Tapeworm Classifications

Tapeworms are part of the worm group called Platyhelminthes. Most look like a ribbon, which is where they get the names tapeworm, flatworm and fluke. They cause harm to the body by piercing organs and blocking organ function. They also can affect the flow of oxygen, blood and nutrition. Tapeworms poison the body with their waste and destroy cells. There are around 25,000 known species of tapeworm that are divided into four classes.

Turbellaria Class

• One type of turbellaria tapeworm feeds on the polyps of jelly fish.

  The Turbellaria live in water and are typically very small (less then 1 mm long). They are usually commensal, meaning they live with other animals, not feeding on them. According to EarthLife.net, a biology education website, all Playhelminthes are believed to have evolved from turbellarians. There are five subclasses of the most common types of Turbellaria. Acoela feed on algae and live in shallow waters; Macrostomida live in both fresh and marine water and feed on the polyps of jelly fish; Polycladia are colorful worms that mostly live on the sea floor; Tricladida are the most known and studied of this group, living with other animals and are not usually parasitic; and Temnocephalida, which may be either commensals or parasites.

Cestoda Class

• Cestoda tapeworms are often a result of eating raw or undercooked meat.

  The Cestoda class affects humans most often. Infestation is called either larval or adult cestodiasis, depending on the stage of the worm living in your body. In larval stages, humans are not often their host. However, it is possible for larvae to live in humans, which can cause very serious problems, as some types of larval cestodiasis are not treatable with medicine or surgery. Adult cestodiasis is more common in but makes people less ill than the larval stage. Only large infestations cause physical damage and blockage of the intestines. The most common types of cestoda tape worms found in humans are beef tapeworm (taeniarhynchus saginatus), pork tapeworm (taenia solium), fish tapeworm (diphyllobothrium latum), dog tapeworm (diplydium caninum), and dwarf tapeworm (vampirolepis nana). Dwarf tapeworm is found in the flour beetle, while dog tapeworm often comes from dogs with fleas or lice. Beef, pork and fish tapeworm occur from eating raw or undercooked meat.

Monogenean Class

• Monogenean tapeworms might choose whales as their primary host.

  Monogeneans have no intermediate host species. The animal that the adult worm lives in is called the primary host. Animals that the early larvae stages live on are called secondary hosts. Monogeneans are ectoparasitic (living on the exterior of another organism) and are often found on the gills or skin of fish. They typically choose octopus, squid, amphibians, aquatic reptiles and whales as their primary hosts.

Trematoda Class

• Some types of trematoda tapeworms choose arthropods like crayfish as a secondary host.

  The Trematoda class contains two subclasses; Digenea and Aspidogastrea. Most Aspidogastreans use mollusks (snails) or arthropods (crab or crayfish) as the secondary or intermediate host, and a vertebrate like a fish as a primary (or adult) host.

  Digeneans typically choose mollusks as their intermediate host; their primary (adult) host is most often a vertebrate. About 12 of the 6,000 species of digeneans are infectious to humans and are divided into two groups. Schistosomiasomes live and feed inside the blood vessels of their host. They can live for several years, producing thousands of eggs which accumulate in the capillaries. Eventually some eggs escape through bodily fluids such as urine.

  Non-Schistosomiasomes never leave the intermediate host to find a primary host, forming cysts on them instead. There are seven main species of non-Schistosomiasomes that can infect humans if they are eaten as metacercarial (late stage larvae) cysts. One type lives in the lungs and the other six in the digestive system. Infection with these parasites normally causes severe discomfort but is not often life-threatening.