Taeniasis & Cysticercosis

Key Features

Essentials of Diagnosis

• Mild abdominal pain; passage of worm segments (taeniasis)

• Focal seizures, headaches (neurocysticercosis)

• Cysticerci present in biopsy specimens, on plain radiographs (as calcified masses), or on CT scan or MRI

• Proglottids and eggs in feces; specific antibodies in serum or cerebrospinal fluid (CSF)

General Considerations

• Pigs are the usual intermediate host of the tapeworm Taenia solium

• Human cysticercosis occurs when the eggs, which are excreted in the feces of a person infected with the parasite, are ingested

• Cysticercosis cannot be acquired by eating pork

  • Ingestion of infected pork results in adult tapeworm infection (taeniasis) because infected pork contains the larval cysts that develop into the adult tapeworm

  • Infected pork does not contain the eggs that cause cysticercosis

• Larvae released from ingested eggs enter the circulation to encyst in a variety of tissues, especially muscle and brain

• Full larval maturation occurs in 2 months, but the cysts cause little inflammation until the larvae die months to years later

• T solium and the beef tapeworm (Taenia saginata), which can cause taeniasis but not cysticercosis, are distributed worldwide

• Contamination of foods by eggs in human feces allows person-to-person spread without exposure to meat or travel to endemic areas

• Asymptomatic cases are common, but T solium is the most common helminth infection of the CNS and a leading cause of acquired epilepsy in the world

Clinical Findings

Symptoms and Signs

• Taeniasis

  • In most tapeworm infections, the only clinical manifestation is the passage of fecal proglottids, which are white, motile segments of tapeworm 1–2 cm in size

  • Children may harbor the adult worm for years and complain of abdominal pain, anorexia, and diarrhea

• Cysticercosis

  • In the parenchymatous form, the parasite lodges in tissue as a single or multiple cysts

  • Seizures are caused by pericystic inflammation, which results from granuloma formation

  • Brain cysts may remain silent or cause seizures, headache, hydrocephalus, and basilar meningitis

  • A slowly expanding mass of sterile cysts at the base of the brain may cause obstructive hydrocephalus (racemose cysticercosis)

  • Rarely, the spinal cord is involved

  • Neurocysticercosis manifests an average of 5 years after exposure, but may cause symptoms in the first year of life

  • In the eyes, cysts cause bleeding, retinal detachment, and uveitis

  • The differential diagnosis of neurocysticercosis includes

    • Tuberculous granuloma

    • Microabscesses

    • Arachnoid cyst

    • Neoplasms

    • Vascular lesions

Diagnosis

Laboratory Findings

• Eggs or proglottids may be found in feces or on the perianal skin (using the tape method employed for pinworms)

  • Eggs of both Taenia species are identical

  • The species are identified by examination of proglottids

• Peripheral eosinophilia is minimal or absent

• CSF eosinophilia is seen in 10–75% of cases of neurocysticercosis; its presence supports an otherwise presumptive diagnosis

• ELISA antibody titers are eventually positive in up to 98% ...