The larval form of the pork tapeworm Taenia solium causes cysticercosis and affects 50 million people worldwide. Disease in developed countries is usually due to immigration or foreign travel. Taeniasis (intestinal tapeworm) is acquired from ingesting cysts from undercooked pork. Eggs passed in the stool from these carriers are highly infectious and may survive in the environment for months. Humans acquire cysticercosis from the ingestion of these eggs/larva, usually through unhygienic food preparation. Once the eggs are consumed, they hatch, penetrate the bowel wall, and travel to the subcutaneous tissue, skeletal muscle, and brain, though they may involve any organ. Two distinct types of diseases exist: neurocysticercosis (which can be parenchymal or extraparenchymal) and extraneural cysticercosis. Symptoms are dependent on the affected organ system; significant morbidity is associated with ocular, cardiac, and neurologic involvement. The larval worm will eventually die and leave calcified lesions.
Intestinal taeniasis is diagnosed through egg identification on stool exam or by passage of an intact worm or worm segment. Computed tomography (CT) and magnetic resonance imaging (MRI) have facilitated recognition of neurocysticercosis with visualization of a contrast-enhancing ring lesion. Diagnosis may also be made by biopsy, serum, or cerebrospinal fluid (CSF) antibody testing. Neurocysticercosis should be strongly considered in endemic regions or in immigrants with new-onset seizures.
Neurocysticercosis. Noncontrast head CT showing new (cystic) and old (calcified) lesions of neurocysticercosis. (Photo contributors: Seth W. Wright, MD, and Universidad Peruana Cayetano Heredia, Lima, Peru.)
Management and Disposition
Seizures are treated with standard medications. Calcified lesions do not require specific anticysticercal therapy. Viable cysts can be treated with albendazole or praziquantel but should be done with expert consultation. Inpatient management is advisable if viable cysts are to be treated as inflammatory reactions may occur. Corticosteroids are recommended in this situation. Surgical intervention may be indicated for obstructing neurologic lesions or intraocular lesions.
Infection is most common in rural areas of developing countries where pigs are allowed to roam freely and ingest infected human feces. This completes the cycle and propagates infection.
Cysticercosis and taeniasis are rare in predominantly Muslim countries where eating pork is uncommon; however, cysticercosis is still possible due to ingestion of contaminated nonpork food products.
The adult tapeworm can attain a length of 20 feet or more and can live up to 20 years in the intestine.
Most people with an intestinal pork tapeworm do not have cysticercosis.
The only pathognomonic CT or MRI finding of neurocysticercosis is a 2- to 4-mm bright nodule within the cyst (“cyst with dot sign”) that represents a solid larval tapeworm.
Cysticercosis Cysts. Multiple calcified soft tissue cysts noted as an incidental finding on a lower leg radiograph in a patient with disseminated cysticercosis. The “cigar-shaped” calcifications are ...