
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Solid type
Procercoid – This larva is relatively globular with the scolex
invaginated into the body of the larva.
Plerocercoid/sparganum larva – This larva is elongated
with head free or invaginated only to the neck.
TWO IMPORTANT ORDER OF CLASS CESTODA
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Order Pseudophillidea
o Scolex is unarmed
o Equip with a dorsal and ventral groove
o Scolex is spatulate
o All representatives in man belong to superfamily
Bothriocephaloidea
Order Cyclophillidea
o Scolex with 4 suckers and usually a centrally placed
apical rostellum
o Armed with hooks
o Scolex is quadrate
o Sex pores open laterally
o Species found in man belong to superfamily
Taeniodea.
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Cystic type
Cysticercoid – This larva is provided with a slightly
developed bladder anteriorly.
Cysticercus – head is invaginated into the proximal portion
of the bladder.
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TRANS:
MEDICALLY IMPORTANT SPECIES OF
TAPEWORMS
Pseudophillidea
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Diphyllobothrium latum
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Cyclophillidea
Taenia solium
Taenia saginata
Dipylidium caninum
Hymenolepis diminuta
Raillietina garrisoni
Hymenolepis nana
Echinococcus granulosus
Echinococcus multilocularis
Spirometra mansoni
TREATMENT
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Praziquantel
If not available, niclosamide
hydrochloride maybe used.
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Common name: Pork tapeworm
Disease
caused:
Pork
tapeworm
infection/taeniasis
Small intestine
2-4 meters with 800-1000 segments
The scolex
o Measures 1mm, globular in shape, has 4 cup-like
suckers.
and
quinacrine
TAENIA SOLIUM
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DIPHYLLOBOTHRIUM LATUM
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Common name: Broad or Fish
tapeworm
Disease:
Diphyllobothriasis,
bothriocephaliasis, Dibothriocephalus
anemia, fish tapeworm infection
Longest tapeworm of human measuring 3-10 meters in
length.
3,000-4,000 proglottids
Usual habitat of the worm is ileum and sometimes the
jejunum.
Scolex is small measuring 2-4mm in length by 10-12mm in
width.
Scolex is spatulate or almond-shape with 2 dorsoventral
sucking grooves.
Single worm may discharge as many as 1 million ova daily
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Terminate in muscular cirrus in a common genital pore.
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Symmetrically bilobed ovary
A vagina that extends from a common genital pore in the
midventral line.
The gravid rosette like or highly coiled uterus in the middle
of the gravid segment is a diagnostic characteristics.
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Rostellum
o Armed with double rows of large and small hooklets
approximately 20-25 in number.
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Mature proglottid
o Roughly square with irregularly alternate genital pores
opening from side to side in adjacent proglottids.
The testes
o Consist of 100-200 follicles, distributed throughout the
dorsal plane.
Ovary
o Situated in the posterior third of the proglottids.
o Consists of 2 large symmetrical lobes and an
accessory lobe on the side of the genital pore.
Gravid segment
o Contains uterus, which has 7-13 lateral uterine
branches.
o Each gravid segment contains 30,000-50,000 eggs.
o The gravid proglottids become detached from the
strobila in groups of five or six (in chain) and are
passed in the feces.
Mature egg
o Spherical, measure 30-45 microns.
o Pale buff to walnut brown in color. It has two radially
eggs shell.
o Oncosphere has three pairs of hooklets.
o The eggs of Taenia solium cannot be distinguished
from the eggs of Taenia saginata.
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MALE ORGANS
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FEMALE ORGANS
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EGGS
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Broadly ovoid with inconspicuous (not clearly
visible) operculum (small covering or lid).
Thick shelled, light golden brown with a knob
on the bottom of the egg.
It measures 58-76 microns and contain an
immature embryo when discharge in the feces.
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PATHOLOGY/DISEASE
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The scolex attached to the jejunum and competes with the
host for the available supply of Vitamin B12.
The blood picture is that of macrocytic anemia.
DIAGNOSIS
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DFS
Kato technique
To differentiate anemia due to diphyllobothriasis from
pernicious anemia, examination of the gastric juice for the
presence of free hydrochloric acid is useful.
PATHOLOGY
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Abdominal discomfort
Chronic indigestion
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TRANS:
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Diarrhea
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Concentration techniques
Perianal swabs
DIAGNOSIS
TREATMENT
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Praziquantel
Niclosamide
Cysticercus cellulosae
Larval infection of Taenia solium usually infects pig but
human can also be infected.
Ingestion of food and water contaminated by human waste.
Oral transmission by unclean hands of carriers of the adult
worms.
Cysticerci (cysticercus cellulosae) lodge in vital organs
such as brain, eyes, spinal cord, heart and liver giving rise
to pressure symptoms.
In the brain, it may produce hydrocephalus, meningitis,
cranial nerve damage, seizures, hydroactive reflexes and
visual defects.
Convulsions are the most common manifestations of
cerebral cysticercosis.
TAENIA SAGINATA
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Common name: Beef tapeworm
Disease caused: Beef tapeworm
infection/taeniasis
4-10 meters up to 25m
1,000-4,000 segments
Unarmed scolex
Irregularly alternate genital pores and
differ from Taenia solium in having as
many testes numbering 330-400
follicles and in lacking the accessory
ovarian lobe.
LIFE CYCLE
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Life cycle same as Taenia solium.
Intestinal disturbances may produce acute intestinal
obstruction.
Toward the end of the prepatent period, diarrhea and
hunger pains frequently develop and loss of weight may
occur.
The most common symptoms are discomfort and
embarrassment occasioned by the crawling of the
proglottids from the anus, with a strong tendency to crawl
during the day when the host is active.
DIAGNOSIS/TREATMENT
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Concentration techniques
Perianal swabs
Praziquantel
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Thorough cooking of meat
Sanitary inspection
Meat inspection
PREVENTION AND CONTROL
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