NEMATODES

• Nematodes

  Multicellular parasites that appear round in cross section
• Nematode morphological forms

  • Eggs (female sex cells after fertilization)
  • Juvenile worms known as larvae
  • Adult worms
• Nematode eggs

  • Vary in size and shape
  • Develop into larvae in appropriate environment
• Nematode larvae


  • Typically long and slender
  • Complete maturation process to become adult worms
• Nematode adults

  • Sexes are separate
  • Adult females are usually larger than adult males
  • Have complete digestive and reproductive systems
• Nematode life cycle

  1. Eggs or larvae enter host

  2. Develop into adult worms in intestine

  3. Adult females lay eggs

  4. Eggs/larvae develop outside host and infect new host
• Some nematode life cycles involve tissue as the primary residence of the organisms
• Most nematodes have the ability to exist independent of a host (free-living)
• Juvenile stage of developing nematode worms

  Larvae
• Adult nematodes are recovered in clinical samples
• Factors affecting severity of nematode infection

  • Number of worms present
  • Length of time infection persists
  • Overall health of the host
• Nematode infections can last up to 12 months or longer, some up to 10-15 years or more
• Reinfections and autoinfections can increase infection time to several years and beyond, some persist indefinitely
• Nematode intestinal infection symptoms

  Abdominal pain, diarrhea, nausea, vomiting, fever, eosinophilia<|>Skin irritation, skin blisters, muscle involvement
• Unhealthy individuals with a heavy worm burden are prone to experiencing severe nematode infections
• Nematodes


  Belong to the phylum Nemathelminthes, considered a class
• Nematode groups

  • Intestinal species
  • Intestinal-tissue species
• Enterobius vermicularis (pinworm)


  Eggs are oval, flattened on one side, with a thick colorless shell and developing larva<|>Adult females are 7-14mm long, yellowish-white with a pointed tail
• Enterobius vermicularis egg recovery


  Cellophane tape prep from perianal region is specimen of choice
• Enterobius vermicularis is the most common helminth infection in the US, especially in white children
• Enterobius vermicularis infection symptoms

  Intense itching and inflammation of anal/vaginal areas, intestinal irritation, nausea, vomiting, irritability, difficulty sleeping
• Total eradication of pinworm is highly unlikely due to ease of transmission
• Albendazole, mebendazole or pyrantel pamoate are treatments of choice for Enterobius vermicularis
• Eggs and adult females are the morphological forms recovered in pinworm infection