Phylum
Platyhelminthes.
Class Trematoda.
Class Cestoda.
Phylum
Nemathelminthes
By Pryvrotska
I.B.

According to the way of development
parasites are classificated into
biohelminthes and geohelminthes.

Geohelminthes develop without
intermediate hosts.

Biohelminthes have complete life cycle
with intermediate hosts.
The flatwotms consists of some 12, 200
species, including classes of parasitic
worms: Trematoda, Cestoda

General characteristic of Flatworms

All flatworms are acoelomate, triploblastic, and
bilaterally symmetrical.

flattened dorsoventrally

they have a definite head at the anterior end.

The most of flatworm species, in all three classes,
are hermaphrodites. A single individual generally
cannot fertilize itself, although exceptions do exist.
General characteristic of Class
Trematoda
- Flattened dorsoventrally
(leaf-like).
- Unsegmented.
- Body is covered by cuticle.
- Organs of fixation: oral
sucker, ventral sucker.
- Genital system: Trematodes
are hermaphrodites except
genus Schistosoma.
-The life cycle is passed in two
hosts (alternation of hosts)
BLOOD FLUKES - genus
SCHISTOSOMA

Distribution: Africa, Asia, Middle
East, Latin America.




Schistosoma mansoni and
Schistosoma japonicum cause
Hepatosplenic Schistosomiasis.
Schistosoma haematobium causes
Urinary Schistosomiasis.
Localization: venous vessels of
bowel, liver, and bladder.
Morphology: atypical trematodes
which the adult female nesting within
a specialized groove in the body of
the larger male.
BLOOD FLUKES

Transmission: infection
through skin of larvae from
snail hosts.

Infective stage: cercariae.

Intermediate host: snail.

Definitive host: man.

Mode of transmission:
penetration of skin by
cercarie.
BLOOD FLUKES

Clinical
manifestations
of
Hepatosplenic Shistosomiasis:

Clinical manifestations of
Urinary Schistosomiasis:

eosinophilia,
granulomatous polyps in colon,
Fever,
anorexia, weight loss,
anemia,
portal hypertension,
dysentery and cirrhosis of liver,
pruritic skin rash.
Eggs go back through portal
circulation to liver, causing
hepatomegaly, liver tenderness.

eosinophilia,
hematuria,
terminal dysuria (pain,
difficulty at the end of
urination);
obstructed urine flow.
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Laboratory diagnostics and
Prevention:

Hepatosplenic
Schistosomiasis:
with lateral spine in feces.



Laboratory diagnostics of
Schistosomiasis: eggs with
eggs
Urinary
terminal
spine in urine
Prevention: involves proper disposal of
human waste and eradication of the snail
host when possible.
Swimming in endemic areas should be
avoided.
LUNG FLUKE: PARAGONIMUS
WESTERMANI –
an agent of paragonimiasis

Distribution: Far East,
Central America, Africa,
and India.
 Morphology: an egglike form of the body,
from 7,5 to 16 mm.
LUNG FLUKE


Mode of transmission:
ingestion of metacercarial cysts
in crabs or crayfish.
Final hosts: carnivorous
mammals, pigs, humans.

Intermediate hosts:

1) snail (sporocyst, redia,
cercaria);
2) crabs or crayfish
(metacercaria).
Infective stage: metacercariae


LUNG FLUKE

Clinical disease: a chronic cough with bloody

sputum, dyspnea, pleuritic chest pain, and
pneumonia.
Laboratory diagnosis: eggs in sputum or feces.
Prevention: cooking crabs and crayfish
properly.

BILIARY (LIVER) FLUKES
FASCIOLA HEPATICA an agent of
fascioliasis.

Distribution: endemic in Far
East.
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bile
ducts,
gallbladder, and pancreas.
Morphology: large size (3-5 cm)
and conical form of the body
sucking disks (oral and abdominal)
Multibranched uterus is situated
under the abdominal sucking disk.
Testis are branched too and located
in the middle part of the body.
Localization:
FASCIOLA HEPATICA

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Life-cycle:
Final
host
herbivorous
mammals
(horses) and humans.
Intermediate host —
the
snail
Limnea
truncatula.
Transmission: fecaloral

Invasive
adolescariae.
stage:
FASCIOLA HEPATICA




Clinical
disease:
Parasites obstruct bile ducts
and lay eggs within them,
leading to cholelithiasis
(gallstones).
Biliary obstruction can
occur, sometimes causing
biliary cirrhosis.
Diagnosis:
immature
eggs in feces.
Prevention: involves not
eating
wild
aquatic
vegetables.
OPISTHORCHIS FELINEUS
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Opisthorchiasis.
Distribution: Siberia.
Morphology:
flat, the length of the body 4-13
mm.
In the middle part of the body
there is a branched uterus.
Behind it there is a round ovary.
roseolla-like testis in the back of
the uterus - a diagnostic sign of
this worm.
OPISTHORCHIS
FELINEUS
Life-cycle:
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Final host - carnivorous
mammals and humans.
Intermediate host
1) - snail Bithynia leachi genus
2) - fish.
Transmission: ingestion of
fish, which contains
metacercariae.

Invasive stage:
metacercariae cysts in fish
muscles.

Localization: bile ducts,
gallbladder, liver.
OPISTHORCHIS
FELINEUS
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Clinical disease:
cholecystitis and cholelithiasis,
hepatic colic, cirhosis.
Infection can lay dormant for several years before
presenting clinically.
Diagnosis: immature eggs in feces, in fluid from
biliary drainage, or duodenal aspirate.
Prevention involves not eating undercooked or
contaminated raw, frozen, dried, pickled, and salted
fish; eradication of snail hosts when possible.
DICROCOELIUM LANCEATUM –
causes Dicrocoeliasis.
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Distribution: worldwide.
Localization: bile ducts, gallbladder
and liver of mammals (cattle,
horses). Very rare in humans.
Morphology: the worms are 1 cm
long with lanceolate form of the
body;
Two round testis are situated in
the front of the body - the
diagnostic sign of this worm.
Transmission: ingestion of plants
with the ants, which contain
metacercariae.
DICROCOELIUM
LANCEATUM

Invasive stage: metacercariae.

Life-cycle:

Final host - herbivorous mammals (cattle,
horses).
intermediate host
1- the snail of Zebrina and Helicela
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genus,
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2- the ants Fornica genus.
Clinical disease: is similar to fascioliasis.
Diagnosis: immature eggs in feces.
Prophylactics: eradication of the snails,
ants when possible; dehelmithization
of cattle.
Tapeworms (Cestoda)
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
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scolex, strobila or chain of
proglottids (multiple segments)
of varying stages of maturity.
They have no digestive tract
The cestodes receive all of its
nutrients be the tegument.
The scolex has specialized means
of attaching to the intestinal wall,
namely suckers, hooks, or sucking
grooves.

All cestodes have stage of larva
and stage of oncosphere in the life
cycle.
Taenia solium

The adult T. solium -taeniasis solium.
T. solium larvae cause cysticercosis.

Distribution Teniasis and cysticercosis

occur worldwide .

Morphology

scolex with 4 suckers and circle of
hooks
gravid proglottids, which have 7-12
primary uterine branches.
Larva of T.solium called cysticercus.
A cysticercus consist of a pea-sized
fluid-filled bladder with an invaginated
scolex.
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Taenia solium
Life cycle
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Transmittion: fecal-oral
Invasive stage:
cysticerci.
Definitive hosts –
humans
Intermediate hosts pigs
Humans can be
infected by eating raw
or undercooked pork
containing the larvae
cysticercus.
Taenia solium

The cysticerci can become large in eye,
subcutaneous tissue, brain, lung, heart,
and muscle. In the brain, they manifest as
a space-occupying lesion.
Taenia saginata
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
taeniasis saginata.
Distribution: occur worldwide
Morphology.
scolex with 4 suckers without
hooklets.
proglottids have 17-35 primary
uterine branches. Larva of
T.saginata called cysticercus.
Transmittion: fecal-oral
Invasive stage: cysticerci
Life cycle.
 Definitive hosts -humans
 Intermediate hosts - cattle Humans
can be infected by eating raw or
undercooked beef containing larvae.
Laboratory diagnosis: gravid proglottids
(with 17-35 uterine branches) may be
found in the stools.
 Prevention. Prevention of taeniasis
saginata involves cooking beef
adequately and preventing cattle from
ingesting human feces by disposing of
waste properly.


Clinical manifestation of teniasis
saginata:
abdominal pain,
 nausea,
 diarrhea,
 weight loss,
 infection may by asymptomatic.
 In some, proglottids appear in the
stools and may even protrude from
the anus.

Diphyllobothrium latum, the fish tapeworm,
causes diphyllobothriasis
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Distribution: Scandinavia, northern
Russia, Japan, Canada, USA.
Morphology.
scolex with 2 elongated sucking
grooves.
The proglottids are wider than they
are long, and the gravid uterus is in
the form of a rosette.
Adult worm is the longest of the
tapeworms, up to 13 m.
Larva called plerocercoid.
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Transmittion: fecal-oral.
Invasive stage:
plerocercoid.
Definitive hosts- humans .
Intermediate hosts
-1)copepod crustacea
-2) freshwater fish
Humans
infected
by
eating
raw
or
undercooked
fish
containing plerocercoids

Clinical disease: little damage in the small intestine.

megaloblastic anemia occurs as a result of vitamin
B12 deficiency caused by preferential uptake of the
vitamin by the worm.
Most patients are asymptomatic, but abdominal
discomfort and diarrhea can occur.
Diagnosis depends on finding the typical eggs, oval,
yellow-brown eggs with an operculum (lidlike
opening) at one end, in the stools.
Prevention involves adequate cooking of fish and
proper disposal of human feces.
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Hymenolepis nana (dwarf tapeworm) is found
worldwide, commonly in the tropics.
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Morphology. It is only 2-3 cm in
length. Scolex has round form and
contain suckers and hooks.
A neck is very long and thick.
Strobila has 200 proglottides.
The uterus has an excretory ostium.
Eggs are released from it into the
feces.
Transmission: fecal-oral (by the
ingestion of eggs from contaminated
food or water).
Invasive stage: egg.
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Life cycle.
The eggs of H. nana are directly
infectious for humans;
ingested eggs can develop into adult
worms without an intermediate host.
Within the duodenum, the eggs hatch
and differentiate into cysticercoid larvae
and then into adult worms.
Gravid proglottids detach, disintegrate,
and release fertilized eggs.
The eggs either pass in the stool or can
reinfect the small intestine
(autoinfection). A lot of H.nana worms
(sometimes hundreds) are found.
Clinical disease:
asymptomatic, but
diarrhea and abdominal cramps may be
present.
 Diagnosis can be proved by observing
eggs in stool.
 Prevention consists of good personal
hygiene and avoidance of
fecal
contamination of food and water.

Echinococcus granulosus (dog tapeworm)


Mediterranean region, the Middle East, and
Australian, USA (western states).
Morphology. Worm is up to 3-5 mm. Scolex has
suckers and hooks. A neck is short. Strobila has 35 proglottides. Posterior segment (mature) is the
largest and contains uterus with the haustrums,
genital pore situated in the back of the proglottid.

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Transmission: fecal-oral
Invasive stage: egg
Life cycle.
Definitive hosts: dogs.
Intermediate hosts: sheep,
humans.
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Diagnosis: made by Clinical
manifestations. asymptomatic,
but liver cysts may cause hepatic
dysfunction. Cysts in the lungs
can erode into a bronchus,
causing bloody sputum, end
cerebral cysts can cause
headache and focal neurologic
sings.
Diagnosis: made by routine Xray, observation of eosinophilia,
serologic tests.
Prevention of human disease
involves not feeding the entrails
of slaughtered sheep to dogs.
Echinococcus multilocularis


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Distribution: is found in
northern Europe, Siberia,
Canada, the USA.
- the definitive hosts are
mainly foxes and the
intermediate hosts are various
rodents.
Humans are infected by
accidental ingestion of food
contaminated with fox faeces.

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The disease occurs primarily in
hunters and trappers. Within the
human liver, the larvae form
multiloculated cysts with few
protoscoleces,
proliferate,
producing a honeycomb effect
of hundreds of small vesicles
(without fluid).
The clinical picture usually
involves jaundice and weight
loss. The prognosis is poor.
Nematodes
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Roundworms with a cylindrical body and a
complete digestive tract including mouth and
anus.
They are unsegmented, pseudocoelomate worms.
The body is covered with a noncellular, highly
resistant coating called a cuticle.
Nematodes have separate sexes; the female is
usually larger than the male. The male typically
has a coiled tail.
The medically important nematodes can be
divided into 2 categories: intestinal and tissue
nematodes.
Ascaris lumbricoides
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causes ascariasis.
Distribution: worldwide.
Morphology: Adult worms are
creamy or pink, spindleshaped, covered by striated
cuticle.
Adult male about 20 cm in
length, posterior end is
curved ventrally;
Adult female about 25-40 cm
in length, posterior end is
straight.
Eggs are brown, oval,
covered by membranes. An
external membrane is
tuberous
Ascaris lumbricoides

Mode of transmission: fecal-oral
(alimentary). Humans are infected by
eating eggs in soil contaminated with
human feces.
Ascaris lumbricoides
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Clinical manifestation:
- larvae may lead to pneumonia, eosinophilia.
- Adults -intestinal obstruction, penetration of the
intestinal wall, occlusion of the bile duct, the
pancreatic duct or the appendix, toxic effects
(nausea, vomiting). Most infections are
asymptomatic.
Laboratory diagnosis: microscopic
examination of faeces (eggs are oval with an
irregular surface); larvae may be found in
sputum.
Prophylaxis:
washing hands before meals;
proper washing of vegetables eaten raw;
treatment of patients;
proper disposal of feces;
health education.
Enterobius vermicularis




causes enterobiasis.
Distribution: worldwide.
Morphology: Adult
female worms are up to
10 mm in length, and
male worms are up to 5
mm.
Eggs are transparent
and colourless,
asymmetrical, with thin
and smooth membrane,
40-60 micro;m.
Enterobius vermicularis

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
Mode of transmission: fecal-oral (alimentary).
Infective stage: eggs.
The adult pinworms live in the large intestine
approximately 30 days.
After fertilization female worm migrates from the
anus and releases thousands of fertilized eggs on
perianal skin.
Within 6 hours, eggs develop into larvae and
become infectious.
Reinfection can occur if they are carried to the
mouth by fingers after scratching of the itching
skin.
Enterobius vermicularis



Clinical manifestation: Infection is frequent
among children under 12 years of age.
Perianal pruritus (itching) is most common
symptom.
Laboratory diagnosis: the eggs are
recovered from perianal skin by using the
“Scotch tape” technique and can be
observed microscopically (eggs are not
found in the stools). Seldom adult worms can
be found in the stools.
Prophylaxis: keep sanitary condition,
treatment of patients
Trichuris trichiuria




causes trichocephaliasis
(whipworm infection).
Distribution: worldwide,
especially in the tropics.
Morphology: Adult female
worms are up to 5,5 cm in
length, and male are up to
4 cm. The anterior end of
the body is hairlike.
The eggs are brown,
barrel-shaped with a plug
at each end, 20-50
micro;m in size.
Trichuris trichiuria


Mode of
transmission:
fecal-oral
(alimentary).
Infective stage:
eggs.
Trichuris trichiuria







Pathogenesis and clinical manifestation: Adult
worms burrow their hairlike anterior ends into the
intestinal mucosa. They feed blood. Trichuris may
cause diarrhea, abdominal pain, nausea, acute
appendicitis. Most infections are asymptomatic.
Laboratory diagnosis: microscopic examination
of feces (finding the typical eggs).
Prophylaxis:
washing hands before meals;
proper washing of vegetables eaten raw;
treatment of patients;
proper disposal of feces; health education.
Trichinella
spiralis

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
causes trichinosis.
Distribution worldwide, especially in eastern Europe and
west Africa.
Morphology:
1) The adults female worms are up to 3-4  0.6 mm; the adult
male worms are up to 1.5  0.04 mm;
2) the incysted larvae (1 mm) is enclosed in a fibrous cyst
wall.
Localisation: small intestine (adult worms) and striated
muscles (larvae).
Any mammal (rat, bear, fox) can be infected, but pigs are the
most important reservoirs of human disease.
Infective stage for humans: larva.
Mode of transmission: alimentary (eating raw or undercooked
meat, usually pork, containing larvae encysted in the
muscle).
Trichinella spiralis

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Clinical manifestation:
initially diarrhea, abdominal pain followed by 1-2
weeks later by fever, muscle pain,
periorbital edema, and eosinophilia.
Death, which is rare, is usually due to congestive
heart failure or respiratory paralysis.
Laboratory diagnosis: muscle biopsy reveals
larvae within striated muscle; serologic test (become
positive 3 weeks after infection).
Prophylaxis
by properly cooking pork and by feeding pigs only
cooked garbage;
pork inspection in slaughter houses using a
trichinoscope.
Ancylostoma duodenale and Necator
americanus (hookworms)





cause ancylostomiasis
(hookworm infection).
Morphology:
1) Adult worms about 1 cm in
length;
2) Eggs are translucent, oval with
blunt poles, 40-60 micro;m in
size;
3) the rhabditiform larva is about
0.25-0.5 micro;m with
rhabditiform oesophagus (1/3
body length), pointed tail end;
4) the filariform larva is about
0.6-0.7 micro;m with cylindrical
oesophagus (1/4 body length),
sharply pointed tail.
Hookworms

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
Hosts: humans.
Mode of transmission:
penetration of skin by filariform
larva
Infective stage: filariform
larva.
Clinical manifestation:
1) invasion stage (the larvae
penetrate the skin): dermatitis
and itching (“ground itch”);
2) migration stage: pneumonia
with eosinophilia;
3) intestinal stage: anemia,
diarrhea, abdominal pain,
nausea.
Hookworms


Laboratory diagnosis: eggs in the
stool; blood in the feces is frequent
finding.
Prophylaxis: disposing of sewage
properly and wearing shoes.
Thank you for
attention!