Cestodes

•Tapeworms

•multisegmented

•flatworms

•that dwell as adults entirely in the human small intestine

Cestodes

• Taenia solium

• Taenia saginata

• Echinococcus granulosus

• Echinococcus multilocularis

• Diphyllobothrium latum

• Hymenolepsis nana

Taeniasis

•Taenia saginata (beef tapeworm)

•T. solium (pork tapeworm).

•Taenia solium can also cause cysticercosis.

•Both species are worldwide in distribution.

•Taenia solium is more prevalent in poorer communities where humans live in close contact with pigs and eat undercooked pork, and in very rare in Muslim countries.

Diagnosis

• Microscopic identification of eggs and proglottids in feces is diagnostic for taeniasis,

• but is not possible during the first 3 months following infection, prior to development of adult tapeworms.

• TAKE EXTREME CARE IN PROCESSING THE SAMPLES!

INGESTION OF EGGS CAN RESULT IN CYSTICERCOSIS!

Diagnosis

• Injection of India ink in the uterus allows visualization of the primary lateral branches. Their number allows differentiation between the two species: T. saginata has 15 to 20 branches on each side while Taenia solium has 7 to 13

• Scolex of T. saginata has 4 suckers and no hooks. T. solium has 4 suckers

in addition to a double row of hooks.

Cysticercosis

•The cestode (tapeworm) Taenia solium (pork tapeworm) is the main cause of human cysticercosis

Symptoms

Cerebral cysticercosis (or neurocysticercosis),

• seizures,

• mental disturbances,

• focal neurologic deficits,

• signs of space-occupying intracerebral lesions.

• death can occur suddenly.

Extracerebral cysticercosis can cause ocular, cardiac, or spinal

lesions with associated symptoms.

Asymptomatic subcutaneous nodules and calcified intramuscular

nodules can be encountered.

http://www.rad.washington.edu/staticpix/mskbook/CysticercosisKnees.jpg

Diagnosis

•The definitive diagnosis - demonstrating the cysticercus in the tissue involved. •Antibody detection

proglottids of Taenia saginata Proglottids of Taenia saginata

Taenia solium

Taenia solium

Scoleces of Taenia saginata Taenia solium Scoleces of Taenia saginata

Taenia saginata adult worm

Hydatidosis

•Human echinococcosis (hydatidosis, or hydatid disease) is caused by the larval stages of cestodes (tapeworms) of the genus Echinococcus.

•Echinococcus granulosus causes cystic echinococcosis, the form most frequently encountered;

• Echinococcosis (hydatid disease) results from the presence of one or more massive cysts, or hydatids, which can develop in any tissue site, including the liver, lungs, heart, brain, kidneys, and long bones.

• The clinical manifestations of this infection therefore vary greatly, depending on the site and size of the cyst, but resemble those of a slow-growing tumor that causes gradually increasing pressure.

• The rupture of a hydatid cyst may induce sudden anaphylactic shock in a previously asymptomatic individual.

Diagnosis

•The diagnosis of echinococcosis relies mainly •on findings by ultrasonography and/or other imaging techniques •supported by positive serologic tests.

Diphyllobothriasis

•Diphyllobothrium latum (the fish or broad tapeworm), the largest human tapeworm

•Diphyllobothriasis occurs in areas where lakes and rivers coexist with human consumption of raw or undercooked freshwater fish.

Diagnosis

• Microscopic identification of eggs in the stool is the basis of specific

diagnosis

Hymenolepiasis

• Hymenolepis nana (the dwarf tapeworm, adults measuring 15 to 40 mm in length)

• Hymenolepis dimnuta (rat tapeworm, adults measuring 20 to 60 cm in length). Hymenolepis diminuta is a cestode of rodents infrequently seen in humans and frequently found in rodents.

• Eggs of Hymenolepis nana are immediately infective when passed with the stool

and cannot survive more than 10 days in the external environment

• worldwide

Diagnosis

• demonstration of eggs in stool specimens