Taenia solium is a tapeworm which can be found in both humans and pigs. Humans pass segments and eggs in their feces, spreading them to pigs and other humans as a consequence of poor hygiene, and humans pick up the infection through consuming contaminated pork. Infection with Taenia solium can result in two different conditions: taeniasis and cysticercosis, which cause very different symptoms. Depending on which condition is caused by the infection, people can experience a range of symptoms.
The lifecyle of this tapeworm starts when eggs or segments are ingested by a human or a pig. Humans may ingest them by eating infected pork, or by consuming things like contaminated food and water, while pigs ingest them from other pigs and from contaminated fodder. Once ingested, the tapeworm can set up camp in the intestines, causing taeniasis, in which an adult tapeworm latches on to the intestines. From there, eggs and segments can be dropped in the feces. The host may be entirely unaware of the tapeworm's presence, or might experience symptoms caused by malnutrition as the tapeworm interferes with nutrient absorption.
In some cases, the tapeworm manages to enter the bloodstream, traveling to areas like the brain and skeletal muscle and encysting, causing cysticercosis or neurocysticercosis. When this happens in pigs, the pigs will die within several weeks, and if slaughtered for food before this point, humans who eat the meat can get sick. When it happens in humans, it can cause a variety of neurological symptoms which may eventually lead to death if cysts are present in the brain. These cysts can be seen in medical imaging studies of the body.
For taeniasis, medications can be administered to kill the tapeworm so that it will pass through the intestines. With cysticercosis, treatment can be a bit more complicated, depending on the location of the cysts. Medications are available, and it's also possible to use surgery to remove the cysts, depending on their location. It's important to catch the infection as early as possible, before the encysting Taenia solium have had an opportunity to cause lasting damage.
There are some steps which can be taken to avoid infection with Taenia solium. For people who consume pork, the meat should be thoroughly cooked all the way through, and people should discard meat with obvious signs of cysts. Observing careful hygiene after using the bathroom will prevent the passage of the tapeworm if someone is carrying it, and washing the hands and observing food handling precautions before preparing meals will reduce the risk of passing Taenia solium eggs or segments on in food.