Ironically enough, even though you can get tapeworms from food, tapeworms themselves are unable to eat because they don't have digestive systems. Among people in some parts of the world, especially those living in places without efficient sanitation systems, tapeworm infestations are very common. However, poor sanitation isn't the only way these parasites can get inside your body. In North America, tapeworms aren't common, but when people do get them, it's usually from eating under-cooked meat and fish.
Tapeworms are parasites, meaning that they live inside other creatures, called "hosts," and receive all their nourishment from them. They belong to a group with about 5,000 different species, and can infect all vertebrates, including humans. With their long, flat bodies, tapeworms look a lot like ribbons. Their heads contain tiny suckers or hooks that they use to anchor themselves to their host's intestines. Their bodies consist of a chain of segments, ranging from as few as three to as many as 4,000. When these segments become separated from the tapeworm, each one is capable of growing into a new tapeworm.
How Tapeworms Get Nourishment
Digesting food takes a lot of work but tapeworms have evolved an ingenious way to avoid doing it -- they let their hosts digest food for them. On the outside of their bodies, tapeworms have a skin-like covering tough enough to withstand being dissolved by digestive juices, yet porous enough to allow tiny bits of food to pass through. Even though they lack digestive systems as we know them, with mouths, stomachs and intestines, tapeworms have a primitive gut extending throughout their bodies. When muscles in the upper part of the gut contract, food gets sucked into the tapeworm's body, where cells lining the gut gobble them up like a Pac-Man, extract the nutrients, and deliver them all over the body.
How Tapeworms Reproduce
Most tapeworms are hermaphroditic, meaning that they have male as well as female reproductive organs. Each segment, or proglottid, of the tapeworm is capable of both producing and fertilizing eggs. When new segments form at the base of the tapeworm's neck, existing ones move back, so the oldest are found at the very end of the body. After fertilization, the eggs hatch and become embryos, as many as 40,000 to a segment. These embryos break free of the segment wall and are excreted in the host's feces into water or dry land, waiting to be ingested by another animal. When the embryos are swallowed and reach the new host's intestines, the larvae emerge. Some kinds stay there, but others bore through the intestinal wall to blood vessels, and are carried to muscle tissue by the circulatory system.
Getting Rid of Tapeworms
The best time to get rid of tapeworms is before they have a chance to enter your body by practicing good personal hygiene, washing food thoroughly and cooking it long enough to kill any larvae that might be present. Like most other parasites, tapeworms benefit from healthy hosts, so most infections cause little serious harm, although symptoms sometimes include nausea, abdominal pain, diarrhea and anemia. When humans and domestic animals have tapeworms, drugs that target the suckers and hooks they use to attach themselves to the walls of intestines are often prescribed. If tapeworms can't hold on any longer, they get eliminated in bodily wastes.