2. Phylum Platyhelminthes
(Flatworms)
Bilaterally symmetrical
Compressed dorso-ventrally
Has a definite
anteroposterior axis
They lack a circulatory
system
Some species are
hermaphroditic or
monoecious
Some are diecious
3. Possess a bilaterally
symmetrical excretory
system, collecting
tubules, and capillaries
which terminate in
“flame cells”.
4. Two classes under Phylum Platyhelminthes which
are of medical importance:
a. Class Cestoidea
b. Class Trematoda
5. Class Cestoidea
Cestodes or tapeworms
inhabit the small intestinal
tract of vertebrates while the
larva parasitize the tissues of
vertebrates and invertebrates.
Adult cestodes are usually
ribbon or tape-like segmented
parasites varying in size from
a few millimeters to several
meters.
The body consists of 3 distinct
regions:
Proglottids or segment:
a. Immmature- no well
developed organs
b. Mature- w/ well developed
organ
c. Gravid/ripe- filled with eggs
6.
7. The life cycle of cestodes include:
1. the egg with a hexacanth embryo
or oncosphere
2. the larval stage (cysticercus,
cysticercoid larvae, or coracidium,
procercoid and plerocercoid
larvae)
3. adult stage
All cestodes usually require an
intermediate host although in some
species the definitive host can
serve as intermediate host.
8. Two orders of tapeworms with medical importance:
Order
PSEUDOPHYLLIDEA
Order
CYCLOPHYLLIDEA
False tapeworm True tapeworm
example D. latum All except D. latum
scolex Spoon-shaped with slit-like
sucking grooves called
bothria
With 4 cup-like suckers
strobila Anapolytic (don’t shed
segments)
Apolytic (shed segments)
ova Operculated, immature
when laid
Non-operculated,
embryonated
Larval stages 1st: coracidium
2nd: procercoid
3rd: plerocercoid (IS)
1st: cysticercus
2nd: cysticercoid
3rd: hydatid
Intermediate host 2 1 only
9. Class Trematoda
Leaf-like and unsegmented
Adult trematodes are provided
with an oral sucker and a
ventral sucker called
acetabulum.
A third sucker called genital
sucker or gonotyl is observed
only among the heterophyids
10. The life cycle of trematodes includes:
1. The egg stage
2. The larval stages (miracidium, sporocyst, redia, cercaria,
metacercariae)
3. Adult
The definitive host (man) harbors the adult worm
Intermediate host usually a freshwater snail or mollusk harbors the
larval stage
2nd intermediate host (fish, crab, or another snail) is required for
encystment
11. Phylum Platyhelminthes
Class: Cestoidea (tapeworms)
Subclass: Cestodes
Order: Pseudophyllidea – scolex spatulate with bothria
1. Diphyllobothrium latum
Order: Cyclophyllidea- scolex globular with 4 cuplike suckers
A. Species which requires vertebrate intermediate hosts
1. Taenia solium
2. Taenia saginata
B. Species which require invertebrate intermediate hosts
1. Dipyllidium caninum
2. Hymenolepis diminuta
C. Species which may or may not require intermediate host
1. Hymenolepis nana
D. Species which may infect man in their larval stages
1. Echinococcus granulosus
2. Echinococcus multilocularis
12. Class: Trematoda (flukes)
A. Species which inhabit the portal blood stream of vertebrates
1. Schistosoma japonicum
2. Schistosoma mansoni
3. Schistosoma haematobium
B. Species which inhabit the liver of vertebrates
1. Fasciola hepatica
2. Clonorchis sinensis
3. Opistorchis felineus
C. Species which inhabit the small intestines of vertebrates
1. Fasciolopsis buski
2. Echinostoma ilocanum
3. Heterophyid group
D. Species which inhabit the lungs of vertebrates
1. Paragonimus westermani
14. Intestinal Cestodes
Taenia saginata Taenia solium
Common name Beef tapeworm Pork tapeworm
Intermediate host cattle Pig
scolex No rostellum Armed rostellum
length <25 m <7 m
# of uterine branches 15 or more 13 or less
# of proglottids 1000 to 2000 <1000
Gravid proglottid Tree-like ( dichomotous) Finger-like (dendritic)
eggs Spherical and striated, inside is an embryo or oncosphere
with 6 hooklets
larva Cysticercus bovis Cysticercus
cellulosae
Infective stage Cysticercus bovis Cysticercus
cellulosae
Pathogenesis Taeniasis saginata Taeniasis solium,
cysticercosis
17. Taenia species
The eggs of the two species cannot
be differentiated.
Differentiation is usually done by
examination of gravid proglottids
that have been injected with India
ink to reveal the lateral uterine
branches.
The eggs are spherical, yellow-brown
measuring 31-43 mm.
The shell is thick and radially
striated, giving it a "prismatic"
appearance.
The egg also contains a six-hooked
embryo called an oncosphere.
18. Hymenolepis
Hymenolepis nana Hymenolepis diminuta
Commin name Dwarf tapeworm
(smallest tapeworm)
Rat tapeworm
Scolex Armed rostellum Unarmed rostellum
eggs With 4 to 8 polar
filaments
Without filaments
Infective stage Eggs (direct)
Cysticercoid larvae
(indirect)
Cysticercoid larvae
Intermediate host Fleas (Ctenocephalides
canis, Xenopsylla
cheopis, Pulex iritans)
Flour beetles (Tenebrio
molitor, T. obscurus,
Tribolium confusum)
Insects
Final host man Norway rats
19.
20.
21. Dipylidium caninum
Dog tapeworm or double-pored
tapeworm
Producing dipylidiasis
very common intestinal
parasites of dogs and cats
Scolex is small w/ four
deeply cupped suckers an
protrusible rostellum
Armed w/ 1 to 7 rows of
rose-thorn shaped hooklets
22. The gravid proglottids have the
size and shape of the pumpkin
seed and are filled with
capsules or packets of about 8
to 15 eggs enclosed in a
embryonic membrane.
D. caninum egg packet, containing 8
visible eggs, in a wet mount
23. Diphyllobothrium latum
Fish tapeworm/ broad tapeworm
Producing dyphillobothriasis
Scolex is spatulate and measures 2-
3mm in length by 1mm in diameter
It has two bothria or sucking grooves
24. The dark, rosette-like, coiled
uterus located in the middle of
the gravid proglottid
Ova are usually
yellowish brown, w/ a
moderately thick
shell and an
inconspicuous
operculum.
25. Extraintestinal Cestodes
Echinococcus sp.
Belong to the Family Taeniidae, Order Cyclophyllidea
Echinococcus granulosus
Cause cystic echinococcosis
Echinococcus multilocularis
Cause alveolar echinococcosis
26. Echinococcus granulosus
Hydatid worm
Causes hydatid
disease
The smallest
tapeworm (consisting
only of a pyriform
scolex, neck and three
segments)
Three segments: one
immature, one mature,
and one gravid
The scolex bears a
prominent rostellum
and has four acetabula
27. Definitive host:
dogs and other
canines
Intermediate host:
goats, horses,
camels, and sheep
Larval stage: hydatid
cyst
- numerous
protoscolices may
be found within the
cyst
- cyst has outer
laminated layer and
inner nucleated
germinal layer
When protoscolices and broad capsules
lie free in the cyst, these are referred to as
“hydatid sand”.
28. Pathogenesis and Clinical Manifestations
Liver (right lobe) – the most common and most
important site of involvement
Unilocular hydatid cyst – cyst of E. granulosus
Alveolar cysts – cyst of E. multilocularis
Osseous hydatid cyst- Unilocular cyst when located in
the bone
E. granulosus has led to down regulation of
inflammatory cytokines leading to a local
immunosuppression
Hepatic cyst – mostly found in the inferior right lobe
and may cause obstructive jaundice
Abdominal cyst – may cause discomfort when the
cyst are large enough
29. The rupture of hepatic cyst produces a characteristic
triad: intermittent jaundice, fever, and eosinophilia.
Sputum may contain frothy blood, mucus, hydatid
fluid and bits of membrane.
Involvement of the brain may cause increased
intracranial pressure and Jacksonian epilepsy.
Jacksonian seizures are partial seizures that begin in one part of the
body such as the side of the face, the toes on one foot, or the fingers on
one hand. The jerking movements then spread to other muscles on the
same side of the body. This type of seizure is associated with a lesion or
defect in the area of the cerebral cortex that controls voluntary
movement
30. It shows multiple destructive cystic lesions in the proximal of the tibia and distal of the femur which some of them show extra-osseous extension.
Enlargement of the head in a 5-year-old male
who was finally diagnosed to have brain hydatid
disease.
Extra –osseus extension in the knee
31. Diagnosis
1. Roentgenogram
2. Exploratory cyst puncture
3. Immunologic tests (intradermal, precipitin,
complement fixation, hemagglutination, and
bentonite flocculation latex slide agglutination and
fluorescent antibody tests)
4. Serologic tests ( IHA, IFA, EIA)
Positive cases will have to undergo a gel diffusion
assay that would demonstrate the echinococcal “Arc
5” for confirmation.
32. Sparganosis
Refers to the larval infection with the plerocercoid
larvae also known as spargana of pseudophyllidean
tapeowrms falling under the Genus Spirometra.
Common in man: Spirometra mansoni
Spirometra erinacei
Spirometra ranarum
33. Trematodes (Flukes)
All FLUKES Schistosomes
shape Flat and leaf-shaped Elongated and
cylindrical
sexes hermaphroditic Separate sexes
egg operculated Nonoperculated
transmission ingestion Skin penetration
Infective stage metarcercaria Cercaria
Intermediate host 2 1
•Attaches to host by means of 2 suckers:
oral sucker and ventral sucker (acetabulum)
•Heterophyes has 3 suckers, the 3rd one is the genital sucker
(gonotyle)
34. Life cycle:
1. egg stage
2. larval stage
a. 1st intermediate: miracidium-sporocyst-redia-cercaria
b. 2nd intermediate host: cercaria-metacercaria
3. adult stage
Requires 2 intermediate hosts (except for
Schistosomes)
1st IH: snail
2nd IH:
a. fish – H. heterophyes, C. sinensis, O. felineus
b. crab – P. westermanni
c. plant/vegetation – F. hepatica, F. gigantica, F.
buski
d. snail: E. ilocanum
35. Lung Fluke
Paragonimus westermanni
Common name: Oriental lung fluke
Causing : paragonimiasis, lung fluke disease,
pulmonary distomiasis, endemic hemoptysis, parasitic
hemoptysis
Two other species:
P. philippinensis
P. siamensis (only in cats)
39. Pathogenesis and Clinical
Manifestations
Heavy infections: from dry cough and later produce
bloodstained or rust- colored sputum with foul fish
odor, most pronounced in the morning.
Elevated levels of IL-5
Migration in the brain may cause: Jacksonian
epilepsy, cerebral hemorrhage, edema, visual
disturbances, or meningits
Often misdiagnosed as PTB
40. Diagnosis
Radiographs
Complement fixation (CF) – standard serological test
Enzyme Immunoassay (EIA)
Immunoblot (IB)
Based on the detection of characteristic eggs in the
stool
41. Intestinal Flukes
Fasciolopsis
buski
Common name:
Giant intestinal
fluke
Causing:
fasciolopsiasis
*The largest fluke
parasitizing man
Adult:
-does not have
cephalic cone
43. First intermediate host:
-snails belonging to the
genus Segmentina or
Hippeutis
Second intermediate
host:
Trapa bicornis (water
caltrop)
Eliocharis tuberosa
(water chesnut)
Ipomea obscura (water
morning glory)
Nymphaea lotus (lotus)
Definitive host:
Humans
Pigs
44. Pathogenesis and Clinical
Manifestations
Pathological changes are traumatic, obstructive, and
toxic.
Inflammation and ulceration
Heavy infections: intestinal obstruction
Toxic and allergic symptoms: edema in the face,
abdominal wall, and lower limbs
Profound intoxication can result to death
Diagnosis
Detection of parasite in stool
45. Echinostoma ilocanum
Artyfechinostomum malayanum
The echinomastids are digenetic trematodes
characterized by a collar of spines around their oral
suckers.
A. Malayanum adult
- Has rounded posterior end
- 43-45 collar spines
- Two testes: large w/ six to nine lobes arranged in
tandem
A. Malayanum egg
- Larger
- golden brown in color
- operculated
46. E. ilocanum adult
- Reddish-gray
- Tapered posterior end
- Has 49 to 51 collar
spines
- testes: deeply
bilobed, arranged in
tandem
E. ilocanum egg
- straw-colored
- operculated
Echinostoma ilocanum:
Common name: Garrison’s fluke
Causing: echinostomiasis
47. E. ilocanum
First snail intermediate host:
Gyraulus convexiusculus
Hippeutis umbilicalis
Second snail IH:
Pila luzonica (kuhol)
Vivipara angularis (susong pampang)
A. Malayanum
Second snail IH:
Lymnaea(Bullastra) cumingiana(birabid)
48. Pathogenesis and Clinical Manifestations
Ulceration
Diarrhea (sometimes bloody)
Abdominal pain
Diagnosis
Detection of eggs in the stool
50. Heterophyes heterophyes
Common name: Von
Siebod’s fluke
*smallest fluke of man,
yet deadliest.
Adult:
- elongated, oval or
pyriform
- Tegument has fine
scale-like spines
Egg:
- Light brown in color
- ovoid
52. Blood Fluke
Schistosomes:
S. japonicum – aka as Oriental Blood
fluke
- causes Katayama’s disease
- habitat: mesentric veins of small
intestines
- IH: Oncomelania quadrasi
53. S. mansoni – smallest blood fluke
- habitat: mesentric veins of colon, rectum
- IH: Biophalaria and Australorbis
S. haematobium – aka as Vesical blood
fluke
- causes: Bilharziasis or uninary
schistosomiasis (bloody urine)
- habitat: veins of urinary bladder
- IH: Bulinus and Physopsis
54. S. japonicum & S. mansoni
- parasites of branches of the portal vein
- both cause primarily hepato-intestinal
schistomiasis
S. haematobium
- inhabits the veins of the urinary bladder
- causes urinary schistosomiasis
55.
56. Ovum
S. japonicum
- ovoidal, rounded or
pear-shaped
- when recovered in
stool, the eggs are
pale yellow
- on the side near one
of the polar ends is
a curved hook or
spine.
57. S. mansoni
- a prominent lateral
spine near the
posterior end.
- the anterior end is
tapered and slightly
curved.
60. Miracidium
-morphological
features includes:
apical papilla
epidermal plates
covered w/ cilia
pair of cephalic
unicellular
penetration glands
two pairs of flame
cells & germinal cells
61. Miracidium
- are phototactic and swim actively in surface
water
- factors which influence the infection of snail
by miracidia:
- age of snails & miracidia
- number of miracidia per snail
- length of contact time
- water flow & turbulence
62. Intramolluscan Developmental Stages
- the miracidium becomes the first generation or
mother sporocyst soon after penetration of its
snail host.
- in 96 hours, it is an elongated sac filled with
germinal cells.
- on the 8th day, germ cells budded off and
develop into daughter sporocyst.
63. Cercariae
- mature cercariae emerge from daughter sporocysts
and escape from the snail into surrounding waters.
- the cercariae has a body and a forked tail, oral and
ventral sucker.
- elongated body: 100 to 500 um in length
40 to 60 um in diameter
- tail trunk: 140 to 150 um by 20 to 35 um
- fork: 50 to 70 um long
- cercarial penetration is mediated by lytic enzymes
secreted by cephalic glands aided by muscular
activity.
64.
65. Schistosomule
- after skin penetration,the cercaria is transformed
into a schistosomule, which has different
physiological adaptations and requirements.
66. Adult flukes
- unlike other trematodes, schistosomes have separate
sexes.
- adults:
large sucker capping the anterior end
ventral sucker
gonophore
- the suckers aid in the movement and enable the flukes
to maintain their position inside the veins.
- male: shorter but sturdier sex
- 12-20 mm in length by 0.4 o -0.5 mm in
diameter
- female: measures 15 to 26 mm by 0.3 mm
67. male:
-also has a
gynecophoral canal
where the longer
and more slender
female is held.
68. Pathogenesis and Clinical
Manifestations
Early Schistosomiasis
- chills, fever or non-productive cough
Colonic Schistosomiasis
- ulcerations result in dysentery or diarrhea
Hepatosplenic Disease
- the most serious consequence of chronic
schistomiasis
- characterized by hepatosplenomegaly, ascites, and
collateral circulation
69. Pulmonary Schistosomiasis
- cor pulmonale resulting from the obstruction of
the pulmonary vasculature
Cerebral Schistosomiasis
- meningoencephalitis with fever, headache,
confusion, lethargy, and coma.
70.
71.
72. Hepatosplenic schistosomiasis
Collateral circulation
Patients infected with a large load of parasites are
more likely to produce disease in the liver. The
eggs of the parasite tend to migrate and settle in
the portal vein, causing inflammation and
obstruction of the passage of blood by fibrosis.
As all the blood coming from gastrointestinal
system passes through the portal vein to the
liver before going to the rest of the body, an
obstruction in this region causes a huge "traffic
jam" of blood, which leads to what we call portal
hypertension. If no blood reaches the liver, it has
to find other ways to get to the rest of the body,
forming a collateral circulation.
Portal hypertension is responsible for
complications of hepatosplenic schistosomiasis,
among them, ascites, splenomegaly (enlarged
spleen) and esophageal varices. The
esophageal varices are a feared complication of
portal hypertension, as they may rupture
causing severe gastrointestinal bleeding and
bloody vomiting.
73. Liver Flukes
- these are digenetic trematode species
belong to family Fasciolidae.
- they are parasites found in the liver and
biliary passages of humans and herbivorous
mammals, especially ruminants.
- in tropical countries, fascioliasis is
considered the most important helminth
infection of cattle.
74. First intermediate host:
- belongs to the family Lymnaeidae
- L. philippinensis & L. auricularia
rubiginosa
Second intermediate host:
- aquatic plants:
Ipomea obscura (kangkong)
Nasturtium officinale (water cress)
75. Fasciola hepatica
- common name: sheep liver fluke
- causes: sheep liver rot, fascioliasis hepatica
- prevalent in sheep raising countries
Fasciola gigantica
- common name: Giant liver fluke
- infects cattles in the Philippines
76.
77. egg
-large, ovoidal,
operculated and
yellowish to
brownish in color
-measures: 140-
180 um by 80-
100 um in size
-released from the
worm still
immature
78.
79. Pathogenesis and Clinical
Manifestations
-two clinical stages:
1. Acute stage
- coincides with larval migration and worm
maturation in hepatic tissue.
2. Chronic stage
- coincides with the persistence of Fasciola
worms in the biliary ducts
80. Hepatic fascioliasis:
-can be asymptomatic or may produce fever
-right upper quadrant abdominal pain
-hypereosinophilia
Fibrosis when the worm reached the bile
ducts
Pharyngeal fascioliasis or Halzuon
(suffocation) has been reported in
Mediterranean countries.
This has been attributed to ingestion of raw
liver containing the parasites w/c attach to the
pharyngeal mucosa causing asphyxiation.
81. Clonorchis sinensis
Opisthorchis felineus
Opisthorchis viverrini
- belong to family Opistorchiidae
- parasites of the bile duct and
gallbladder of humans and fish-eating
mammals
82. Clonorchis sinensis
-common name: Chinese liver fluke
Oriental liver fluke
-causes: clonorchiasis
-most important liver fluke in man
-eggs are like old fashioned electric light bulb
Opisthorchis felineus
-common name: cat liver fluke
-causes: opistorchiasis felineus
83. First snail intermediate host of C. sinensis:
- belong to the genera Parafossarulus
P. manchouricus, P. anomaloispralis, P. stratulus
- genera Bulimus (B. striatulus)
- genera Semisulcospira
- genera Alcinma (A. longicornis)
- genera Thiara ( T. granifera)
- genera Melanoides (M. tuberculatus)
First snail intermediate host of O. felineus and
O. viverrini:
- genus Bithynia
