Parasitic Platyhelminths - Cestode

Describe Cestodes

Hermaphrodites

They include all tapeworms

They have suckers and teeth that grip the host

Their reproductive structures lie behind their short necks

They have ribbon-like structures that are beneficial for absorbing nutrients from the intestine

• Pseudophyllidean Cestodes: Have Slit-like grooves

  • Diphyllobothrium latum (fish tape worm) is the only pseudophyllidean cestode (that I care about)

• Cyclophyllidean Cestodes: Have cup-like round suckers

  • Their eggs have thin outer shells and thick, radially striated inner shells

  • They also have arrow things inside of them, these are actually hooks

Intermediate and definitive hosts of tapeworms definition

Different cause hermaphrodites:

Intermediate hosts: harbor immature forms of the parasite
*Man is intermediate for Dog and Pig tapeworm

Definitive hosts: harbors the mature forms of the parasite

Fish tape worm causative agent and its life cycle

Caused by Diphyllobothrium latum

Cycle main points:

• Unembryonated egg is shed in feces and gets embryonated in water (only)

• Eggs hatch and are ingested by crustaceans

• Becomes percercoid larvae in crustaceans

• Crustacean eaten by fish, and inside the fish, the parasite progresses to the infectious Plerocercoid stage (Fish may be eaten by another fish with no change to the parasite before reaching humans)

• Scolex stage

• Adult stage in small intestine

• Release of unembryonated eggs → Recycle

Fish tape worm disease presentation, diagnosis, and treatment

Symptoms:

• Digestive disturbances

• Vit B12 deficiency (competition) → Megaloblastic anemia

Diagnosis:

Operculated eggs in stools

Treatment:

Niclosamide/Praziquantel

Dog tape worm organism and life cycle

Echinococcus granulosus

We’re accidental hosts and that my swallow Embryonated eggs in dog or sheep feces

Describe the cysts of dog tapeworms

Hydatid cysts have an inner germinal layer that produces brood capsules and daughter cysts containing protocolizes; dogs become infected by eating these cysts

Dog tapeworm clinical presentation

Echinococcosis:

• Non-specific symptoms or asymptomatic

• 60% right hypochondriac pain

• Skin rashes

• 15% jaundice

• Cyst can rupture → Broncho-biliary fistula

• Cystic hyatid disease

  • Liver cysts cause swelling and right epigastric pain, nausea, and vomitting

  • Obstruction of bile ducts and BVs → Cholangitis / jaundice/ Cirrhosis

Dog tapeworm diagnosis

Imaging

Serology

Casoni’s intermediate test

Dog tape worm contraindication

In echinococcosis, aspiration is strongly contraindicated because it may burst the cyst, releasing their fluids into the peritoneal cavity and causing anaphylaxis

Dog tape wormtreatment

Echinococcosis drugs are not curative

Surgically remove cysts

Taenia life cycle

Human definitive host

We ingest cysticerci (from undercooked meat) and shed eggs or gravid proglottids in stools

Beef tapeworm organism and epidemiology and clinical presentation

Taenia sagitana

Epi: In poor sanitation and no meat-inspection areas

Symptoms: None or mild abdominal discomfort

Pork tape worm organism (+ specific description) and epidemiology and clinical presentation

Taenia solium
→ T. solium has a scolex (A) with four suckers and a double crown of hooks, a narrow neck, and a large strobila (2-4 m) (B) consisting of several hundred proglottids. • About 2 months after ingestion, proglottids begin to detach from the distal end and are excreted in the feces. • Each segment contains 50-60,000 fertile eggs

Epi: Endemic to countries where pigs are raised as a food source

Symptoms: None or mild abdominal discomfort (Same as Saginata)

Taeniasis diagnosis and treatment

Diagnosis: Eggs or segments stools

Treatment: Niclosamide/ Praziquantel

Dog vs pork tapeworm differential diagnosis

T- solium has 7-13 branche of the uterus

T. saginata has 15-20

Saginata has motile proglottids, and an irregularly-alternated Gonopore

Human cysticercosis

Only caused by T. solium

→ Cross into bloodstream and carried to other tissue → Encyst at terminal vesels → Neurocysticercosis & Ophthalmic cysticercosis

Neuroccysticercosis

T. solium in CNS

Parasite localized in the cerebral ventricles or basal cisterns

Symptoms: Epileptic seizures, intracranial hypertension, hydrocephalus, ocasionally, cyst may grow larger (giant cysts)

Cysts: Upon degeneration release fluid that becomes opaque and dense, and brain calcification occurs starting at the cephalic portion

Cysticercosis diagnosis

Serology

Neuroimaging

Cysticercosis treatment

Individualized based on cyst location and degree of inflammation

Antiepileptics, cysticidal drugs

Albendazole + Dexamethasone

Praziquantel

Note: No reason to use antiparasitic drugs to treat dead calcified cysts.

Surgery to resolve hydrocephalus + removal of giant cysts or intraventricular cysts