Cysticercosis - Taenia Solium

Diagnosis

Indications for Testing

• Requires high index of suspicion in nonendemic areas

Criteria for Diagnosis

• Proposed diagnostic criteria for human cysticercosis
  • Absolute criteria
    • Demonstration of cysticerci by histologic or microscopic examination of biopsy materials
    • Visualization of the parasite in the eye by funduscopy
    • Neuroradiologic demonstration of cystic lesions containing a characteristic scolex
  • Major criteria
    • Neuroradiologic lesions suggestive of neurocysticercosis
    • Demonstration of antibodies to cysticerci in serum by enzyme-linked immunoelectrotransfer blot
    • Resolution of intracranial cystic lesions spontaneously or after therapy with albendazole or praziquantel alone
  • Minor criteria
    • Lesions compatible with neurocysticercosis detected by neuroimaging studies
    • Clinical manifestations suggestive of neurocysticercosis
    • Demonstration of antibodies to cysticerci or cysticercal antigen in CSF by ELISA
    • Evidence of cysticercosis outside the CNS (eg, cigar-shaped soft-tissue calcifications)
  • Epidemiologic criteria
    • Residence in a cysticercosis-endemic area
    • Frequent travel to a cysticercosis-endemic area
    • Household contact with an individual infected with Taenia solium
  • Key for diagnostic interpretation
    • Confirmation
      • 1 absolute criteria
      • 2 major, 1 minor, and 1 epidemiologic criteria
    • Probable
      • 1 major and 2 minor
      • 1 major, 1 minor, and 1 epidemiologic
      • 3 minor and 1 epidemiologic

Laboratory Testing

• CDC cysticercosis resources for health professionals and diagnosis recommendations
• Testing for consensus criteria
  • CSF antibody by ELISA with confirmation by Western blot
  • Serology – limited diagnostic use as a single test
    • 65-98% sensitive; 67-100% specific; may be useful if used with imaging data

Imaging Studies

• Diagnosis is most often made by MRI or CT brain scans; addition of serologic screening by ELISA with confirmation by Western blot increases sensitivity of diagnosis of cysticercosis
  • CT scan – high sensitivity and specificity; lower for ventricular or cisternal forms
    • Single or multiple rounded lesions of low density with a small hyperdense mural nodule representing the scolex (starry night appearance)
  • MRI – more sensitive than CT; much more expensive

Differential Diagnosis

• Vasculitis
  • Behçet syndrome
  • Wegener granulomatoses
  • Polyarteritis nodosa
• Central nervous system tumor 
• Seizure disorders 
• Stroke
• Infection
  • Mycobacterium tuberculosis (TB)
  • Fungal agents
  • Toxoplasma gondii
  • Brain abscess
  • Nocardia spp
  • Encephalitis
  • Meningitis
• Connective tissue diseases 
  • Systemic lupus erythematosus
  • Sjögren syndrome
• Other
  • Sarcoidosis

Clinical Background

Cysticercosis is a parasitic infection caused by the pork tapeworm, Taenia solium.

Epidemiology

• Incidence
  • Endemic in Mexico, Central and South America
  • Etiological agent in 10% of new onset seizures
• Sex – M:F equal

Organism

• Humans can be definitive host (adult worm in intestine) or dead-end intermediate host (cysticercosis)
• Humans are incidental hosts by contact with contaminated water or undercooked pork
• Human disease depends on site of infection
  • Tapeworm in intestine
  • Larval forms in tissues

Clinical Presentation

• Initial infection often asymptomatic
  • Rapid onset dependent on number of cysts and body site affected
• Symptoms begin when cyst dies; depends on where the cysts are located
• Dying cyst releases antigenic material, triggering the host inflammatory response
  • Neurocysticercosis (cysts in the brain) associated with seizures, meningitis/encephalitis, and obstructive hydrocephalus
  • If cerebral vascular accident occurs – patient presents with elevated intracranial pressure, seizures, headache, nausea, or mental status changes
• Ocular cysts
  • Usually vitreous; can be subretinal
  • Blurry or disturbed vision, swelling or retinal detachment

Treatment

• Treatment usually necessary
  • CNS disease may require surgical treatment for hydrocephalus

Indications for Laboratory Testing

• Tests generally appear in the order most useful for common clinical situations
• Click on number for test-specific information in the ARUP Laboratory Test Directory