Cysticercosis (SIS-tuh-sir-KO-sis) is a potentially serious disease of humans caused when people ingest the eggs of a tapeworm that lives in the intestines of other humans. This tapeworm, Taenia solium, is sometimes called the “pork tapeworm” because people get this type of tapeworm from eating undercooked pork. If a pig swallows the eggs of the tapeworm (passed in human feces), the pig doesn’t develop a tapeworm in its intestines. Instead, it develops microscopic capsules (called cysts) in its muscles that contain larval tapeworms. These cysts don’t make the pig sick, but people who eat raw or undercooked pork products containing these cysts develop the tapeworm and begin passing eggs in their stools as well.
Taeniasis (TEE-nahy-uh-sis) is the presence of one or more tapeworms in the intestines. People get this tapeworm by eating cysts in undercooked pork. Most people who have the tapeworm in their intestines won’t have any symptoms, but in some cases (especially if they have many tapeworms) they may develop nausea, diarrhea, abdominal pain, fever, or constipation. A tapeworm can live in an infected person’s intestines and continue to produce eggs for 25 years! The tapeworms begin shedding eggs five to twelve weeks after the tapeworm cyst was ingested in undercooked pork. People carrying living tapeworms in their intestines will shed tapeworm eggs every day in their stool; each tapeworm can produce 250,000 eggs per day. These eggs can infect other people or pigs as soon as they are shed in the stool. The eggs they shed can survive a few weeks or months in the environment. People carrying tapeworms can be diagnosed by having their stools examined in a laboratory to look for tapeworm eggs. Infected people can be treated with medication to kill the tapeworms. The stools should be examined frequently for several months to be sure all of the tapeworms have been killed.
Humans who have T. solium tapeworms living in their intestines pose a hazard for infection to others around them if they work as foodhandlers or housekeepers and do not maintain good hand washing. People can be exposed to tapeworm eggs in food prepared by infected people who have tapeworm eggs on their hands; eating raw vegetables grown in soil containing human feces; or drinking water contaminated with human feces. When humans swallow eggs from the tapeworm, they do not develop a tapeworm. Instead, when the tapeworm egg hatches in their intestines, the larva burrows through the intestine and enters their bloodstream, where it travels until resting and developing a capsule (called a cyst) usually in the person’s muscles, nervous system, or eyes. Tapeworm cysts develop in the body (the condition called cysticercosis) around two to three months after ingesting the tapeworm eggs.
People with tapeworm cysts in their muscles usually don’t have any symptoms, or only muscle pain or lentil-sized lumps that can be felt under their skin. But if the cysts develop in the brain or spinal canal, serious consequences can develop; this condition is called neurocysticercosis (NEW-row SIS-tuh-sir-KO-sis). These cysts can sometimes remain in the brain for many years without causing any symptoms, and sometimes they simply shrivel up and leave a ‘scar’ in the brain. But if a cyst breaks open, or there are many of them present, they can trigger inflammation of the brain causing headaches, seizures, confusion, and sometimes coma and death. These symptoms develop years later as the larvae contained in the cysts die and the cysts disintegrate.
People who have cysts from T. solium in their tissues or nervous systems can be diagnosed by X-ray, CT scan, or MRI; an MRI is best at finding the cysts. If a cyst is suspected, either serum or fluid from the spinal canal can be tested for the presence of special proteins (called antigens) from the cyst; a blood test called “immuno-blotting” is recommended. Both an MRI and blood tests are usually needed for a definitive diagnosis.
People with cysts only in their muscles, or only one cyst in their brain, usually don’t require any treatment. Anti-seizure medications can sometimes control the symptoms in a person who has only a few cysts in their brain. Treatment to kill the parasites in the brain of infected persons is not always recommended, since killing the parasite can cause intense inflammation and actually cause symptoms to develop. People diagnosed with several cysts in their brain or spinal cord may need treatment to kill the larvae inside the cysts and steroids to stop the inflammation process. Cysts within the eyes usually require surgical removal.
Areas of the world where many people are infected with taeniasis and cysticercosis are Central and South America, Southeast Asia, and Central and Southern Africa. Up to 20% of people living in these areas are either carrying a tapeworm or infected with one or more cysts within their bodies. U.S. residents who have never left the country have occasionally become infected, usually by foreign-born relatives or caregivers who are carrying a living tapeworm in their intestines. Since infection with this tapeworm and the presence of cysts in the brain are not reportable in the U.S., it is difficult to establish how commonly U.S. citizens are infected, but it is estimated that 1,000 new cases per year are acquired in the U.S.
Taeniasis (human infection with the tapeworm) can be prevented by good hand hygiene, good sewage treatment systems, and by testing and treating carriers to eliminate the tapeworms. Cysticercosis (tapeworm cysts in muscle or the nervous system in humans), caused by pigs eating human feces, can be prevented by good sewage treatment practices, by confining pigs to prevent scavenging, by meat inspection to reject pigs with cysts in their muscles, and by cooking all pork products to 60 degrees Centigrade.