Cysticercosis

See Also

Epidemiology

Immigrants from Central America and South America comprise the greatest number of cases in the U.S.
U.S. natives comprise 15% of Cysticercosis-related deaths
Most common cause of acquired Epilepsy (30% of cases) in endemic regions within the developing world
1. Southeast Asia and India
2. Philippines
3. Sub-Saharan africa
4. Central Americ and South America
5. Mexico

Pathophysiology
Lifecycle and pathogenesis

Pork Tapeworm (Taenia Solium)
1. Tapeworms (Cestodes) are Flatworms and lack their own intestinal tract
  1. Must obtain digested molecules from their environment (in this case from intestinal tract)
2. Tapeworms are hermaphrodites, having both male and female organs within the same worm
  1. Single worm can produce fertilized eggs
3. Tapeworms (Cestodes) are long and flat
  1. Tapeworms are composed in a chain of proglotitids (box-like segments)
  2. Tapeworm head (scolex) contains suckers, and for some species hooks
    1. Tapeworm larvae attach to the intestinal mucosa via suckers, and mature to adult worms
Key points related to Cysticercosis pathogenesis
1. Tenia Solium infection originates in pigs as Tapeworm larvae (cysts)
2. Tapeworms cycle between human hosts and pigs
  1. Humans ingest Tapeworm cysts in undercooked pork
  2. Pigs ingest human feces with Tapeworm eggs
3. Ingestion of cysts does not cause Cysticercosis
  1. Cyst ingestion allows Tapeworm development
  2. Ingested eggs (not cysts) are required for Cysticercosis
4. Cysticercosis is a result of fecal-oral ingestion
  1. Cysticercosis is not due to eating undercooked pork (with cysts)
  2. Cysticercosis occurs from infected human feces
    1. Can infect Vegetarians from unwashed fruit
Humans ingest Tapeworm larvae with undercooked pork
1. Larvae attach to human gut (via scolex, a hook-like head)
2. Larvae develop into adult Tapeworms (as long as 2 to 8 meters)
3. Adult Tapeworm sheds egg bundles within gravid proglottids (worm segments)
4. Proglottids passed into human stool
  1. Proglottids and eggs may be found in human stool (under stool sample microscopy)
  2. Humans may have only mild or no symptoms during this stage of infection
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 (cysticercus)
  1. Cysticercus is a round, fluid filled cyst containing a single larval Tapeworm
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

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 (5-10 years after ingestion)
  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
Distribution
1. Brain Parenchymal Neurocysticercosis (90% of cases)
  1. Seizures (most common, occuring in 50-80% of symptomatic patients)
    1. Seizure Disorder is due to Cysticercosis in 30% of cases in endemic regions (see epidemiology above)
    2. In U.S, Cysticercosis is responsible for 2% of Seizures presenting to Emergency Department
    3. 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

MRI Brain is preferred (otherwise CT Head if MRI is not available)
Diagnostic findings suggestive of Neurocysticercosis
1. Single <2 cm lesion (however, up to 7-10 CNS cysts may be present)
2. No midline shift
3. Larval sucking parts (scolex) may be visible (pathognomonic)
Differentiating cyst stage
1. Viable non-degenerating cyst: Not contrast enhanced
2. Degenerating cyst (symptomatic): Contrast-enhancing
3. Old cysts: Calcified
Differential diagnosis
1. Tuberculosis
2. Parasitic Brain Lesions (e.g. Toxoplasmosis)
3. Brain Tumor
4. Brain Abscess
Other imaging modalities
1. Consider MRI Brain if CT Head non-diagnostic
2. Ultrasound or CT are approriate to image eye

Labs

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
Biopsy of infected tissue
Lumbar Puncture (contraindicated if CNS Mass effect)
1. Obtain head imaging first to exclude CNS Mass effect
2. Exclude other CNS diagnoses
Other findings
1. Eosinophilia on Complete Blood Count

Diagnostics

Dilated Eye Exam (fundoscopic exam)
1. Indicated before initiating therapy in patients with ocular or neurologic symptoms

Differential Diagnosis

Management

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
Skeletal Muscle lesions
1. No treatment unless painful
2. Consider surgical excision
Eye: Intraocular lesions
1. Consult ophthalmology
2. Surgical excision for intraocular lesions
Eye: Extraocular Muscle lesions
1. Consult ophthalmology
2. Surgical excision for intraocular lesions or
  1. Consider Albendazole with Corticosteroid (e.g. Dexamethasone)
Brain: Subarachnoid and intraventricular lesions
1. Ventricular shunt placed if Hydrocephalus
2. Surgical excision for most lesions or
  1. Consider Albendazole with Corticosteroid (e.g. Dexamethasone)
Brain: Parenchymal Neurocysticercosis
1. Albendazole with Dexamethasone (preferred)
  1. Do not use in massive infection
  2. Not needed in calcified lesions
Brain: Seizures
1. See Status Epilepticus for acute Seizure management
2. Seizure Prophylaxis continued for 6-12 months after radiographic resolution of lesions

Prognosis

Brain Parenchymal disease with few cysts has better outcome than extraparenchymal involvement or numerous cysts

Prevention

See Prevention of Foodborne Illness
Careful and frequent Hand Washing
Wash raw fruits and vegetables before ingesting
In endemic regions, eat only fruits and vegetables that have been cooked (or that you have peeled yourself)

Resources

CDC Cysticercosis
1. http://www.cdc.gov/parasites/cysticercosis/

References

Wang and Nguyen (2017) Crit Dec Emerg Med 31(9):13-8
Cantey (2021) Am Fam Physician 104(3): 277-87 [PubMed]
Garcia (2000) Infect Dis Clin North Am 14:97-119 [PubMed]
Kraft (2007) Am Fam Physician 76:91-8 [PubMed]
Woodhall (2014) Am Fam Physician 89(10): 803-11 [PubMed]