Trematodes

• Trematodes


  2 main sub-classes: Monogenea (direct lifecycle), Digenea (indirect lifecycle)
• Digenea Family


  • Fasciolidae
• Fasciola hepatica


  Liver fluke, affects sheep and cattle in UK, also zoonotic
• Fasciola hepatica


  • Large flattened leaf shape
  • Blind alimentary tract
  • Hermaphrodite - cross and self fertilisation
  • Adult fluke in bile ducts, gall bladder - blockages, malnutrition
  • Juvenile fluke in liver - scours, jaundice
• Lifecycle of Fasciola hepatica

  1. Eggs passed in faeces

  2. Miracidium hatches, finds snail host

  3. Sporocyst, redia, cercariae develop in snail

  4. Cercariae encyst as metacercariae on vegetation

  5. Metacercariae ingested by definitive host

  6. Juvenile fluke penetrates intestine, migrates to liver
• Fasciola hepatica lifecycle takes 5 months, prepatent period is 3 months
• Epidemiology of Fasciola hepatica

  • Availability of snail host, damp muddy fields, poorly drained
  • Miracidia from overwintered eggs or laid in spring/early summer
  • Snails infected in summer, autumn
• Control of Fasciola hepatica

  1. Remove moisture and snails

  2. Move animals to clean well drained ground

  3. Reduce snail population with molluscicide

  4. Treat animals with triclabendazole every 3-4 weeks
• Pathogenicity of Fasciola hepatica

  • Acute - ingestion of large numbers, liver failure, death
  • Sub-acute - fewer numbers, jaundice, bottle jaw
  • Chronic - gradual increase, long term exposure harder to pick up