Lec 11 UPDATED Intro to Cestodes

Cyclophyllideans and Pseudocyclophyllideans

Cestodes, or tapeworms

constitute a class of phylum Platyhelminthes

Cyclophyllideans

has true cup-like suckers or acetabulla

Pseudocyclophyllideans

has false or slit-like grooves (bothria), (e.g. Diphyllobothrium latum)

* Flat and ribbon-like
* Living worms: white or yellowish

Cestodes: Describe the adult tapeworm

* Anterior attachment organ
* varies from species to species
* generally all cestodes (except D. latum)

\
* Four muscular, cupshaped suckers (acetabulla)
* Elongate and protrusible rostellum in the center of the scolex
* Characteristic scolex for each species can be used for diagnostic purposes

Cestodes: Describe the scolex

* shows continuous proliferation of new segments or proglottids
* Immature segment
* Mature segment
* Gravid segment

Cestodes: Describe the proglottids/strobila

Immature segment

Part of proglottids/strobila with no fully developed internal structures

Mature segment

Part of proglottids/strobila that is larger, found in the __middle of the strobila__; may contain either one or two sets of both female and male reproductive organs

Gravid segment

Part of proglottids/strobila that is found in the terminal portion, usually filled with eggs

* non operculated
* membranes have oncosphere

Cestodes: Describe the eggs

oncosphere

serve as protective coverings of the embryo, containing six elongate hooks

* Taenia saginata
* Taenia solium
* Hymenolepis nana
* Hymenolepis diminuta

INTESTINAL CESTODES

Taenia saginata

Known as beef tapeworm in humans

* Humans serve only as definitive host
* No human cysticercosis for this species
* Inhabits the jejunum

Taenia saginata

Jejunum

Taenia saginata inhabits what part of the intestine?

Taenia saginata

* Cuboidal scolex measuring 1-2mm in diameter
* Has 4 prominent acetabula
* __Devoid of hooks or rostellum__

Devoid of hooks or rostellum

Describe the rostellum of Taenia saginata

Taenia saginata

* Adults measure 4-10m
* May have 1,000 – 4,000 proglottids
* Mature proglottids are square-shaped, containing mature male and female reproductive organs

Taenia saginata

* Has 2 large lobes or ovaries and median club-shaped uterus
* 300 to 400 follicular testes scattered
* Vagina contains a sphincter

Taenia saginata

* Gravid proglottids are longer than wide; contains 97,000 to 124,000 ova
* Uterus with ova has __15 to 20 lateral branches__
* Genital pores are __irregularly alternate__

Taenia saginata

* Morphologically same among Taenia spp.
* Has spherical or subspherical shape measuring 30 to 45 um

Taenia saginata

* Brownish with thick striated embryophore
* Contains oncosphere or embryo with three pairs of hooklets

Ingestion of encysted larvae from raw or improperly cooked beef

Taenia saginata: MOT

Taenia saginata

Can cause cysticercus bovis

Taenia saginata

* Adult worms are irritated by alcohol—sometimes there is passage of proglottids after a drinking bout
* Humans are never intermediate hosts

passage of proglottids in the stool

Most common chief complaint for T. saginata

* Epigastric pain
* Vague discomfort
* Hunger pangs
* Weakness
* Weight loss
* Loss of appetite
* Pruritus ani

Common symptomatology for T. saginata

Taenia saginata

* Entangled proglottids may cause intestinal obstruction
* Proglottids are actively motile—may cause obstruction in bile and pancreatic ducts
* May find actively motile proglottids in the perianal area and undergarments

* Usually patients bring in passed out proglottids
* Gravid proglottids may be pressed or flattened between two glass slides and examined against a light
* India ink - count lateral branches
* Eggs are irregularly passed out in stool—can do concentration technique (e.g. FECT) to increase sensitivity
* Perianal swabs

Taenia saginata: Diagnosis

India ink

Taenia saginata: Diagnosis

\
May inject _______ through the genital pore to count the lateral branches

* Praziquantel
* 5 to 10 mg/kg single dose both for adults and children

Taenia saginata: Drug of choice

* recovery of scolex; or
* negative stool examination 3 months after treatment

Taenia saginata: criteria for cure

Taenia solium

Known as pork tapeworm of man

Taenia solium

Humans are both the definitive and intermediate host

Taenia solium, scolex

* Has four acetabula, more spherical
* cushion-like rostellum with a double crown of 25 to 30 large and small hooks

cushion-like rostellum with a double crown of 25 to 30 large and small hooks

Describe rostellum of Taenia solium

Taenia solium

* Adults measure 2 to 4 um in length
* May have 8,000 to 10,000 proglottids
* Presence of accessory ovarian lobe

Taenia solium

* Has 100 to 200 follicular testes
* Gravid proglottid has 7 to 13 lateral branches containing 30,000 to 50,000 ova

measly pork

Taenia solium:

Infected meat often called what?

cysticercus cellulosae

Taenia solium:

Oncospheres encyst in muscles as

Taenia solium

May cause cysticercus cellulosae

* tongue
* heart
* diaphragm
* liver
* spleen
* mesentery

Taenia solium

Commonly affected muscles:

12 weeks

Taenia solium:

Maturity attained approximately _______ from ingestion of cysticercus

mild, non-specific abdominal complaint

Taenia solium: Clinical manifestations

T

T/F: Taenia solium is not as actively motile as Taenia saginata → obstruction less likely

* fecal-oral route by ingesting Taenia solium eggs from contaminated food or drink
* autoinfection from individuals harboring Taenia solium adult

Taenia solium: Mode of transmission (Humans as intermediate)

duodenum

Taenia solium:

Oncosphere from ingested eggs hatches in ___________, and spread to different organs throughout the bloodstream → Human cysticercosis

four suckers

Taenia solium: Humans as IH

Mature cysticercus is oval, transluscent and opaque invaginated scolex with ___________ and circlet of hooks; encapsulated

5 years

Taenia solium: Humans as IH

Most commonly encyst in striated muscle and in the brain; may survive up to ____________

Neurocysticercosis

* Most serious manifestation of cysticercosis
* Considered one of the most serious zoonotic diseases worldwide

parenchyma

Neurocysticercosis:

Cysticerci with scolex may be found in the brain __________ or floating freely in the ventricles

basal cisternal spaces

Neurocysticercosis:

may appear as large vesicular structures devoid of a scolex and are usually located in the ____________

* Parenchymal
* Extraparenchymal

Neurocysticercosis:

Two geenral forms

Parenchymal Neurocysticercosis

* focal neurologic deficits are common
* depend on location of cyst
* generalized seizures when cysts are located in the cortex

* Subarachnoid/Meningitic
* Intraventricular
* Spinal

Extraparenchymal Neurocysticercosis

Extraparenchymal Neurocysticercosis: Subarachnoid/Meningitic

* may lead to an aggressive form of NCC called racemous cysticercosis
* proliferation of cysts in the base of the brain
* poor prognosis

Extraparenchymal Neurocysticercosis: Intraventricular

* cysts usually present in the third or fourth ventricle
* often lead to obstructive hydrocephalus

Spinal

rare form of Extraparenchymal Neurocysticercosis

* Convulsions (most common)
* Visual and motor deficits
* Headache
* Vomiting

Neurocysticercosis: Clinical manifestations

* opening pressure
* elevated protein
* decreased glucose
* increased mononuclear cells
* CSF eosinophilia

Neurocysticercosis:

Spinal tap may show increased ______________

Ocular cysticercosis

* Retinal or subretinal in location
* Cysts float freely in the vitreous or aqueous humor

Ocular cysticercosis

* Clinical manifestations: intraorbital pain, photopsia, blurring of vision
* Complications: loss of vision due to chorioretinitis and vasculitis, retinal detachment

identification of characteristic proglottids, eggs or scolex

Diagnosis for Taeniasis

* Spinal tap
* CT Scan
* MRI
* Opthalmoscopy
* Tissue biopsy
* Serologic tests

Neurocysticercosis: Diagnosis

* round low-density area without surrounding enhancement after administration of contrast dye
* viable larva with no inflammation
* ring-like enhancement
* dead larva
* small calcified area within a cystic space
* dead scolex

CT scan has 3 main patterns

viable larva with no inflammation

CT scan: round low-density area without surrounding enhancement after administration of contrast dye

dead larva

CT scan: ring-like enhancement

dead scolex

CT scan: small calcified area within a cystic space

* Ophthalmoscopy
* May induce movement and/or evagination of scolex

Ophthalmic cysticercosis: Diagnosis

* Tissue biopsy
* Usually palpable

Muscular or subcutaneous cysticersi: Diagnosis

* ELISA
* EITB
* Western blot

Serologic tests for T. solium

* Praziquantel
* 5 to 10 mg/kg, single dose both for adults and children
* Niclosamide (not available locally)

Taenia solium: DOC

* Praziquantel
* 50 to 75 mg/kg divided into three doses for 30 days
* Albendazole
* 400mg twice daily fo 8 to 30 days
* Corticosteroids
* given 4 hours after the last dose

Multiple parenchymal lesions: Treatment

High dose corticosteroid therapy and mannitol

Cysticercotic encephalitis: Treatment

* Surgical removal of lesions
* Albendazole
* 10 to 15 mg/kg/day for 8 days

Neurocysticercosis Subarachnoid form: Treatment

Surgical removal of cyst

Neurocysticercosis Ventricular forms: Treatment

Surgically then praziquantel or albendazole

Ocular cysticercosis: Treatment

* Thorough cooking of meat
* Freezing -20°C for 10 days
* Proper animal handling and sanitation

Taenia solium: Prevention

Hymenolepis nana

dwarf tapeworm

Hymenolepis nana

SMALLEST tapeworm infecting humans

Hymenolepis nana

Only human tapeworm to complete its entire life cycle in a single hostà no intermediate host needed

Hymenolepis nana, scolex

* Subglobular with four cup-shaped suckers
* Has retractable rostellum armed with single row of 20 to 30 Y-shaped hooklets

retractable rostellum armed with single row of 20 to 30 Y-shaped hooklets

Describe rostellum of Hymenolepis nana

Hymenolepis nana

* Delicate strobila measuring from 25 to 45 mm in length, 1 mm in width
* Reside in ileum

short, broader

Hymenolepis nana: Proglottids

* Anterior proglottids are _______
* Posterior proglottids are _________ than long

Hymenolepis nana

* Strobila has 175 to 220 segments
* Genital pores found in the same side of the segments
* Mature proglottids has three ovoid testes and one ovary

T

T/F: Hymenolepis nana: Proglottids

When segments become gravid, testes and ovary disappear while the uterus hollows out and becomes filled with eggs

Hymenolepis nana

* Spherical or subspherical
* Colorless, or clay-colored, measuring 30 to 47 um in diameter
* Oncosphere: thin outer membrane and thick inner membrane with conspicuous bipolar thickenings, with 4 to 8 hair-like polar filaments

bipolar thickenings, 4 to 8 hair-like

Hymenolepis nana: ova (Oncosphere)

Oncosphere has thin outer membrane and thick inner membrane with conspicuous ____________,__ with ______________ polar filaments

direct and indirect

Hymenolepis nana: Life cycle

Give the 2 Dual pathways

Direct

Hymenolepis nana: Life cycle

hosts ingest eggs

Indirect

Hymenolepis nana: Life cycle

accidental ingestion of infected rice and flour beetles

enteritis

Hymenolepis nana: Pathogenesis

* Light worm burden is generally asymptomatic
* Heavy infections: there is necrosis and desquamation of intestinal epithelial cells causing ____________
* Infections may resolve spontaneously

* Demonstrations of eggs in stools
* Concentration technique

Hymenolepis nana: Diagnosis

* Praziquantel
* 25 mg/kg single dose
* Nitazoxanide
* 500mg orally for 3 days (alternative)

Hymenolepis nana: Treatment

warm climates, H. nana var. fraternal

Hymenolepis nana: Epidemiology

* Prevalent in areas with ___________ such as South America, Latin America, Mediterranean, East Asia, and Philippines
* It is familial and institutional infection common in orphanages, day care centers, and mental institutions
* Found along mice and rats is considered to be a distinct subspecie called ___________

Hymenolepis nana

It is familial and institutional infection common in orphanages, day care centers, and mental institutions

Hymenolepis nana

Good personal hygiene and environmental sanitation, rodent control, proper food storage protected from grain beetles

Hymenolepis diminuta

rat tapeworm

* Taenia solium
* Hymenolepis diminuta

Requires an intermediate host