Mature tapeworms live in the gut of humans or other animals.
Six different types of tapeworm (Taeniasis) can infect man. They vary in length from half a centimetre (dwarf tapeworm) to more than 20 metres (beef tapeworm) and are members of a class of worms known as Cestodes. Tapeworms were named because they are divided into segments in much the same way as a tape measure. At one end there is a head (scolex) that has a large sucker on it, and this is used to attach the worm to the inside of the gut.
Segments that are full of eggs constantly drop off from the end of the worm and pass out with the faeces and remain in the soil until eaten by another animal. When the egg is swallowed, it hatches an embryo that burrows into the muscle of the animal and remains there for the rest of that animal’s life. If the animal’s flesh is eaten, the embryo enters the gut of the new host, attaches to it and grows into a mature tapeworm.
Tiny tapeworm embryos may be found in the flesh of cattle, pigs, and fish but are destroyed by cooking. Less common tapeworms can be transmitted by fleas and other insects from rats and dogs to man, and another uncommon form passes directly from the gut of one human to another through faeces and contaminated food. Tapeworms may be caught in many parts of the world but are rare in developed countries.
There may be no symptoms of tapeworms until the numbers of worms present is quite high. When this occurs, nausea, diarrhoea, abdominal discomfort, hunger, weight loss and tiredness may occur. Sometimes patients find segments of the worm in their underclothes or bedding. Except for the rare cases where the embryo stage spreads to the brain, there are no long-term complications.
The presence of tapeworms can be confirmed by examining faeces under a microscope for the presence of segments or eggs. It is then cured by the use of appropriate medication.