Taenia Solium
Though humans usually serve as a definitive host, eating infected meat, fostering adult tapeworms in the intestine, and passing eggs through feces, sometimes a cysticercus (a larva sometimes called a "bladder worm") develops in the human and the human acts like an intermediate host. This happens if eggs get to the stomach, usually as a result of contaminated hands, but also of vomiting.
Cysticerci often occur in the central nervous system, which can cause major neurological problems like epilepsy and even death. The condition of having cysticerci in one's body is called Cysticercosis, and is discussed in its own article.
Eggs can be diagnosed only to the family (biology) level, but if a proglottid's uterus is stained with India ink, the number of visible uterine branches can help identify the species: unlike the Taenia saginata uteri, T.
solium uteri have only five to ten uterine branches on each side.
Infection with T. solium adults is treated with niclosamide, which is one of the most popular drugs for adult tapeworm infections, as well as for fluke infections.
As cysticercosis is a major risk, it is important to wash one's hands before eating and to suppress vomiting if a patient may be infected with T. This drug damages the parasites skin internally causing it to disintegrate and is then removed by the host's immune system.
Infection may be prevented with proper disposal of human feces around pigs, cooking meat thoroughly, and/or freezing the meat at -10oC for 5 days.
Most cases occur because infected food handlers contaminate the food.
Life cycle
Life cycle of T. Click the image to see it full-size
This infection is caused by ingestion of eggs shed in the feces of a human tapeworm carrier.
Once eggs are ingested, oncospheres hatch in the intestine, invade the intestinal wall, and migrate to striated muscles, as well as the brain, liver, and other tissues, where they develop into cysticerci. In humans, cysts can cause serious sequelae if they localize in the brain, resulting in neurocysticercosis.
The parasite life cycle is completed, resulting in human tapeworm infection, when humans ingest undercooked pork containing cysticerci. Adult tapeworms develop, (up to 2 to 7 m in length and produce less than 1000 proglottids, each with approximately 50,000 eggs) and reside in the small intestine for years.
Geographic distribution
Stained T.
Because pigs are intermediate hosts of the parasite, completion of the life cycle occurs in regions where humans live in close contact with pigs and eat undercooked pork. Prevalence rates in the United States have shown that immigrants from Mexico, Central and South America and Southeast Asia account for most of the domestic cases of cysticercosis.