CESTODES
Nadine Joyce T. Roa, RMT
INTESTINAL CESTODES
Taenia spp.
Taenia saginata
Beef tapeworm
Adult - 4 to 10 m in length and
may have 1,000 to 4,000
proglottids.
Scolex - has four prominent
acetabula
Mature proglottids
- Square in shape.
- Contain mature male and female
reproductive organs.
- There are two large lobes of
ovaries and a median club-shaped
uterus
- Follicular testes 300-400 are
scattered throughout.
- The vagina has sphincter.
- Most distal from the neck
Taenia saginata mature gravid
Taenia saginata gravid
EGG
● ova are spherical or sub
spherical in shape, measuring
30 to 45 µm in diameter
● The ova are brownish in
color, with a thick
embryophore which appears
striated.
● Inside the eggshell is the
oncosphere or embryo
provided with three pairs of
hooklets
Taenia spp.
Taenia solium
● Pork tapeworm
Adult - measure 2 to 4 m in length
and may have 8,000 to 10,000
proglottids.
Scolex - has four acetabula, but it is
smaller (1 mm) and more spherical
that that of the beef tapeworm
-carries a cushion-like rostellum with
a double crown of 25 to 30 large and
small hooks.
● presence of an accessory ovarian
lobe,
● the absence of a vaginal sphincter,
and
● the smaller number of follicular
testes (100- 200) in the mature
proglottid of T. solium.
● Proglottids are relatively less active
than the proglottids of T. saginata.
● Gravid proglottid contains
approximately 30,000 to 50,000 ova.
Taenia solium mature gravid
Diagnosis
● Specific diagnosis rests on identifying the characteristic proglottids,
eggs or scolex
● Examination of the stool can be done for the presence of eggs,with
the stools.
● Concentration techniques like the formalin-ether/ethyl acetate
concentration technique
● Perianal swabs may also be useful because eggs are left in the
perianal skin as the gravid segments squeeze out of the anal
opening
● Neurocysticercosis may be suspected in a patient coming from
an endemic area with epileptic seizures without associated
systemic symptoms.
● Computed axial tomography (CAT) scans and
● nuclear magnetic resonance imaging (MRI)
● Serologic tests include
○ serum and CSF enzyme-linked immunosorbent
assay (ELISA)
○ electro-immuno transfer blot (EITB)
○ or Western blot for specific IgG and IgM
○ anticysticercal antibodies.
Taenia spp.
Taenia asiatica
Has been reported in Taiwan, Korea, Thailand, and
Indonesia.
Adult -may vary between 4 to 8 m with 300 to 1,000
segments.
Scolex - Similar to Taenia saginata, the scolex is devoid of
hooklets but there is a prominent rostellum.
Gravid - have posterior protuberance with 11 to 32 lateral
branches arising from the main uterus
Hymenolepis nana
Dwarf tapeworm
Smallest tapeworm
Adult - with a delicate strobila measuring
from 25 to 45 mm in length and 1 mm in
width
Scolex - subglobular with four
cup-shaped suckers
Retractable rostellum armed with a single
row of 20 to 30 Y-shaped hooklets.
Gravid
- No more than 175 to 220
segments compose the
entire length of the strobila.
- Mature proglottids contain
three ovoid testes and one
ovary in a more or less
straight pattern across the
segment.
Gravid Proglottid (left) Mature Segment (right)
EGGS
● are spherical or subspherical,
colorless or clay-colored, measuring
30 to 47 μm in diameter
● oncosphere has a thin outer
membrane and a thick inner
membrane with conspicuous bipolar
thickenings,
● four to eight hair-like polar
filaments embedded in the inner
membrane.
● Smoother outer shell
● Six-hooked (hexacanth)
oncosphere
Diagnosis
● Demonstration of eggs in stool.
● Concentration techniques.
Hymenolepis diminuta
Rat tapeworm
Adult - larger than H. nana. The worm measures
about 60 cm in length
Scolex - having a rudimentary unarmed
rostellum
Gravid
- Larger and may reach 0.75
mm in length and 3.5 mm in
width
- three ovoid testes and one
ovary in a more or less
straight pattern across the
segment.
EGGS
● circular, about 60 to 80 μm in
diameter and are bile-stained.
● The oncosphere is enclosed
in an inner membrane, which
has bipolar thickenings but
lacks the bipolar filaments.
● Hooklets usually have a
fan-like arrangement.
A, Hymenolepis nana. B, Hymenolepis diminuta
Dipylidium caninum
Very common intestinal parasite of
dogs and cats
double-pored tapeworm
Adult - pale reddish adult worm
measures 10 to 70 cm in length
Scolex - is small and globular with
four deeply cupped suckers and a
protrusible rostellum, which is armed
with one to seven rows of rose
thorn-shaped hooklets.
Proglottids
- are narrow with two sets of
male and female reproductive
organs and bilateral genital
pores,
- gravid proglottids have the size
and shape of a pumpkin seed
and are filled with capsules or
packets of about 8 to 15 eggs
enclosed in an embryonic
membrane
EGGS
● spherical, thin-shelled with a
hexacanth embryo
Diagnosis
● Recovery of gravid
proglottids segments.
Mature segment (left) Proglottid (right)
D. caninum Details of a mature proglottid (left) where the egg capsules (centre) can be seen,
containing the oncospheres with hooks (right).
Raillietina garrisoni
Tapeworm of rats.
is about 60 cm in length with a minute, subglobular
scolex with four acetabula.
rostellum is armed with two alternating circular rows of
90 to 140 hammer-shaped hooks
Diagnosis - finding proglottids or ova in stool.
Diphyllobothrium latum
Dibothriocephalus latus
Fish tapeworm or broad
tapeworm.
Adult - measures from 3 to 10 m
in length and may have 4,000
proglottids.
Scolex - spatulate and measures
2 to 3 mm in length by 1 mm in
diameter.
EGG
Usually yellowish brown, with
a moderately thick shell and
an inconspicuous operculum.
Opposite the operculum is a
small knob-like thickening.
Diagnosis
Residence in or travel to an endemic area.
Raw-fish diet.
finding the characteristic operculated eggs or on
occasion, proglottids in stools.
proglottids are wider than long and show a typical rosette-shaped uterus,
visible in the middle of each proglottid
Mature Segment (left), Gravid segment (right)
Operculated egg (arrow head), never embryonated when passed in the faeces. At the
abopercular end, a knob (arrow) can sometimes be seen.
EXTRAINTESTINAL CESTODES
Echinococcus spp.
E. granulosus and E.multilocularis cause cystic echinococcosis
and alveolar echinococcosis
E.vogeli and E. oligarthrus both cause polycystic
echinococcosis.
Adults - inhabits the small intestines of canines. It measures 3
to 6 mm in length and possesses a pyriform scolex, a short
neck, and three proglottids: one immature, one mature, and one
gravid.
Scolex - it has four acetabula. It is armed with 30 to 36 hooks.
Hydatid cysts - measure
1 to 7 cm in diameter. The
cyst has an outer
laminated hyaline layer
and an inner nucleated
germinal layer.
Diagnosis
Radiographic findings or ultrasonography, combined with
a history of residence in an endemic area, and close
association with dogs are important in the diagnosis of
echinococcosis.
Positive serologic tests, such as the use of indirect
hemagglutination (IHA), indirect fluorescent antibody
(IFA) test, and enzyme immunoassays (EIA)
Spirometra spp
Commonly involved in human sparganosis are Spirometra
mansoni, Spirometra erinacei, and Spirometra ranarum.
intestinal parasites of cats, dogs, and other carnivores.
Gravid - proglottids of Spirometra sp. have a spiral uterus,
Eggs - are operculated and immature, similar to those of
Diphyllobothrium, although smaller.
Diagnosis
Sparganosis is diagnosed through the recovery of
the plerocercoid larvae from infected tissues.
Species identification, however, can only be done
through experimental animal infection.