Week 8 ,, Cestodes

Proglottids

Segments that form from the body ,, New segments are continuously formed in the neck region just behind the tapeworm's head (scolex), pushing older segments toward the rear. As they move back, they mature and eventually become "gravid" (packed with fertilized eggs)

Which tape worm doesn’t require an intermediate host?

Hymenolepiasis

Hymenolepiasis Definitive Host

Humans, rats, or mice

Hymenolepiasis Intermediate Host

Insects (grain beetle)

Why is autoinfection possible with Hymenolepiasis?

The eggs passed in the feces are immediately infective and can be ingested by the same host

Which Hymenolepiasis species is most commonly found in humans?

H. nana

H. diminuta (“Rat Tape Worm”)

Rats are the definitive host and humans are an incidental host

Hymenolepis nana Infective Stage

Ingestion of cysticercoid-infected arthropods and embryonated eggs in feces ,, Autoinfection can occur if eggs remain inside the intestines

Hymenolepis nana Diagnostic Stage

Embryonated eggs in feces

Hymenolepiasis Clinical Features

Generally asymptomatic ,, Prolonged infection can lead to diarrhea, weight loss, weakness, vomiting, and seizures

Hymenolepiasis Geographical Location

Occurs worldwide but more frequent in warm, dry regions ,, Crowded environments with poor sanitation

Which species does this ovum belong to?

H. nana

Which species does this ovum belong to?

H. diminuta

H. diminuta Microscopic Features

Scolex (head) has four suckers with an unarmed rostellum

H. nana Microscopic Feature

Scolex (head) has four suckers and a short rostellum with hooks (armed rostellum)

What is Taenia saginata also called?

Beef tapeworm

What is Taenia solium also called?

Pig tapeworm

Taenia saginata Geographic Distribution

Worldwide ,, Commonly found in regions where people have a tendency of eating raw beef (Africa, Latin America, Eastern Europe, and Asia)

Taenia saginata Infective Stage

Cysticercus in the tissue of the intermediate host

Taenia saginata Diagnostic Stage

Eggs and gavid proglottids in feces and are passed to the environment

T. saginata Clinical Features

Generally asymptomatic ,, Migrating proglottids can cause inflammation of the appendix and bile duct

Taeniasis

Adult tapeworm in intestine usually asymptomatic or abdominal discomfort

Cysticercosis

Larvae move out of the intestine into the host's tissue

Neurocysticercosis

Damage of the CNS by larval cysts ,, Symptoms include a wide range of neurological manifestations, including seizures, headache, intracranial hypertension, and psychiatric disturbances

T. solium Symptoms

Cysticercosis, neurocysticercosis, and cysticercosis

When should the stool specimen for T. solium be collected

On three different days

Which species does this egg belong to?

Taenia spp.

Which species does this egg belong to?

Taenia spp.

Scolex of T. solium

Contains 4 suckers with rostellum containing two rows of hooks

Scolex of T. saginata

Contains 4 large suckers without rostellum or rostellar hooks

Proglottids of T. saginata

12-30 lateral uterine branches

Proglottids of T. solium

7-13 lateral uterine branches

Identify the Species

T. saginata

Identify the Species

T. solium

Taenia solium Laboratory Diagnosis

Examination of feces for eggs or proglottids ,, Biopsy of infected tissue ,, ELISA

What is Diphyllobothriasis also known as?

Fish tapeworm

Which is the largest human tapeworm?

Fish tapeworm

Identify the Parasite

Diphyllobothrium latum

Identify the Parasite

Diphyllobothrium latum

Diphyllobothrium latum Infective Stage

Infected crustacean is ingested by small freshwater fish ,, The procercoid larva is released and develops into a plerocercoid larva

Diphyllobothrium latum Diagnostic Stage

Unembryonated eggs in feces

Diphyllobothriasis Geographic Distribution

Usually seen in the Northern Hemisphere ,, Infection can occur worldwide by exportation of freshwater fish

Diphyllobothriasis Clinical Features

Can be asymptomatic and last for decades ,, May cause diarrhea, vomiting, weight loss, and abdominal pains ,, Intestinal obstruction ,, Cholecystitis

Dipylidium caninum Definitive Hosts

Dogs and cats

Dipylidium caninum Intermediate Hosts

Fleas

Dipylidium caninum Geographical Distribution

Worldwide distribution ,, Infections have been reported in Europe, the Philippines, China, Japan, Argentina, and the United States

Dipylidium caninum Diagnostic Stage

Proglottids containing egg packets

Dipylidium caninum Infective Stage

Cysticercoid larva that develops inside the intermediate host

Identify the Species

Dipylidium caninum

Identify the Species

Dipylidium caninum

Dipylidium caninum Clinical Features

Generally asymptomatic ,, Can be chronic and include mild diarrhea, stomach upset, and itching around the rectum

Diphyllobothriasis Laboratory Diagnosis

Microscopic identification of the eggs in stool ,, Examination of proglottids in stool ,, Rosette-shaped ovaries ,, Colonoscopy

Identify the Species

Diphyllobothriasis

Identify the Species

Diphyllobothriasis

What is Echinococcus granulosus also known as?

Dog tapeworm or hydatid tapeworm

Echinococcus granulosus Geographical Distribution

Occurs worldwide in sheep-raising areas

Echinococcus granulosus Infective Stage

Ingestion of eggs due to close contact with infected dogs

Echinococcus granulosus Diagnostic Stage

Hydatid cyst located in liver, lung, or other sites

Echinococcus granulosus Intermediate Host

Sheeps

Echinococcus granulosus Accidental Host

Humans

Echinococcus granulosus Symptoms

Expanding cysts cause pressure and pain, which can lead to destruction of the tissue around the area where the cyst is located

Echinococcus granulosus in the Liver

Most common site ,, If cysts gets large enough then jaundice and portal hypertension develop ,, Rupture of cysts can cause death or anaphylactic shock

Echinococcus granulosus in the Lungs

If the cyst becomes large enough, coughing, shortness of breath, and chest pains can develop

Echinococcus granulosus Laboratory Diagnosis

Biopsy of liver, lung, or other organ that contains scoleces, brood capsules, hydatid sand, or daughter cysts in cyst fluid ,, Blood tests for antibodies ,, ELISA ,, X-ray or ultrasound scan

Identify the Species

Echinococcus granulosus