Cysticercosis - Taenia Solium

Cysticercosis is a parasitic infection caused by the larval stage of the pork tapeworm, Taenia solium. Diagnosis usually involves both serological testing and brain imaging.

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

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
  • Ocular cysts
    • Usually vitreous; can be subretinal
    • Blurry or disturbed vision, swelling or retinal detachment

ARUP Lab Tests

Detect the presence of CSF IgG antibodies to T. solium if 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

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

Patients with collagen vascular diseases, hepatic cirrhosis, schistosomiasis, and other parasitic infections can produce false-positive results

Medical Experts

Contributor

Couturier

Marc Roger Couturier, PhD, D(ABMM)
Associate Professor of Clinical Pathology, University of Utah
Medical Director, Parasitology/Fecal Testing, Infectious Disease Antigen Testing, Bacteriology, and Molecular Amplified Detection, ARUP Laboratories

References

Additional Resources