Ascaris lumbricoides (giant roundworm)

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Key Points

  • Ascaris lumbricoides
    • Characteristics
      • Also known as the giant roundworm
      • Type of nematode (roundworm) parasite
    • Transmission
      • Fecal-oral
        • Ingestion of eggs in contaminated food or water
          • Eggs are found in feces of infected pigs and people
    • Pathogenesis and Presentation: Ascariasis
      • After ingestion, eggs hatch in intestines
      • Larvae penetrate intestinal wall and migrate through lungs
        • Migration occurs by way of liver and heart
        • Early pneumonitis
          • 1-3 weeks after ingestion of eggs
          • Early pulmonary involvement is known as Loeffler syndrome
          • Fever, wheezing, and bloody sputum may be seen
          • Eosinophilia
            • Common to most parasitic infections
      • Larvae ascend trachea and are coughed and swallowed
      • Swallowed larvae mature in intestines and become large worms
        • 6-8 weeks after ingestion of eggs
        • GI obstruction
          • Large worms may obstruct the intestines or biliary tracts
            • May cause obstruction at ileocecal valve
          • Intestinal perforation is a feared complication
          • Presents with nausea/vomiting, abdominal pain
    • Diagnosis
      • Fecal eggs seen in Stool O&P
        • Knobby coated, oval eggs seen in feces under microscope
      • PCR is gaining traction but may be too expensive for routine use
    • Treatment
      • Bendazoles
        • Albendazole or Mebendazole are both first-line
      • Pyrantel pamoate
        • Second-line agent; preferred in pregnant women