Cestodes

Question 1

Order and class of cestodes

Answer 1

order = Platyhelminthes
Class = Cestoda

Question 2

Cestodes features

Answer 2

• anterior holdfast
• elongate body (strobila) with series of reproductive units
• no gastrointestinal tract

Question 3

what are proglottids

Answer 3

reproductive units

Question 4

Principles of cestode Transmission

Answer 4

Mostly ‘passive’ transfer - relies on predation by host : Direct- cats/dog
Accidental - large herbivores
eggs never hatch in external environment except Spirometra
Egg survival in environment
- eggs viable at 29C for 1-2 months
Small- spread through environment readily
- Stay sheep on St Kilda infected with larval Taenia ovis
-eggs transported by birds from larger land masses

Question 5

The two orders of cestodes

Answer 5

cyclophyllidea and pseudophyllidea

Question 6

the three family of cyclophyllidea

Answer 6

Family Taeniidae
Family Dilepididae
Family Anoplocephalidae

Question 7

explain the family taeniidae

Answer 7

• numerous species belonging to 2 genera • Taenia
• Echinococcus
• Adult tapeworm in gi tract of carnivorous
animals – humans, dogs, cats
• Larval tapeworm stage in prey animal:
– Larva is called a metacestode
– Found in solid tissues of intermediate host
– Family Taeniidae distinctive in that metacestodes are ALWAYS found in mammals

Question 8

life cycle of Tania saginata?

Answer 8

egg (oncosphere) –> ingested by mammal intermediate host , metacestode is usually species and site specific –> Definitive Host is carnivore/omnivore, Adults in Small Intestine

Question 9

explain the metacestodes of family taeniidae

Answer 9

• Always found in a mammal host
– Other tapeworms use invertebrates as intermediate host, for most species
• Three forms:
Cysticercus
Hydatid Cyst
Coenurus

Question 10

Explain Cysticercus

Answer 10

Characteristic of species of genus Taenia
One infective tapeworm larva in a bladder
Host tissues- muscle, liver, brain
Size >1 cm
(Oh…..a variant of cysticercus is the strobilocercus… a cysticercus, but presence of proglottids in worm body
In one species of Taenia. Strobilocercus found in liver of intermediate hosts

Question 11

Hydatid Cyst

Answer 11

Macroscopic cyst (golf ball, up to
basketball sized
Asexual proliferation of lining gives rise to large no’s of brood capsules. Each brood capsule contains up to 12 infective tapeworms….called protoscoleces
Many 1000’s of infective cestodes in a cyst
Hydatid cysts found in liver (eutherian mammals, or lungs (marsupials), but much variation in tissue location occurs

Question 12

rotoscoleces

Answer 12

brood capsule contains up to 12 infective tapeworms

Question 13

Coenurus

Answer 13

• A cyst in which asexual reproduction occurs, but scoleces bud directly from inner lining of cyst •Characteristic of 2 species of Taenia
• Found in muscle (lagomorphs), brain of sheep (not in Australia) •In sheep- “gid” or “staggers”

Question 14

Taenia infection problematic level

Answer 14

Infection in definitive host usually sub-clinical
• Infection in intermediate mammal host can be problematic
– Esp. Taenia solium metacestodes in humans
– Most Taenia infections in livestock of little clinical significance
– Public health significance- carcasses condemned

Question 15

Taenia solium life cycle

Answer 15

Question 16

Echinococcus

Answer 16

One species in Australia:
– E. granulosus
– Widespread
– Sheep (fertile), pigs (fertile?), cattle (not fertile), macropods (fertile), humans....
– Definitive host: dog, dingo
– Metacestode a large cyst: hydatid cyst

Question 17

Echinococcus cysts type?

Answer 17

• Cysts can be fertile (contains live protoscoleces) or infertile (protoscoleces never appear)
• In Australia, cattle and pigs are poor hosts- cysts develop by are infertile

Question 18

Echinococcus life cycle

Answer 18

Question 19

Echinococcus pathogenesis

Answer 19

Usually little effect on production ;sheep usually tolerate cysts
• In Humans-can be severe disease
– cysts produce chronic space-occupying lesions
– cause organ enlargement accompanied by various signs acute signs associated with:
cyst rupture (peritonitis, pneumothorax)
allergic responses to fluid (asthma, anaphylaxis)
• Eutherian mammals- cysts usually found in liver
• Marsupials- usually in lung!

Question 20

Echinococcus Transmission

Answer 20

• Intermediate hosts infected by ingestion of eggs
excreted by dogs
• Care in handling pets
• Worming of domesticated dogs
• Vaccine of dogs?
• Parasite extract as vaccine reduces worm size, fecundity
• Dogs infected by eating infected intermediate hosts
• Care with animal offal• Prevent dogs from feeding on wild animals

Question 21

Dipylidium cranium class and order and life cycle

Answer 21

order cyclophyllidea Fam: Dilepididae

need fleas after. dogs to work

Question 22

anoplocephalisae

Answer 22

Most likely, most common cestode of grazing animals

Question 23

Anoplocephala perfoliata pathonogenesis

Answer 23

• Cluster at ileocaecal junction
– Fatal blockage
– Colic
– UK- 20% of cases of spasmodic colic due to this species
– Moniezia
– Common cestode of sheep

Question 24

Order Pseudophyllidea

Answer 24

pirometra erinacei- zipper worm