FASCIOLA HEPATICABy- Yewande Ayodele. (from Nigeria, 2nd year group 2, January 2008)

What is Fasciola hepatica??? Fasciola hepatica, also known as the

common liver fluke or sheep liver fluke, is a parasitic flatworm of the class Trematoda, phylum Platyhelminthes that affects the liver of various mammals, including man. The disease caused by the fluke is known as fascioliasis.

This parasite presents a large size: 20-30 x 8-13 mm; on encephalic zone exists: oral and ventral suckers;

Fluke infections are diseases of the digestive tract and other organ systems caused by parasitic flatworms (Trematodes) that involve hosts other than human beings.

The immediate host of F. hepatica is a snail such as Limnea truncatula , in which the parasite can reproduce asexually.

The ova are oval, yellowish, operculated; inhabit human bile ducts and gallbladder.

Life Cycle

Immature eggs are discharged into the biliary ducts and in the stool(1) . Eggs become embryonated in water(2) , eggs release miracidia(3) ,which invade a suitable snail intermediate host(4) , including many species of the genus Lymnae . In the snail the parasites undergo several developmental stages (sporocysts(4a) ,rediae(4b) ,and cercariae(4c) ). The cercariae are released from the snail(5) and encyst as metacercariae. Humans can become infested by ingesting metacercariae-containing fresh water plants,

especially watercress(6) .After ingestion, the metacercariae excyst in the duodenum(7) and migrate through the intestinal wall, the peritoneal cavity, and the liver parenchyma into the biliary ducts, where they develop into adults(8) .In humans, maturation from metacercariae into adult flukes takes approx. 3-4 months. The adult flukes reside in the large biliary ducts of the mammalian host. Fasciola hepatica infect various animal species, mostly herbivores

Pathogenicity

It induces local traumatic and toxic effects A serious consequence of the liver damage

caused by fascioliasis is that latent Clostridium novyi spores can be activated by the low oxygen conditions in the damaged tracts the parasite forms in the liver – this can lead to “black disease” , caused by Clostridium novyi type B or immune- mediated haemolytic anemia (IMHA) leading to hemoglobinuria caused by Clostridium novyi type D.

Slide , showing it’s internal organs

Diagram of the adult worm-

Diagnosis

Diagnosis of fluke infections is based on the patient’s history and identification of the fluke’s eggs or adult form.

Stool specimens or body fluids samples may be sent to a laboratory for identification of the ova. I n some cases, adult flukes are found in the patient’s stools, vomit, sputum, or skin lumps(for lung flukes). In lung flukes, it is important to rule out tuberculosis through a tuberculosis skin test and a chest x-ray

Blood tests may also be useful in diagnosing fluke infections. In some cases, computed topography scans (CT scans) or ultrasound scans of the patient’s chest or brain (for lung flukes) or abdomen (for liver flukes) ,are useful.

Symptoms

During the acute phase (caused by migration of the immature fluke through the hepatic parenchyma), manifestations include abdominal pain, hepatomegaly, fever, vomiting, diarrhea, urticaria and eosinophilia, and can last for months.

In the chronic phase (cause by adult the fluke within the bile ducts), the symptoms are more discrete and reflect intermittent biliary obstruction and

and inflammation. Occasionally, ectopic locations of

infection (such as intestinal wall, lungs, subcutaneous tissue, and pharyngeal mucosa) can occur.

Treatment

Fluke infections are treated with antibiotic medication such as triclabendazole, praziquantel, bithionol, albendazole and mebendazole .

The main drug of choice is triclabendazole. This drug works by preventing the polymerisation of the molecule of tubulin into the cytoskeletal structures, microtubules.

However, resistance of F. hepatica has already been recorded in some parts of Australia and Ireland.

Treatment varies from several days to several weeks.

Cure rates range from 50-95%. Most patients experience mild side effects from these drugs. The prognosis for recovery from liver fluke infection is good, although patients with serious infections may be more vulnerable to other diseases. Most patients with lung fluke infections also recover, however, severe infections of the brain can cause death.

There are no vaccines against fluke infections.

Geographic Distribution

Fascioliasis occurs worldwide. Human infections with F. hepatica are found in areas where sheep and cattle are raised, and where humans consume raw watercress, including Europe, Middle East, and Asia. Infections with F. gigantica have been reported, more rarely in Asia, Africa, and Hawaii.

Prevention

Prevention includes: Boiling or Purifying drinking water,

Avoiding raw or undercooked fish or salads made from fresh aquatic plants,

Thoroughly cooking all food eaten in areas with fluke infestations

And controlling or killing the snails that are the flukes’ intermediate hosts.

Thanks for your attention…