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F.hepatica

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the Medical Parasitology of Fasciola hepatica if BioMedical Science

the Medical Parasitology of Fasciola hepatica if BioMedical Science

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  • FiFi Faridz BioMedical Science
  • Transcript

    • 1. TREMATODA Fasciola hepatica
    • 2. Introduction
      • Trematodes are flukes:
      • Class Trematoda;
      • Phylum Platyhelminthes.
      • Subclass: Digenea,
      • Order: Protostomata,
        • Suborder: Strigeata
          • genus Schistosoma
        • Suborder :Distomata
          • genus Fasciolopsis, Opisthorchis, Clonorchis, Paragonimus.
    • 3. Cont…
      • Some specific examples include:
        • Fasciola hepatica ( liver fluke)
        • Clonorchis sinensis (liver)
        • Fasciolopsis buski (intestinal)
        • Paragonimus westermani (lung)
        • Schistosoma spp. (blood).
    • 4. Fasciola hepatica
      • "sheep liver fluke," is misleading since this parasite is found in animals other than sheep (including cattle and humans),
      • resides in the bile ducts inside the liver.
      • adult reside in the intrahepatic bile ducts , produce eggs, and the eggs are passed in the host's feces.
      • Transmission
        • through the ingestion of raw, fresh-water vegetation on which the flukes in their metacercariae form are encysted.
        • The plants become exposed to the metacercariae when the body of water that the vegetation is growing in becomes contaminated by eggs in the fecal matter of an infected host.
        • Nearly all cases are a result of watercress consumption beside alfalfa and water lettuce.
    • 5. The Adult
      • one of the largest flukes in the world.
      • 20 -30mm in length and 13 mm in width
      • Leaf shape characteristic with the anterior end broader than the posterior end and an anterior cone-shaped projection.
      • Possesses a powerful oral sucker at the anterior cone and a ventral sucker at the base of the cone  attach to the lining of the biliary ducts.
      • monoecious - possesses ovaries and testes which are highly branched and allow for individual flukes to produce eggs independently.
    • 6. A stained adult Fasciola hepatica ; approximate length = 20 mm.  The internal organs are highly branched, thus making it very difficult to differentiate the various internal organs All of their major systems are branched, including the intestine, testes, and ovary.
    • 7.  
    • 8. The ova Length 130-145 µm Width 70-90 µm Regular ellipse Thin shell Operculum at one pole Granular yellowish-brown contents filling whole egg
    • 9. egg capsule with emerging miracidium of Fasciola hepatica .  400x unembryonated egg capsule of F. hepatica . earlier stage of development.  400x embryonated egg capsule of Fasciola hepatica.  So-named because the miracidium is fully formed and ready to emerge.  The operculum can be seen to the left.  400x
    • 10. Redia and cercaria of Fasciola hepatica Miracidium of Fasciola hepatica . This ciliated, non-feeding larval stage, has about 24 hours to find its specific snail host, such as Fossaria modicella or Stagnicola bulimoides.  400x
    • 11. The Life Cycle
    • 12. Cont..
      • Eggs passed in the feces develop into miracidia in ~2-4 wk, depending on temperature, and hatch in water.
      • Miracidia infect lymnaeid snails, in which development and multiplication occur through the stages of sporocysts  rediae (sometimes daughter rediae)  cercariae.
      • After ~2 mo (or longer if temperatures are low), cercariae emerge from snails and encyst on aquatic vegetation.
      • Encysted cercariae ( metacercariae ) may remain viable for many months unless they become desiccated.
    • 13. Cont..
      • After ingestion by the host, usually with herbage, young flukes are released in the duodenum, penetrate the intestinal wall, and enter the peritoneal cavity.
      • The young flukes penetrate the liver capsule and wander in the parenchyma for several weeks, growing and destroying tissue.
      • They enter the bile ducts, mature, and begin to produce eggs. The prepatent period is usually 2-3 mo, depending on the fluke burden.
      • Adult flukes may live in the bile ducts of sheep for years; most are shed from cattle within 5-6 mo. Prenatal infections have been reported in cattle.
    • 14.  
    • 15.  
    • 16. Pathogenecity & Symptoms
      • ~50% asymptomatic
      • disease may appear anywhere from a few days to several years after infection
      • Eosinophilia is present with all infections at all stages and can be used as a diagnostic factor in ectopic and early stage infections when eggs are not be present in the stool.
      • When symptoms do appear, they occur in the following patterns:
    • 17.
      • Acute Phase:
        • Rarely seen in humans and occurs only when a large number of metacercariae are ingested at once.
        • Fever, tender hepatomegaly , and abdominal pain are the most frequent symptoms of this stage of infection
        • vomiting, diarrhea, urticaria (hives), anemia, may be present.
        • Caused by the migration of the F. hepatica larvae throughout the liver parenchyma.
        • The larvae penetrate the liver capsule and begin to produce symptoms 4-7 days after ingestion.
        • Migration and acute phase continues for 6-8 weeks until the larvae mature and settle in the bile ducts.
    • 18. Cont..
      • Chronic Phase:
        • more common in human
        • include biliary cholic, abdominal pain, tender hepatomegaly , and jaundice.
        • In children, severe anemia - common result of infection
        • biliary obstruction and inflammation  caused by the presence of the large adult worms and their metabolic waste in the bile ducts.
        • Inflammation of the bile ducts  leads to fibrosis and a condition called " pipestem liver ", (white appearance of the biliary ducts after fibrosis).
        • The final outcome  portal cirrhosis and even death.
    • 19. Cont..
      • Halzoun : worm settles in the pharynx .
      • Occurs when an individual consumes infected raw liver  The young adult worms then attach themselves to the pharyngeal mucosa  causes considerable pain, edema, and bleeding that can interfere with respiration.
      • The adults can live in the biliary ducts, causing symptoms for up to 10 years.
      • Ectopic Infection: Ectopic infections through normal transmission are infrequent but can occur in the peritoneal cavity, intestinal wall, lungs, subcutaneous tissue, and very rarely in other locations.
    • 20. Laboratory diagnosis
      • The definitive and most widely used form of diagnosis is the directly observed presence of Fasciola hepatica eggs either in a stool sample, duodenal aspirate or biliary aspirate.
      • However, the flukes do not begin to produce eggs until roughly 4 months after infection.
      • Until this time and in the case of ectopic infections where eggs are not present in the stool, serological tests can be used, the FAST-ELISA being the most popular.
      • It has a sensitivity of 95% and can detect specific F. hepatic antibodies as early as 2 weeks after infection .
      • Ultrasound can be used to visualize the adult flukes in the bile ducts
      • CT scan may reveal the burrow tracts made by the worms and dilation of the bile ducts.
    • 21. Treatment
      • Fascioliasis has a 80-100% success rate - Bithionol & Triclabendazole, an antihelmintic agent.
      • Along with pharmaceutical therapy, surgery may be necessary in very extreme cases to clear the biliary tract.
    • 22. Prevention
      • The presence of a substantial reservoir - keep domestic animal herds separate from the growing sites of aquatic. This limits the risk of contaminating the vegetation and thus decreases both human infection and the animal reservoir
      • The presence of the intermediate host , the Lymanaea snails - application of molluscicides to decrease the population of Lymnaea snails.
      • The opportunity for water source contamination by human and non-human hosts
      • Dietary practices that include the consumption of raw, untreated aquatic vegetation.
    • 23. Next : Fasciolopsis buski

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