Cysticercosis - Taenia Solium

Diagnosis

Indications for Testing

• Seizures or hydrocephalus not caused by common etiologies
• Calcitic cysts on CT scan

Criteria for Diagnosis

• 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 cerebrospinal fluid (CSF) by ELISA
  • Evidence of cysticercosis outside the central nervous system (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
    • One absolute criterion
    • Two major, one minor, and one epidemiologic criteria
  • Probable
    • One major and two minor criteria
    • One major, one minor, and one epidemiologic criteria
    • Three minor and one epidemiologic criteria

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 (variable sensitivity/specificity)
    • May be useful if used with imaging data
      • ELISA as initial testing in either serum or CSF
      • Confirm ELISA with Western blot – more sensitive (available at some laboratories; not currently available at ARUP Laboratories)

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

Background

Epidemiology

• Incidence
  • Endemic in Mexico, Central America, 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
• Symptoms begin when cyst dies; depends on where the cysts are located
• Dying cyst releases antigenic material, triggering the host inflammatory response

Clinical Presentation

• Initial infection often asymptomatic
  • Rapid onset dependent on number of cysts and body site affected
• Parenchymal
  • Most common form
  • Enhancing lesions
  • Often asymptomatic – found incidentally during imaging
  • Seizures
• Extraparenchymal
  • Intraventricular or subarachnoid space disease
  • Obstructive hydrocephalus
  • Subarachnoid disease – stroke, vasculitis, meningitis/encephalitis
• Ocular cysts
  • Usually vitreous; can be subretinal
  • Blurry or disturbed vision, swelling or retinal detachment