Cards (18)

  • Helminths
    Worm-like parasites
  • Helminths
    • All are relatively large (> 1 mm long); some are very large (> 1 m long)
    • All have well-developed organ systems and most are active feeders
    • Worms are often long-lived
  • Clinically relevant helminth groups
    Separated according to their general external shape and the host organ they inhabit
  • There are both hermaphroditic and bisexual helminth species
  • Helminth classification
    Based on the external and internal morphology of egg, larval, and adult stages
  • Helminths are worldwide in distribution; infection is most common and most serious in poor countries
  • Helminth disease distribution
    Determined by climate, hygiene, diet, and exposure to vectors
  • Modes of helminth transmission
    • Ingestion of eggs or larvae
    • Penetration by larvae
    • Bite of vectors
    • Ingestion of stages in the meat of intermediate hosts
  • Many helminth infections are asymptomatic; pathologic manifestations depend on the size, activity, and metabolism of the worms
  • Flukes (Trematodes)

    • Adult flukes are leaf-shaped flatworms
    • Prominent oral and ventral suckers help maintain position in situ
    • Hermaphroditic except for blood flukes, which are bisexual
    • Life-cycle includes a snail intermediate host
  • Tapeworms (Cestodes)

    • Elongated, segmented, hermaphroditic flatworms that inhabit the intestinal lumen
    • Larval forms, which are cystic or solid, inhabit extraintestinal tissues
  • Roundworms (Nematodes)

    • Adult and larval roundworms are bisexual, cylindrical worms
    • They inhabit intestinal and extraintestinal sites (Loa loafilarial)
  • Roundworms (Nematodes)
    Ascaris lumbricoides That can cause Ascariasis
    Largest SI worm (Jejunum & Ileum)
    ➢ Children
    85% Asymptomatic
    Fever
    Abdominal pain
    Diarrhea
    ➢ Malnutrition
    ➢ Learning difficulties
    Tx: • - Albenzadole • - Mebendazole • - Pyrantel pamoate
  • Schistosomiasis
    A disease caused by flukes
  • Ascariasis
    A disease caused by roundworms / nematodes
  • Schistosomiasis
    • Snail fever / Bilharzia / Katayama fever
    • Itchy rash (swimmer’s itch)
    • Abdominal pain, dysentery, hematuria 🡪 liver & renal failure, bladder cancer
  • Important Cestodes
    Taenia saginata : Beef tapeworm
    Taenia solium : Pork tapeworm
    Echinococcus granulosus: Dog tape worm
    Taenia asiatica: Asian tapeworm
    (morphology close to T.saginata; life cycle similar to T.solium))
    Diphyllobothrium latum: Fish tape worm
    Hymenolepis nana: Dwarf tape worm
    • Mode of Transmission ( Cestodes )Ingestion of raw or under cooked Beef (T.saginata) or Pork (T.soilum) with encysted larval stagecysticercus