6.3.5: Survey of Cestodes

Taenia saginata

Resides: intestines

Transmission: ingestion of raw/undercooked beef containing cysticerci

Disease: mild infections - may be asymptomatic; heavier infections - may cause diarrhea, abdominal cramping and pain, as well as vague digestive complaints; sever infections - produce body weakness, loss of weight, loss of appetite, vomiting, dizziness, and anemia; acute infections may cause colon blockage, may cause the colon to rupture or burst

Other Information:

• Common name: beef tapeworm
• One of the largest tapeworms, composed of up to 2000 proglottids, may exceed 25 ft in length
• Anchors to the lumen of the small intestine via a scolex with suckers

Taenia solium

Resides: Location dependent on form acquired

• Cysticeri ingested from raw or undercooked pork - develop into mature tapeworms that reside within the intestines
• Eggs ingested - eggs hatch and larvae penetrate the intestines and migrate throughout the body to encyst as cysticerci within the host tissues

Transmission: two different forms of the parasite can be acquired

• Cysticeri ingested from raw or undercooked pork
• Eggs ingested on contaminated food or drink - due to breakdown in hygiene Disease: Different ingest forms result in different disease conditions
• Cysticeri ingested from raw or undercooked pork - develop into mature tapeworms that reside within the intestines (taeniasis) characterized by the following:
• Mild infections may be asymptomatic
• Heavier infections may cause diarrhea, abdominal cramping and pain, as well as vague digestive complaints
• Severe infections - produce body weakness, loss of weight, loss of appetite, vomiting, dizziness, anemia
• Eggs ingested - cysticerci may develop resulting in cysticercosis which is characterized by the following:
• cysticerci may develop in various organs (i.e. brain, heart muscle, eye, etc.) causing damage to the organ
• cysticerci in the brain is known as neurocysticercosis; patients may exhibit seizures, psychiatric disturbances or other neurological impairments

Other Information:

• Common name: pork tapeworm
• Patients with taeniasis may pass proglottids in their feces
• May produce 50,000 eggs per proglottid
• Scolex has an armed rostellum (suckers with hooklets) used to attach to the host’s intestines
• Most dangerous of the tapeworms due to the risk of developing cysticercosis

Hymenolepis nana

Resides: intestines

Transmission: accidental ingestion of eggs (human to human contact; fecal-oral route - fecal contamination of food or water; self inoculation - commonly especially in children; breakdown in personal hygiene)

Disease: Hymenolepiasis - asymptomatic; Heavy infections may case nausea, diarrhea, and abdominal pain, anal itching

Other Information:

• Common name: dwarf tapeworm
• Knob-like scolex
• Normally about 150 - 200 proglottids in length
• Does not require an intermediate host
• One of the common human cestode parasites worldwide
• Life cycle unique from other tapeworms due to requirement of only one host

Dipylidium caninum

Resides: intestines

Transmission: ingestion of the flea that carries the larvae

Disease: asymptomatic or may have mild gastrointestinal disturbances; most striking in small children is passing of proglottids in feces

Other Information:

• Commonly found in dogs; may also be found in wolves, coyote, foxes, or cats
• Children are highly vulnerable to infection
• Proglottids are longer than they are wide
• Each proglottid contains 2 sets of male and female organs; the proglottids each have 2 genital pores - this is where it derives its common name

Diphyllobothrium latum

Resides: intestines

Transmission: ingestion of raw or undercooked fish

Disease: Diphyllobothriasis - most infections are asymptomatic; heavy infections - abdominal discomfort, vomiting, weight loss, vitamin B12 deficiency leading to pernicious anemia; on rare occasions result in bile obstruction or gallbladder damage due to migration of proglottids

Other Information:

• Common name: broad fish tapeworm
• A member of the genera producing some of the longest tapeworms infecting humans; can grow up to 30 feet long
• Host specific to fish