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

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

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
Test Name and Number Recommended Use Limitations Follow Up
Cysticercosis Antibody, IgG by ELISA 0055284
Method: Semi-Quantitative Enzyme-Linked Immunosorbent Assay

Detect presence of IgG antibodies to T. solium in serum when a clinical suspicion of cysticercosis exists

Most sensitive in disseminated disease

Due to the cross-reactivity that exists between cysticercosis and echinococcus antibodies (approximately 23%) a positive result by ELISA should be confirmed by Western blot 

CT or MRI suggested for neurologic presentations of the disease

Cysticercosis Antibody, IgG by Western Blot 0055283
Method: Qualitative Western Blot

Confirm IgG antibodies to T. solium in serum or CSF

Confirm positive results from ELISA testing

Consider testing for contamination by blood or transfer of serum antibodies across the blood-brain barrier

Due to the cross-reactivity that exists between cysticercosis and echinococcus antibodies (approximately 23%) a positive result by ELISA should be confirmed by Western blot

CT or MRI suggested for neurologic presentations of the disease

Cysticercosis Antibody, IgG by ELISA (CSF) 0055285
Method: Semi-Quantitative Enzyme-Linked Immunosorbent Assay

Detect the presence of CSF IgG antibodies to T. solium, when a clinical suspicion of cysticercosis exists

Diagnosis of central nervous system infections can be accomplished by demonstrating the presence of intrathecally-produced specific antibody

Interpretation of results may be complicated by low antibody levels found in CSF, passive transfer of antibody from blood, and contamination via bloody taps

CT or MRI suggested for neurologic presentations of the disease

Cysticercosis Antibody, IgG by Western Blot (CSF) 0055282
Method: Qualitative Western Blot

Confirm IgG antibodies to T. solium in CSF

Confirm positive results from ELISA testing

Interpretation of results may be complicated by low antibody levels found in CSF, passive transfer of antibody from blood, and contamination via bloody taps

CT or MRI suggested for neurologic presentations of the disease