Cestodes are flat, parasitic, hermaphroditic tapeworms with complex life cycles that infect animals, including humans. Although there are multiple species of cestodes, this paper will focus on three particular species that cause human disease: Taenia solium (pork tapeworm), Taenia saginata (beef tapeworm), and Diphyllobothrium (fish tapeworm).
There are two types of infections that can develop depending on the route of infection. The first type is caused by ingesting the eggs from an adult worm (expelled in animal or human feces) which results in developing cysticerci (larval stage) within the animal or human tissues. This is known as cysticercosis. If these cysticerci develop in the central nervous system, this is called neurocysticercosis. The second type is due to ingesting the cysticerci themselves, from poorly cooked infected meat, which results in the growth and infestation of the adult tapeworm within the gastrointestinal tract. The infection with the adult tapeworm is called taeniasis if infected by the Taenia family or diphyllobothriasis if infected by Diphyllobothrium.
These tapeworm infections have significant human and veterinary disease implications as well as economic effects. Neurocysticercosis is an important cause of seizures and accounts for approximately 30% of all epilepsy cases in most developing countries.