Ribbon shaped worms that infest the intestines of animals and humans. Tapeworms (cestodes) are often acquired by eating undercooked fish or meat. An adult tapeworm has a flat, segmented body and hooks or suckers on its head, by which it attaches itself to the intestinal wall.
Three large species of tapeworm are acquired by eating undercooked, infected fish, beef, and pork. The adults can grow up to 6-9 metres long. Usually, tapeworms such as this have life cycles that often involve another animal host. Tapeworms occur worldwide but infestations are largely prevented in countries that have adequate measures for disposing of sewage and inspecting meat.
The much smaller dwarf tapeworm, which is only 2.5cm long, can be acquired through accidental transfer of worm eggs in human faeces to fingers and then to mouth. This worm is most widespread in the tropics and primarily affects children.
Humans can also act as intermediate hosts to the larvae of a tapeworm for which dogs are the main host.
Regardless of their size, tapeworms from fish, beef and pork often only cause mild abdominal discomfort or diarrhoea. However, if eggs of pork worms are ingested, the hatched larvae forms cysts in body tissues. This leads to cysticeorsis, the symptoms of which are convulsions and muscle pain. Hardly ever, fish tapeworms cause anaemia. Tapeworm larvae acquired from dogs grow and develop into cysts in the lungs and liver, a condition called hydatid disease.
Diagnosis and treatment
A diagnosis is made from the presence of worm segments or eggs within the faeces. Treatment with anthelmintic drugs is often effective.