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TREMATODES
-2Fasciola hepatica
Dicrocoelium dendriticum
Clonorchis spp
Paragonimus spp
Doç.Dr.Hrisi BAHAR
Fasciola hepatica
F. hepatica is a flattened,
leaf-shaped parasite about
2–5 cm long and at most
1 cm wide.
Dicrocoelium dendriticum
The lancet liver fluke
(0.5–1.0 ! 0.2 cm)
Fasciola hepatica and F. gigantica are bile duct parasites of
domestic ruminants.In their life cycle freshwater snails act as
intermediate host Humans become accidentally infected when they eat
plants to which infectious parasite stages (metacercariae) adhere
Dicrocoelium dendriticum is a bile duct parasite in sheep,
cattle, and other herbivores, Its life cycle includes two intermediate
hosts (terrestrial snails and ants). Humans become infected accidentally
when they ingest ants containing infective metacercariae of the lancet
liver fluke.
Fasciola hepatica egg
Dicrocoelium dendriticum egg
Life cycle of Fasciola hepatica
Adult liver flukes parasitize in the bile ducts.
They produce large golden brown,
operculated eggs that are shed by the bile
duct-intestinal tract route. Under favorable
conditions, a ciliate larva, the miracidium,
develops in the egg within a few weeks.
The miracidia then hatch and penetrate
into freshwater snails where they transform
into sporocysts.
Life cycle of Fasciola hepatica
After formation of further asexual reproductive
stages, tailed cercariae develop and swarm out
of the snails into the open water.
They soon attach to plants and encyst, transform
into infective metacercariae, which are then
ingested with vegetable food of their definitive
hosts.
Eating watercress contaminated with metacercariae
is one of the sources of infection for humans.
Life cycle of Fasciola hepatica
The juvenile liver flukes hatch from the cyst in the
small intestine, penetrate the intestinal wall, and
migrate through the peritoneal cavity to the liver.
After migrating through the hepatic parenchyma
for about six to seven weeks, the parasites finally
reach the bile ducts, in which they develop
to sexual maturity.
Egg excretion begins two to three months
Life cycle of Dicrocoelium dendriticum
It stands apart from most trematodes since it has a land
based life cycle. The definitive host's feces contain
miracidia which do not hatch until after they are eaten by
the first intermediate host, a land snail,
The miracidium emerges inside the intestine of the snail
and metamorphoses into a sporocyst and than into
cercaria.
The second intermediate host is the common brown ant,
There cercaria turns to metacercaria.
Upon ingestion by the definitive host, the metacercaria
arrive in the duodenum and migrate up the common bile
duct to the liver. The adult fluke matures in 6-7 weeks,
producing egg capsules about a month later.
Fasciola hepatica
Eating watercress contaminated with metacercariae is
one of the sources of infection for humans.
Dicrocoelium dendriticum
Humans become infected accidentally when they ingest
ants containing infective metacercariae of the lancet liver
fluke.
Such infections are rare and either run an asymptomatic
course or manifest in mild abdominal and hepatic
symptoms.
• Fasiola hepatica in liver
Fasiola hepatica in liver
Diagnosis of Fasciola infection . The manifestations to be
expected during the migration phase of the liver fluke include
mainly leukocytosis, eosinophilia, and a rise in liverspecific
serum enzymes. Detection of eggs in stool or duodenal
fluid is not possible until at least two to three months . Other
diagnostic tools include detection of serum antibodies and of
coproantigen in stool.
Diagnosis of Dicrocoelium infection. Diagnosis is based
on detection of eggs in stool (about 40 25 µm, oval, dark
brown containing a miracidium with two rounded germinal
cells) Ingestion of contamined beef or mutton liver can
result in egg excretion in stool without infection.This is
intestinal passage.
Treatment of Fasciola infection
The drug of choice is triclabendazole, the
infection can be avoided by not eating raw
watercress and other plants that may be
contaminated with metacercariae.
Treatment of Dicrocoelium infection
Praziquantel has been shown to be effective
against Dicrocoelium in animals .
Clonorchis spp
Liver flukes of the genera Clonorchis occur mainly in
river and lake regions of Asia and Eastern Europe.
The definitive hosts of Clonorchis species are fish
eating mammals like cats,dogs, pigs, and humans,in
which these trematodes colonize the bile ducts.
Clonorchis spp
The life cycle of these organisms involves various
species of aquatic snails as the first intermediate
hosts and freshwaterfish species as the second
intermediate hosts.
The infective metacercariae are localized in the
musculature of the fish and,when raw fish is
ingested, enter the intestinal tract of the definitive
host, they migrate through the common bile duct
Clonorchis spp egg
Clonorchis spp
Pathogenesis and clinical manifestations.
Clonorchis infections cause proliferations of the bile duct epithelium,
cystlike dilatation, inflammation,and fibrosis of the bile duct walls as
well as connective tissue proliferation in the hepatic parenchyma.
A high incidence of bile duct carcinomas has been reported from areas
in which C. sinensis are endemic.
Clinical symptoms of more severe infections include variable fever,
hepatocholangitic symptoms with hepatomegaly, leukocytosis, upper
pains, and diarrhea.
Clonorchis spp
Diagnosis, therapy, and prevention
Diagnosis is made by detection of eggs (26–32 lm long) in
stool or duodenal fluid
Therapy and prevention
The drug of choice is praziquantel; albendazole can also be
used.
Reliable preventive measures include boiling or frying fish
to kill the metacercariae, which die at temperatures as
lowas 70 C, and freezing to –10 8C for five days.
Paragonimus sp (Lung Flukes)
Lung flukes of the genus Paragonimus are endemic in
parts of Asia, Africa, and America.
Parasitize in pulmonary cysts and cause a
tuberculosis-like clinical picture.
Following development in two intermediate
hosts(freshwater snailsband crabs or crayfish),
infective stages (metacercariae) can be transmitted to
humans by eating the crabs or crayfish uncooked.
Parasite eggs are detectable in sputum or stool.
Paragonimus sp (Lung Flukes)
The sexually mature parasites live in cystlike
dilatations in the lungs,usually in connection
with the bronchial tree.
The yellow-brown, operculated eggs laid by
the adultworms are shed either in sputum or
stool.
Paragonimus sp.adult and egg
• egg
egg
Adult
Paragonimus sp (Lung Flukes)
The life cycle then continues in water,
where a miracidium develops in each egg,
hatches and invades an intermediatebhost.
Egg-shaped cercariae with short tails develop
in the first intermediate host, a freshwater
snail.
The cercariae encyst in the second intermediate
host like crayfish or crabs to form the infective
Metacercariae.
Paragonimus sp
When a suitable definitive host ingests the
crustaceans uncooked, the young trematodes
hatch in the small intestine,migrate through the
peritoneal cavity to the diaphragm and finally into
the lungs.
The prepatent period is two to three months.
Parasites that deviate from the normal migration
route may enter other organs.
Paragonimus sp
Besides humans, crustacean eating mammals play
a significant epidemiological role as reservoir
hosts.
Young lung flukes can be localized in the
musculature of pigs and other “transport hosts” and
be transmitted to humans who ingest the raw meat
of these animals.
Paragonimus sp
Clinical manifestations. Typical cases are
clinically characterized by pulmonary symptoms
chronic cough, bloody expectoration, thoracic pain.
Parasites following the normal or deviant migration
routes can also cause abdominal,hepatic,
pancreatic or CNS symptoms, or skin lesions like
swelling, nodules.
Paragonimus sp
Diagnosis, therapy, and prevention.
An etiological diagnosis is based on detection of eggs in
sputum or stool and of serum antibodies.
Regarding the differential diagnosis especially tuberculosis
must be kept in mind.
The drug of choice is praziquantel, but triclabendazolem
can also be used .
Cooking crustaceans before eating them is a reliable
preventive measure.