Helminth

Cysticercosis

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Cysticercosis, Neurocysticercosis, Pork Tapeworm, Tenia Solium Infection, Taenia solium, Taeniasis

  • Epidemiology
  1. Immigrants from Central America and South America comprise the greatest number of cases in the U.S.
  2. U.S. natives comprise 15% of Cysticercosis-related deaths
  3. Most common cause of acquired Epilepsy in the developing world
  • Pathophysiology
  • Tapeworm lifecycle and pathogenesis
  1. Pork Tapeworm infection (Taenia solium)
  2. Infection originates in pigs as Tapeworm larvae (cysts)
  3. Key points related to Cysticercosis pathogenesis
    1. Tapeworms cycle between human hosts and pigs
      1. Humans ingest Tapeworm cysts in undercooked pork
      2. Pigs ingest human feces with Tapeworm eggs
    2. Ingestion of cysts does not cause Cysticercosis
      1. Cyst ingestion allows Tapeworm development
      2. Ingested eggs are required for Cysticercosis
    3. Cysticercosis is a result of fecal-oral ingestion
      1. Cysticercosis is not due to eating undercooked pork
      2. Cysticercosis occurs from infected human feces
        1. Can infect vegetarians from unwashed fruit
  4. Humans ingest Tapeworm larvae with undercooked pork
    1. Larvae attach to human gut (via scolex, a hook-like head) and grow to adult Tapeworm
    2. Adult Tapeworm sheds egg bundles (proglottids)
    3. Proglottids passed into human stool
  5. Pigs ingest food contaminated with infected human stool
    1. Pigs ingest Tapeworm eggs (oncospheres)
    2. Eggs develop into Tapeworm larvae
    3. Larvae enter pig bloodstream
    4. Larvae invade pig tissues and develop into cysts
  6. Humans ingest food contaminated with infected stool
    1. Source: Ingested Tapeworm eggs
      1. Infected food handlers who do not wash hands
      2. Household contacts with Taenia solium infection increases transmission risk
      3. Fruit or vegetables with infected fertilizer
    2. Source: Autoinoculation
      1. Tapeworm eggs retrograde travel gut to Stomache
    3. Cysticercosis occurs in similar fashion as with pigs
      1. Ingested eggs develop into Tapeworm larvae
      2. Larvae travel via blood to tissue where they embed
      3. Larvae form cysts in brain, eyes, spine, and muscle
  • Signs
  1. General
    1. Cysts (cysticerci) may be single or multiple (even hundreds)
    2. Cysts are initially asymptomatic for years
      1. Larvae in cysts are walled off from host response
    3. Cysts degenerate and cause severe inflammation
      1. Dying Parasites as well as larval release causes host antigenic response
      2. Inflammation and edema (and in some cases, mass effect) result in symptoms
  2. Distribution
    1. Brain Parenchymal Neurocysticercosis (90% of cases)
      1. Seizures (most common, occuring in 50-80% of symptomatic patients)
        1. Del Brutto (1992) Neurology 42(2): 389-92 [PubMed]
      2. Headache
      3. Parkinsonism
      4. Encephalopathy (if numerous brain cysts)
      5. Obstructive Hydrocephalus (if ventricles involved, occurs in 20-30% of symptomatic patients)
        1. Papilledema may be seen in up to 28% of patients
      6. Chronic Meningitis (mass effect with large cysts)
      7. Cranial Nerve palsy (mass effect with large cysts)
      8. Radiculopathy (if spinal cord involved - uncommon)
      9. Garcia (2005) Lancet Neurol 4(10): 653-61 [PubMed]
    2. Skeletal muscle lesions
      1. Typically asymptomatic
    3. Subcutaneous lesions
      1. Typically asymptomatic
    4. Eye lesions (1-3% of cases)
      1. Ocular lesions (e.g. vitreous lesions)
      2. Extraocular muscle lesions
      3. Proptosis
      4. Visual disturbance or Vision Loss
  • Imaging
  • Head
  1. MRI Brain is preferred (otherwise CT Head if MRI is not available)
  2. Diagnostic findings suggestive of Neurocysticercosis
    1. Single <2 cm lesion
    2. No midline shift
    3. Larval sucking parts (scolex) may be visible (pathognomonic)
  3. Differentiating cyst stage
    1. Viable non-degenerating cyst: Not contrast enhanced
    2. Degenerating cyst (symptomatic): Contrast-enhancing
    3. Old cysts: Calcified
  4. Differential diagnosis
    1. Tuberculosis
    2. Parasitic Brain Lesions (e.g. Toxoplasmosis)
    3. Brain Tumor
    4. Brain Abscess
  5. Other imaging modalities
    1. Consider MRI brain if CT Head non-diagnostic
    2. Ultrasound or CT are approriate to image eye
  • Labs
  1. Cysticercal Antibody: Serum Enzyme-linked immunoblot assay (EITB)
    1. Test Sensitivity: >65%
    2. Test Specificity: >67%
    3. Serum more accurate than CSF titers
    4. Indicated if imaging is non-diagnostic
  2. Biopsy of infected tissue
  3. Lumbar Puncture (contraindicated if CNS mass effect)
    1. Obtain head imaging first to exclude CNS mass effect
    2. Exclude other CNS diagnoses
  • Diagnostics
  1. Dilated Eye Exam (fundoscopic exam)
    1. Indicated before initiating therapy in patients with ocular or neurologic symptoms
  • Management
  1. Precautions: Do not start treatment without Consultation
    1. Treatment is individualized by multiple factors
    2. Antiparasitic agents are not uniformly indicated
      1. Overwhelming host response could be devastating
      2. Use may risk morbidity or mortality in some cases
      3. Albendazole with Systemic Corticosteroids is typically used
    3. Consult infectious disease in nearly all cases
    4. Consult neurology and neurosurgery in CNS cases
  2. Skeletal muscle lesions
    1. No treatment unless painful
    2. Consider surgical excision
  3. Eye: Intraocular lesions
    1. Consult ophthalmology
    2. Surgical excision for intraocular lesions
  4. Eye: Extraocular muscle lesions
    1. Consult ophthalmology
    2. Surgical excision for intraocular lesions or
      1. Consider Albendazole with Corticosteroid
  5. Brain: Subarachnoid and intraventricular lesions
    1. Ventricular shunt placed if Hydrocephalus
    2. Surgical excision for most lesions or
      1. Consider Albendazole with Corticosteroid
  6. Brain: Parenchymal Neurocysticercosis
    1. Albendazole with Dexamethasone (preferred)
      1. Do not use in massive infection
      2. Not needed in calcified lesions
  7. Brain: Seizures
    1. See Status Epilepticus for acute Seizure management
    2. Seizure Prophylaxis continued for 6-12 months after radiographic resolution of lesions
      1. Phenytoin
      2. Carbamazepine
      3. Levetiracetam
      4. Topiramate
  • Prognosis
  1. Brain Parenchymal disease with few cysts has better outcome than extraparenchymal involvement or numerous cysts
  • Prevention
  1. See Prevention of Foodborne Illness
  2. Careful and frequent Hand Washing
  3. Wash raw fruits and vegetables before ingesting
  • Resources