SUBCLASS DIGENEA

• • Endoparasites
  • 2 or more hosts with at least 2 infective stages
  • Gastropod molluscs
  • Arthopod fish
  • Dorsoventrally flattened
  • Ventral sucker
• LIFE STAGES

  • Egg
  • brought out through feces, urine, sputum, and deposited in land
  • ingested by snails
• LIFE STAGES

  • Miracidium
  • Ciliated
  • Swimming larva
  • Penetrates body wall of a snail
• LIFE STAGES

  • Spoporocyst
  • saclike
  • gutless
  • has several embryo/germ cells
  • the embryo develops into another sporocyst or:
  • Redia
  • has mouth, pharnx, gut plus embryos
  • travels to gonads/digestive tracts
• LIFE STAGES

  • Cercaria
  • has digestive tract, suckers and tails
  • leaves the snail host to search for a 2nd intermediate host (encyst)
• LIFE STAGES

  • Metacercaria
  • Encysted larvae
  • has tissues of 2nd IH
  • excyst and migrate to their characteristic location and mature
• Clonorchis sinensis

  
• Clonorchis sinensis

  1. Embryonated eggs passed in feces
  2. Eggs ingested by snails
  3. Cercariae encyst in the skin/flesh of fish
  4. Metacercariae in fish gets ingested by human
  5. Excyst in the duodenum
  6. Adults in the biliary duct

  
• FASCIOLA HEPATICA

  1. Unembroynated eggs passed in feces
  2. Embryonated eggs in water
  3. Miracidia penetrates the snail
  4. Snail
  5. Sporocysts
  6. Rediae
  7. Cercariae
  8. Cercariae encysts on water plants
  9. Metacercariae ingested by human, sheep, or cattle
  10. Excyst in duodenum
  11. Adults in hepatic biliary ducts

  
• Disease caused by Fasciola Hepatica: LIVER ROT

  • Necrosis
  • Anemia
  • Pipestem fibrosis of the bile ducts
  • Cirrhosis of the liver
  • Jaundice
  • Gallbladder damage
• Disease caused by Fasciola Hepatica: HALZOUN

  • Bucco pharyngeal infection

  
• SCHISTOSOMA JAPONICUM

  1. In feces or in urine
  2. Eggs hatch and releases miracidium
  3. Miracidia penetrates snail tissue
  4. Sporocysts in snail
  5. Cercariae released by snail into water
  6. Cercariae tail detaches and becomes schistosomulae
  7. CirculationMigrates to liver and becomes adults
  8. Paired adults migrate to mesenteric venules of bowls/rectum

  
• DICROCOELIUM DENDRITICUM

  1. embryonated eggs in feces
  2. Eggs ingested by IH snails
  3. Cercariae is released via respiratory pore
  4. This gets eaten by ants, then cercariae encyst to metacercariae
  5. Definitive host eats infected ant
  6. Adult in bile duct

  (there are also incidental human infections)

  
• PARAGONIMUS WESTERMANI

  • Reduces human productivity and quality of life
  • Infection
  • Hosts are snails and crabs
• PARAGONIMUS WESTERMANI

  1. Unembryonated eggs
  2. Embryonated eggs
  3. Miracidia hatch and penetrates snail
  4. Sporocysts to Rediae to Cercariae
  5. Cercariae invade the crustacean and encyst into metacercariae
  6. Excyst in the duodenum
  7. Adults in cystic cavities in lungs

  
• PARAGONIMUS WESTERMANI

  Signs and Symptoms

  • Coughs of long duartion
  • Hemoptysis
  • Chest/back pain
  • No response to anti-TB medications

  Diagnosis: Sputum examination; Spinal tap

  Treatment: Praziquantel