Tapeworm (Taeniasis / Cysticercosis)

Most cases have no symptoms. In many cases, patients become aware of the infection by noting proglottids (segments of tapeworm) in stools or mobile Taenia saginata proglottids emerging from the anus. If they occur, symptoms are mild and non-specific and include abdominal pain, digestive disorders, excessive appetite or loss of appetite, weakness, and loss of weight.

Taeniasis results from eating raw or undercooked pork or beef contaminated with the larval stage of the pork or beef tapeworm. The larvae from the infected meat develop in the human intestine into adult tapeworms. The proglottids of the tapeworm mature and become filled with eggs. Proglottids detach and eggs are then passed in the feces. The eggs can live in the environment for months or even years. Cattle and pigs become infected when they ingest vegetation containing the eggs. The eggs hatch, develop into the larval stage, and become embedded into the animal's muscles. Person-to-person transmission may occur in Taenia solium infection, but the result is cysticercosis rather than tapeworm formation.

• Taeniasis
  Centers for Disease Control and Prevention, Laboratory Identification of Parasites of Public Health Concern
  Causal Agents; Life Cycle; Geographic Distribution; Clinical Features; Laboratory Diagnosis; Treatment
   
• Cysticercosis
  Centers for Disease Control and Prevention, Division of Parasitic Diseases
  Fact Sheet and Professional Information (DPDx-Lab Assistance)

While taeniasis is an infection by the adult beef or pork tapeworms, cysticercosis is an infection by the larval stage of the pork tapeworm, Taenia solium. Cysticercosis commonly occurs when humans accidentally ingest Taenia solium eggs. Once the eggs hatch in the human's small intestine, the larvae penetrate the lining of the small intestine and enter the bloodstream.  From here the larvae can be distributed to any organ in the body, where they form cysts. Cysts are found most frequently in skin, skeletal muscle, heart, eye, and central nervous system (CNS). Neurocysticercosis, the infection of the human CNS by Taenia solium larvae, is the major cause of acquired epilepsy in the world.

Many cases of cysticercosis probably result from a person ingesting eggs that are produced by a tapeworm living in his or her intestinal tract. People can also be infected via food or water contaminated with eggs, or via eggs present in a household or work environment. 

Due to increased immigration from Central America and travel to areas where cysticercosis is found, cysticercosis is on the rise in the US. States with the highest increase include California, Arizona, New Mexico, Texas, and Colorado.

Approximately 50 million persons are infected with both parasites worldwide. About 50,000 people die of cysticercosis annually. In the US, laws governing feeding practices and inspection of domestic food animals have largely eliminated the problem of tapeworms. An estimated 1,000 new cases of cysticercosis are diagnosed in the US each year. ​

Infected individuals can expose other individuals to Taeniasis solium eggs, often via food handling. Refrain from handling food if you know you may be infected and resume this activity only after your healthcare provider has instructed you to do so.

Infected individuals can prevent infection in animals by making sure that fecal contamination of animal food or grazing areas does not occur.

Consult your healthcare provider.

Identification of segments, eggs, or heads of the parasite in the feces diagnoses taeniasis. Diagnosis is not possible during the first three months following infection, before the development of adult tapeworms. The doctor may ask you to provide additional stool samples during a time interval. Persons who are found to have eggs or proglottids in their feces could be evaluated with a blood test since self-infection, and cysticercosis can occur.

Tapeworms are treated with oral medications. Surgery is sometimes necessary to treat cysticercosis cases in the eyes, cases that are not responsive to drug treatment, or to reduce brain swelling.

Taeniasis is found worldwide. Taenia saginata is prevalent in regions where cattle are raised: Africa, the Middle East, Central and South America, Europe, and Asia. Taenia solium is prevalent in Central and South America (especially in Mexico), Africa, Southeast Asia, Eastern Europe, and Micronesia.

When traveling in developing countries or where taeniasis has been reported, avoid eating raw or undercooked pork and other meats. Don’t eat the meat of pigs that are likely to be infected with the tapeworm and wash hands with soap and water after using the toilet and especially before handling food.