Cysticercosis is a parasitic tissue infection caused by larval cysts of the pork tapeworm. These larval cysts infect brain, muscle, or other tissue, and are a major cause of adult onset seizures in most low-income countries. An individual acquires cysticercosis from ingesting eggs excreted by a person who has an intestinal tapeworm. People living in the same household with a tapeworm carrier have a much higher risk of getting cysticercosis than others.

Cysticercosis is not acquired by eating undercooked pork -- rather, it is the tapeworm infection that is acquired by eating undercooked pork containing the larval cysts. Pigs become infected by ingesting tapeworm eggs in the feces of the human tapeworm carrier.

Both the tapeworm infection, also known as taeniasis, and cysticercosis occur globally, with the highest rates found in areas of Latin America, Asia, and Africa that have poor sanitation and free-ranging pigs raised with access to human feces. Although uncommon, cysticercosis can occur in people who have never traveled outside of the United States. Tapeworm eggs contained in fecally contaminated food are occasionally eaten in the United States. For example, a person with poor hygiene who is an asymptomatic tapeworm carrier might accidentally contaminate food while preparing it for others.

In the United States, cysticercosis is considered one of the Neglected Parasitic Infections, a group of five parasitic diseases that have been targeted by CDC for public health action.

Image: Center is an image of a Taenia egg at a high magnification of 400x. When consumed by humans Taenia eggs can lead to cysticercosis, including a serious condition known as neurocysticercosis. On the left and right are x-ray images of humans with neurocysticercosis. The darker regions are cysts in the brain of the patient.
Credit (L to R): Westchester Medical Center, PHIL, The Cysticercosis Working Group in Peru.