This document discusses several species of hermaphroditic flukes that can infect humans, including Fasciola hepatica (sheep liver fluke), Clonorchis sinensis, and Opisthorchis species. F. hepatica lives in the liver and bile passages of sheep and can also infect humans. It has a complex life cycle involving snail intermediate hosts. Infection causes liver damage and inflammation. Symptoms include abdominal pain and eosinophilia. Diagnosis is via stool or bile examination or serology. Treatment is with triclabendazole. Prevention involves proper handling and cooking of water plants and controlling snail populations.

1. HERMAPHRODITIC FLUKES
LIVER FLUKES
Dr Mudenda J

2. • Adult hermaphroditic flukes infecting humans live in the biliary,
intestinal or respiratory tracts.
• These locations are ideal for evading host defense mechanisms & also
facilitates spread of eggs to the environment.
• Flukes found in human biliary tract are Fasciola hepatica, Clonorchis
sinensis & less often Opisthorchis species.

3. Fasciola Hepatica
• Also known as Sheep liver fluke.
• Its primary host is sheep & cattle to a lesser extent.
• It is the largest & most common liver fluke found in humans.
• Has a worldwide distribution & mainly found in sheep-rearing areas.
• Causes ‘liver rot’ disease in sheep.

4. Fasciola hepatica, the sheep liver fluke Fasciolopsis buski

5. Habitat
• Is the liver & biliary passages of the definitive host.
Morphology
• Large leaf-shaped fleshy fluke, 30 mm by 15 mm grey or brown in
color.
• Has a life span of about 5 years in sheep & 10 years in humans.

6. Egg
• Large, ovoid, operculated & bile-stained.
• Contain an immature larva, the miracidium.
• Eggs are unembryonated when freshly passed.
• Eggs are laid in the biliary passages & are shed in feces.
• Eggs of F. hepatica & Fasciolopsis are similar.

8. Life Cycle
• Passes its life cycle in 1 definitive host & 2 intermediate hosts.
• Definitive host: Sheep, goat, cattle & man.
• Intermediate host: Snails of the genus Lymnaea & Succinea.
• Encystment occurs on aquatic plants, which act as 2nd intermediate
host.
• Mode of infection: Ingestion of metacerceriae encysted on aquatic
vegetation.

9. • Eggs contain an immature larva(embryo), the miracidium.
• The embryo matures in water in about 10 days & the miracidium
escapes.
• It penetrates the tissues of first intermediate host, snails of the genus
Lymnaea .
• In snail, the miracidium progresses thru the sporocyst and the 1st & 2nd
generation redia stages to become the cercariae in abt 1–2 months.
• Cercariae escape into water & encyst on aquatic plants or blades of
grass to become metacercariae(can survive for long periods).

10. • Metacercariae excyst in the duodenum of the definitive host & pierce
the gut wall to enter the peritoneal cavity.
• They penetrate the Glisson’s capsule, traverse the liver parenchyma &
reach the biliary passages, where they mature into the adult worms in
about 3–4 months.

12. Pathogenicity
• F. hepatica causes zoonotic disease fascioliasis.
• Fascioliasis differs from clonorchiasis in that F. hepatica is larger & so
causes more mechanical damage.
• In traversing the liver tissue, it causes parenchymal injury & severe
inflammatory response.
• Some larvae penetrate right thru the liver & diaphragm ending up in
the lung.
• After ingestion of metacercariae is followed by a symptom-less
incubation period starts lasting few days to a few months.

13. Pathogenicity
• The disease has the following phases
1. Asymptomatic phase
• Fever,RUQ abdominal pain & hyper eosinophilia may occur.
2. Acute or invasive phase
• During the migration of the larva, pts present with fever, RUQ pain,
eosinophilia & tender hepatomegaly.
• The symptoms subside as parasites reach their final destination.

14. 3. In chronic or latent phase
• The parasite has reached the bile ducts
• Stimulates inflammation in the biliary epithelium leading to fibrosis
• Pts may develop biliary obstruction, biliary cirrhosis, obstructive
jaundice, cholelithiasis & anemia.
• Bacterial super-infections may also occur.
• No association to hepatic malignancy has been ascribed to fascioliasis.

15. • Occasionally, ingestion of raw liver of infected sheep results in a
condition called halzoun (meaning suffocation).
• The adult worms in the liver attach to the pharyngeal mucosa, causing
edematous congestion of the pharynx & surrounding areas,
• This leads to dyspnea, acute dysphagia, deafness, and rarely,
asphyxiation.
• Halzoun is particularly common in Lebanon & other parts of the
Middle East & North Africa.

16. Diagnosis
• Specimens: Stool, duodenal or biliary aspirates & blood
1. Stool Microscopy
• Demonstration of eggs in feces or aspirated bile from duodenum is the
best method of diagnosis.
2. Blood Picture :It reveals eosinophilia
3. Serodiagnosis
• Serological tests such as ELISA, immunoelectrophoresis &
complement fixation for detection of specific antibody.
• In chronic fascioliasis, Fasciola copro-antigen may be detected in
stool.

17. 4. Imaging
• USG, CT scan, Endoscopic Retrograde Choangiopancreatography
(ERCP) and percutaneous cholangiography may be helpful in
diagnosis.
Treatment
• The drug of choice for the txt is Oral triclabendazole (10 mg/kg once),
a benzimidazole compound active against immature & adult parasites.
• Other drugs: bithionol (30–50 mg for 10–15 days) .
• Prednisolone at a dose of 10–20 mg/kg is used to control toxemia.

18. • Note-Praziquantel which is active against most trematodes (flukes),is
not active against Fasciola, therefore not recommended.
• In patients with biliary tract obstruction, manual extraction of adult
flukes e.g., via endoscopic retrograde cholangiopancreatography
(ERCP) may be indicated.

19. Fasciola gigantica
• Also called the giant liver fluke.
• It’s a parasite of herbivorous animals although human cases have also
been reported.
• The life cycle, pathogenicity & clinical features are similar to those
of Fasciola hepatica but intermediate hosts are different snails.
• It is larger than F. hepatica & lives in the biliary passage of its host.
• Its egg is hard to make difference from F. hepatica & F. buski.
• They are a worldwide distribution & economic importance in
livestock raising.

20. Prevention of Fasciola
• Prevention can be achieved by using the following steps-
• Inspecting the plants, especially watercress for metacercariae or not
eating plants grown in areas where herbivorous mammals are found.
• Prevent contamination of water with feces from infected animals or
people in areas where aquatic plants are used for food.
• Cook water-grown vegetables thoroughly before eating.

21. • Water-grown vegetables should be washed with 6% vinegar or
potassium permanganate( KMnO4) for 5-10 minutes, which kills the
encysted metacercariae( more successful than attempts to halt the
consumption of raw vegetables).
• Avoid sewage contamination of growing areas.
• The use of molluscicides is the most frequent public health
intervention, as it prevents the transmission of many other trematodes,
including Schistosoma species.
• Health education