worms in pork and people

Cestodes: "cysticerci"

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Taenia saginata is the beef tapeworm that is transmitted to humans after the ingestion of undercooked or raw beef. The worm can grow to a strand of 1,000 to 2,000 segments. Each segment is known as a proglottid, and contains both male and female reproductive organs, capable of bearing fertilized eggs. Tapeworms thrive on the diet of the host, and is dependant on their carbohydrates, but also utilizing the tissues to obtain proteins. Usually, there is only one worm that will infect the system. Despite its length, it usually does not produce any marked symptoms. Therefore, it can be quite surprising when it passes out of the body. If there are symptoms, they will include diarrhea, abdominal cramping, nervousness, nausea, and loss of appetite.

Taenia solium is the pork tapeworm, and the one capable of causing the greatest harm to the human host. It is similar to the beef tapeworm, but shorter, having fewer than 1,000 proglottids. When a tapeworm egg is ingested, the shell around the egg is dissolved in the stomach, and a living embryo called an "oncosphere" is released. After about sixty to seventy days, these oncospheres become mature bladder worms called cysticerci or "cysts" that attach to the intestinal, using a head composed of four suckers and eight hooks. When its wastes are absorbed by the host, it produces toxic effects, as well as intestinal obstruction as the worm swells. This worm can remain in a human host for twenty-five to thirty years, reaching lengths of two and one-half to three meters (eight to ten feet). Humans become infected after eating undercooked pork or smoked ham or sausage where cysts are imbedded in the tissue. Unlike the beef tapeworm, pork tapeworm infestation is usually caused by multiple worms rather than just one. Infection with the adult stage of the pork tapeworm is called taeniasis, which is not a serious health threat. However, the eggs can still be carried under the fingernails of those preparing foods or be on their skin or clothes. Eggs will appear in the stool eight to twelve weeks after eating infected pork, but eggs from a carrier can take several days to ten years to develop in another person. Infectiousness remains as long as the worm is in the intestines. Twenty to thirty thousand eggs every day can be shed into the feces of a carrier. On the other hand, the larval stage causes a much more serious condition, known as cysticercosis, producing seizures and brain deterioration that is often misdiagnosed as epilepsy. Over time, the tapeworm can riddle the brain with its grape-sized bladders, causing progressive brain deterioration to the point of death. The larvae can also develop and spread through the CNS into the muscles, heart, and eyes. Amazingly, this parasitic worm does not alert the immune system. It secretes a substance that suppresses the inflammatory response to its presence, and also controls the amount of fluid passing across its membranes from the brain. Not until the death of the worm, does the body begin to respond to the "foreigner" in its midst, when these once-protective substances are no longer produced by the worm.