Cestodes

Question 1

Cestode Characteristics

Answer 1

Hermaphroditic
Monoecious
Lack digestive tract, relying on what the host eats
Need intermediate host
Absorbs food via skin
Pseudophyllidium: tapeworms with multiple “segments” (proglottids) and two bothria or “sucking grooves” as adults.

Question 2

Basic Lifecycle of Cestodes

Answer 2

eggs > 1st juvenile stage (oncosphere) > 2nd juvenile stage (metacestode) > Adult

Question 3

D. Latum Eggs

Answer 3

• Mature in environment
• Operculated
• Released through uterine pore

Question 4

D. Latum reproduction

Answer 4

Mature proglottid

Question 5

D. Latum Infective stage

Answer 5

• Plerocercoid stage, in fish
• Procercoid stage, in crustaceans (sometimes humans: sparganosis)

Question 6

D. latum Procercoid stage

Answer 6

penetrates the intestinal wall and migrates to various sites, including subcutaneous tissues, the central nervous system, and muscle, where they develop to second-stage larvae or plerocercoids.

Question 7

D. latum life cycle

Answer 7

Unemb passed in feces > Emb in water > Coracidia hatch from eggs, ingested by crustaceans > procercoid live in crustaceans > Crustacean ingested by fish > Procercoid becomes Plerocercoid larva > Large fish consumes small fish > human consumes undercooked fish > Adults attach to intestinal wall via scolex > eggs get released from proglottids.

Question 8

T. saginata & T. solium reproduction

Answer 8

Contain branched uteruses (gravid proglottids)

Question 9

T. saginata & T. solium lifecyle

Answer 9

Eggs or gravid proglottids are found in feces and passed into environment > cattle (t. sag) or pigs (t.sol) ingest infected vegetation > oncosphere hatches > penetrates intestinal wall and circulates in musculature > oncosphere becomes cysticerci in muscle > humans ingest undercooked meat > Adults remain in small intestine

Question 10

T. saginata & T. solium intermediate host

Answer 10

T. sag: cattle
T. solium: pigs

Question 11

T. saginata & T. solium adults

Answer 11

Mature and remain in small intestines

Question 12

Parasites with adults in small intestine

Answer 12

D. latum
T. saginata
T. solium
H. diminuta

Question 13

Parasites with adults in lungs

Question 14

T. pisiformes intermediate host

Answer 14

dogs

Question 15

T. pisiformes reproduction

Answer 15

• Immature proglottids contain developing reproductive organs located in scolex (head)
• Can mature to contain bilobed ovary, follicular testes, lateral genital oe, and posterior vitelline mass.

Question 16

E. granulosus & E. multilocularis Life stages

Answer 16

Oncosphere —> Metacestode (Hydatid cyst) —> Adult

Question 17

E. granulosus & E. multilocularis reproduction

Answer 17

Contain few proglottids

Question 18

E. granulosus & E. multilocularis infective stage

Answer 18

Hydatid cyst

Question 19

E. granulosus hosts

Answer 19

intermediate: sheep > dogs
definitive: human

Question 20

E. multilocularis hosts

Answer 20

multiple hosts

Question 21

E. granulosus & E. multilocularis lifecyle

Answer 21

Embryonated eggs are passed in feces > Sheep ingests oncosphere > Oncosphere hatches > larvae penetrate intestinal wall > enter circulation and end in liver or lungs > Mature to hydatid cyst in liver > Dog consumes infected organs > protoscolices replicate within cysts, growing them > scolex attaches to intestine where they mature into adults.

Question 22

D. caninum characteristics

Answer 22

4 suckers on scolex
Retractable rostelum
Dioceous life cycle

Question 23

D. caninum intermediate host

Answer 23

flea (ingestion)

Question 24

D. caninum lifecyle

Answer 24

Proglottids disintegrate and release egg packet > Egg packet is ingested by larval stage of flea > Oncosphere hatches and penetrates intestinal wall > Oncosphere becomes Cysticercoid > Infected larval stage develops into adult flea that harbors cysticercoids > Infected flea is ingested by either pet or human (typically child) > Scolex attaches to intestinal wall > Gravid proglottids are passed in feces

Question 25

H. nana characteristics

Answer 25

Dwarf tapeworm Retractable, Armed Rostellum

Question 26

H. nana reproduction

Answer 26

Gravid proglottids can be released along with the eggs in feces, or just the eggs can be released in feces.

Question 27

H. nana transmission

Answer 27

Transmission is done ingestion of embryonated eggs (direct) OR ingestion of infected insect (indirect)

Question 28

H. diminuta transmission

Answer 28

Transmission due to ingestion of infected insect

Question 29

H.diminuta intermediate host

Answer 29

Required, human or rodent

Question 30

H. nana intermediate host

Answer 30

Intermediate host isn't always required, where there is one it is an insect

Question 31

H. diminuta & H. nana lifecyles

Answer 31

Emb eggs in feces > Egg is ingested by insect > Cystercercoid develops in insect > Cystercercoid arthropod ingested by human or rodent > Oncosphere hatches and Cystercercoid develops in intestine > Adults release eggs via gravid proglottids in feces Autoinfection possible if eggs remain in intestine

Question 32

Parasite with adults in liver

Answer 32

E. granulosus E. multilocularis