Liver Flukes

Diyala University
Collage of Medicine
Department of Microbiology
Practical Parasitology
3nd stage
Lab 13: Fascioliasis
Liver Flukes
Liver Flukes
Fasciola species
• Effects sheep, cattle, and sometimes humans
• Found in the liver and biliary passages of humans and ruminants
• Fasciola hepatica
– Sheep liver fluke, Temperate liver fluke
F. hepatica is distributed worldwide, and causes great economic losses in
sheep and cattle. It has been known as an important parasite of sheep and
cattle for hundreds of years.
• Fasciola gigantica
– Giant liver fluke
– Tropical liver fluke
•
Clonorchis sinensis
• Chinese liver fluke
• Oriental Liver Fluke
Liver Flukes
Fasciola species
• Mode of transmission is by ingestion of metacercariae found
in edible aquatic plants or by drinking water with floating
metacercariae
• Metacercariae excysts in the duodenum or jejunum and
liberate the juvenile fluke
• Juvenile fluke penetrates the intestinal wall and reaches the
liver capsule
• The parasite burrows into the liver parenchyma where it
grows and develops
• It becomes sexually mature in the bile ducts
• Definitive host:
– Sheep
– Cattle
– Humans (Accidental)
– Other Mammals
• First Intermediate Host:
– Fresh Water Snail
Lymnea philippinensis
• Second Intermediate Host
– Watercress
– Grass
• Geographic Range
– Cosmopolitan; anywhere sheep and cattle are
raised
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Fasciola hepatica
• Adult Worm
– 20-30mm long
– 8-15mm wide
– Large, broad, flat
body
– Anterior end forms
a prominent
cephalic cone
– Small oral and
ventral suckers
– Long and highly
branched intestinal
caeca
• Fasciola hepatica Ova
–
–
–
–
–
Large
Ovoid
Operculated
Bile stained
unsegmented
Eggs of fasciola hepatica, large, operculated, ovoid in shape
Life cycle of Fasciola hepatica
• The life cycle of Fasciola hepatica starts when
a female lays eggs in the liver of an infected
human. Immature eggs are discharged in the
biliary ducts and taken out in the feces. If
landed in water, the eggs become
embryonated and develop larvae called
miracidia. A miracidium invades an aquatic
snail and develops into cercaria, a larva that is
capable of swimming with its large tail.
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• The cercaria exits and finds aquatic vegetation where it
forms a cyst called Metacercariae. A human eats the raw
freshwater plant containing the cyst. The Metacercariae
excysts in the first part of the small intestine, duodenum. It
then penetrates the intestinal wall and gets into the
peritoneal cavity.
• It reach the liver and starts eating liver cells. This happens
only a few days after the initial contact with the parasite.
Usually the larva spends a few weeks just browsing and
eating the liver. Then it relocates to the bile duct where it
begins its final stage and becomes an adult. It takes about
three months for the Metacercariae to develop into an
adult. Adult females can produce up to 25000 eggs per day.
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Symptoms
• Acute
–
–
–
–
–
More common in sheep
10,000+ Metacercariae consumed at one time
Dramatic Liver Inflammation,
Frequently Resulting in Death
Asymptomatic
• Chronic
– More Common and Rarely Fatal
– Nonspecific Symptoms or Asymptomatic
• Halzoun
– Eating raw, infected liver
– Infects pharynx
– Causes swelling and obstructs breathing
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Symptoms
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•
•
•
•
•
•
•
•
•
•
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Abdominal Pain
Anemia
Hepatic Tenderness
Hepatomegaly resulting from Edema
Intermittent Fever
Jaundice
Lethargy
Nausea
Prolonged High Fever
Secondary Infections
Vomiting
Progress of Infection
• Ingestion
Metacercariae
• Ex-cyst in
Duodenum
• Burrows through
Intestinal Wall
• Enters Peritoneal
Cavity
• Migrates to Liver
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Pathology and liver damage
• Little damage is done by juveniles penetrating the
intestinal wall and the capsule surrounding the liver
but much necrosis results from migration of flukes
through the liver parenchyma Worms in bile ducts
cause inflammation and edema, which in turn
stimulate production of fibrous tissue in the walls of
these ducts. Thus thickened, the ducts can handle
less bile and are less responsive to needs of the liver.
Back pressure causes atrophy of liver parenchyma,
with concomitant cirrhosis and possibly jaundice. In
heavy infections the gall bladder is damaged, and
walls of the bile ducts are eroded complete.
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Epidemiology
• Infection begins when Metacercariae infected
aquatic vegetation is eaten or when water
containing Metacercariae is drunk. Humans
are often infected by eating watercress.
Human infections occur in parts of Europe,
northern Africa, Cuba, South America, and
other locales. It is one of the most important
disease agents of domestic stock throughout
the world and remaining so for years to come.
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Diagnosis
• Stool Samples
– Yellow-Brown Eggs
– Eggs Don’t Show for 4 Months
• Duodenal or Biliary Aspirate
• Antibody Test
– Can detect 2 Weeks After Infection
• Ultrasound
– Visualize Adults in Bile Duct
• CT Scan
- Reveals Burrows in Liver
• RFLP
– PCR restriction Fragment Length Polymorphism
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Fasciola gigantica
• Adult Worm
– Larger
– More lanceolate
– Less developed
shoulders (shorter
cephalic cone)
• Larger ventral sucker
• Fasciola gigantica Ova
– Larger but very similar to
Fasciola hepatica ova
- Because of similarities, it is
just safe to say Fasciola
ova
Liver Flukes
Fasciola hepatica and gigantica
Adult Worm •
Fasciola species
Treatment
• Bithionol
– 20-50 mg/kg body weight on alternate days to complete
10 to 5 doses
• Triclabendazole
– Also a recommended drug of choice due to:
• Efficacy
• Safety
• Ease of use
Liver Flukes
Clonorchis sinensis
• Adult Worm
– Narrow, oblong, flat
worm
– Oral sucker is slightly
larger than the ventral
sucker
– Blind intestinal caeca are
simple and extend to the
caudal region
– Life span is 20-30 years
Clonorchis sinensis Adult worm ( grey in colour, 12 – 20 X 3 – 5 mm )
Clonorchis sinensis
• Ova
– Bile stained
– Flask-shaped
– Operculated
– Does not hatch in
water but is ingested
with a molluscan host
– Has a terminal spine
– Electric bulb in shape
– Infective to snails
only
Clonorchis sinensis Egg, yellowish brown ( bile – stained )
small, flask – shaped and operculated possesses aterminal
hook – like spine.
Liver Flukes
Clonorchis sinensis
Life Cycle
Epidemiology
• Transmission is due to consumption of raw,
undercooked fish and salted and dried fish harboring
the metacercariae
• Over 30 million people are infected in Southeastern
Asia
• No reported cases in children below 10 years old
• Endemic in:
– China
– Japan
– Korea
– Vietnam
Pathogenesis and Clinical Manifestations
• Provokes intense proliferation of intestinal
epithelium
• Acute stage (less than 1 month of infection)
– Chills
– Fever
• Chronic stage
– Cirrhosis
– Portal hypertension
Diagnosis
• Detection of parasite egg in stool
• Clonorchis, Opistorchis and Hetrophyid ova
may not be differentiated under ordinary light
microscope
• ELISA with crude Clonorchis sinensis antigen
• Enzyme immunoassay (EIA
• Polymerase Chain Reactions
Treatment
• Praziquantel
– 25 mg/kg three times a day for two days
– 60 mg/kg in three doses for one day
– May be used together with albendazole for light
and moderate infections