Echinococci and other tissue helminths

Echinococcus - Cysts of Despair

• Organism: Echinococcus granulosus (cystic), E. multilocularis (alveolar).
• Transmission: Ingestion of eggs from canid (dog, fox) feces. Humans are accidental intermediate hosts; sheep are common intermediates.
• Pathogenesis: Larvae form slow-growing hydatid cysts, primarily in the liver (~70%) and lungs.
  • E. granulosus cysts contain "hydatid sand" (protoscolices).
  • E. multilocularis is more invasive, mimicking malignancy.
• Clinical: Often asymptomatic for years. Presents with RUQ pain, mass effect, or hepatomegaly.

⭐ Spillage of cyst fluid, either spontaneously or during surgery, can cause life-threatening anaphylactic shock and disseminate the infection.

• Diagnosis:
  • Imaging (US/CT/MRI) is key, showing characteristic cysts, often with "egg-shell" calcification or daughter cysts.
  • Serology confirms exposure.
• Treatment: Albendazole, PAIR (Puncture, Aspiration, Injection, Re-aspiration), or surgery.

Taenia solium - Brain Invaders

• Organism: Pork tapeworm (cestode).
• Transmission & Disease:
  • Taeniasis (Intestinal): Ingesting larvae (cysticerci) in undercooked pork.
  • Cysticercosis (Tissue/Brain): Ingesting eggs from human feces (fecal-oral route).
• Neurocysticercosis (NCC) Presentation:
  • Seizures are the most common symptom.
  • Headaches, focal neurological deficits, signs of increased intracranial pressure.
• Diagnosis:
  • Neuroimaging: CT or MRI reveals cystic lesions. Brain parenchyma may show a "Swiss cheese" appearance.
  • Serology: Enzyme-linked immunoelectrotransfer blot (EITB) is highly specific.
• Management:
  • Antiparasitic therapy: Albendazole or Praziquantel.
  • Corticosteroids are co-administered to reduce inflammation from dying cysts.

⭐ Treatment with antiparasitic drugs can paradoxically worsen neurological symptoms due to an intense inflammatory reaction to dying cysticerci; this is why concurrent steroid administration is critical.

Other Tissue Worms - Migrating Menaces

• Toxocara canis/cati (Visceral/Ocular Larva Migrans)

  • Source: Ingestion of eggs from dog/cat feces.
  • Visceral (VLM): Fever, hepatomegaly, marked eosinophilia in young children.
  • Ocular (OLM): Unilateral vision loss, strabismus; mimics retinoblastoma.
  • Tx: Albendazole.

• Trichinella spiralis (Trichinosis)

  • Source: Undercooked pork, bear, or wild game.
  • Path: Larvae encyst in striated muscle.
  • Sx: GI upset → fever, myalgia, splinter hemorrhages, periorbital edema.
  • Labs: ↑ Eosinophils, ↑ Creatine Kinase (CK).

  ⭐ Classic Triad: Periorbital edema, myalgia, and eosinophilia.

• Baylisascaris procyonis (Raccoon Roundworm)

  • Source: Ingestion of eggs from raccoon feces.
  • Path: Aggressive, often fatal, neural larva migrans.

High‑Yield Points - ⚡ Biggest Takeaways

• Echinococcus granulosus (dog host) causes hydatid cysts; rupture risks anaphylaxis. Imaging shows eggshell calcification.
• Taenia solium eggs cause neurocysticercosis (seizures). Larvae in undercooked pork cause intestinal taeniasis.
• Trichinella spiralis (undercooked pork/bear) presents with myalgia, periorbital edema, and eosinophilia.
• Toxocara canis (dog/cat feces) causes visceral and ocular larva migrans in children.