Several species of tapeworm can infect people. The two most common species are the pork tapeworm 
(Taenia solium) and the beef tapeworm (Taeniasaginata). Improperly treated human sewage may be used 
to fertilize pastures or crops. Pigs or cattle become infected by grazing in contaminated pastures or 
drinking water contaminated with tapeworm eggs from human feces. The pea-sized larvae of these tapeworms 
are deposited in certain tissues of the body of infected pigs and cattle, including the muscles. The 
infection is then transmitted to people when raw or undercooked meat containing tapeworm larvae is consumed. 
The immature tapeworm develops into the adult form in the human intestine and may remain there for many years 
if not identified and treated.

The Taenia tapeworms attach to the intestinal walls but only cause mild inflammation at the site of attachment.
 As a result, most tapeworm carriers show no symptoms (asymptomatic) and usually only become aware of the 
infection after noticing tapeworm segments in their feces. Segments of the beef tapeworm may spontaneously 
pass through the anus causing a noticeable sensation. Mild gastrointestinal symptoms, such as nausea or 
abdominal pain, can occur in infected individuals. In rare cases where the tapeworm segments migrate into 
the appendix, pancreas, or bile duct, there may be a sudden onset of severe abdominal discomfort.

Cysticercosis is a potentially serious complication of Taenia solium infection in which the larvae develop 
outside the intestinal tract. This type of infection is less common and occurs following accidental 
consumption of tapeworm eggs released from the adult worm. These eggs initially are localized in the 
anal area, but they may also contaminate the fingers or other parts of the body. Infection can occur 
in the person harboring the adult tapeworm or in other people with whom that individual comes in contact. 
The tapeworm larvae may develop in various tissues throughout the body. The most serious clinical problems 
occur when the larvae develop in the central nervous system (neurocysticercosis), potentially causing seizures 
and other neurological problems. An important aspect of this type of infection is that poor hygiene on the 
part of the individuals harboring an adult tapeworm can lead to an infection in an individual that may never 
consume meat. This is a particular problem if infected individuals are employed as food handlers.