Cestoda Flashcards
what class and phylum is tapeworms part of
Phylum phlatyhelminthes
class cestoda
Name the parts of the tapeworm
scolex- has rings of hooks and suckers to attach to host
neckpiece- where budding occurs for new proglottids (asexual)
stobila- body
segments of proglottids- immature near the neck and hermaphrodite near middle
Gravid proglottids- the eggs that released from faeces
What type of fertilisation can tapeworms do and why
Can do cross fertilisation between proglottids; during copulation spermatozoa exchanged
self fertilisation as well bc they are HERMAPHRODITES
Opening called genital pore
Gravid proglottids form after mating
Why do tapeworms not need digestive tract, mouth or anus
cestode enclosed in a TEGUMENT (protective covering)
Secretory and absorptive function with microvilli
What other systems do cestodes have
excretory system: an excretory canal on each connected transverse canals; flame cells.
nervous system: a pair of cerebral ganglia in the scolex, lateral nerve cords along the strobila; a detached proglottid, has some movement and sensitivity.
Where are the eggs fertilised in cestodes (and trematodes)
ootype (a bubble to
meet the gametes and yolk)
What are the 2 larval stages (intermediate host)
Oncospheres
Cysticercus- when def host injests, scolex comes out and attaches to intestinal wall
Why are human infections not as severe as larval infections
By ingestion of eggs or earlier larvae, larval stages form in intermediate host
Found in skin, liver, muscle, brain
Adult cestodes that cause human infection are not as severe
Taenia saginata (beef tapeworm)
def, int, infective stages?
Definitive: humans
intermediate: catttle
Infective: adult tapeworm from cysticercus bovis
Life cycle of taenia saginata
*eggs/gravid proglottids passed in faces
- cattle eat vegetation contaminated with proglottids
*Oncospheres hatch and penetrate intestinal wall and go to muscle (becomes cysticercus)
*Humans eat undercooked contaminated beef, cysticercus becomes tapeworm (scolex attatches in small intestine)
*Produces gravid proglottids that are passed through faeces
Why is the cattle and pig more affected by the tapeworm than human
Parasite is in larval stages in intermediate host therefore more severe as it affects the muscle
Taenia solium (pork tapeworm)
def, int, infective stages?
Def: Human
Int: Pig or human (due to similarity with pig protein)
Inf: cysticercus cellulosae
Life cycle of Taenia solium
*proglottids shed with faeces and pig eat them
*Oncospheres hatch in the small intestine and form cysticercus in muscle
*Humans become infected after eating undercooked pork with cysticercus
*Adult proglottids removed with pills, larval stage found in brain/eye so harder to remove
2 conditions caused by taenia solium that can occur in humans?
Taeniasis- intestinal infection with adult tapeworm due to eating undercooked contaiminated pork. NO major health implications
Cysticerosis- When food or water become contaminated with T.solium EGGS (can be from faeces of pig) Oncospheres can hatch and spread via blood to brain and eyes
How to distinguish if its T. saginata or solium
Gravid proglottids:
< 12 (less than 12) uterine branches on proglottid=solium
>12 (more than 12) uterine branches =saginata
Scolex:
4 suckers no ring of hooks=saginata
4 suckers and 2 rows of hooks=solium
hosts:
human def host only=saginata
human can be int host as well with cysts in unusual places=solium
compare the sizes of T.solium and T.saginata
solium: 2-3 metres
saginata: >4 metres
Hymenolepis nana (dwarf tapeworm)
Def: human
Int: human (same host)/fleas
Infective stage: eggs
mode: ingesting the eggs from contaminated food
H.nana Life Cycle
- eggs passed in poo +eaten by int host + develop cysticercoids
- humans get infected if int host eaten + develops in small intestine + produce gravid proglottoids.
- Eggs passed in poo
*humans can get infected again if they ingest these eggs from their poo if hands hands not washed/ contaminated food and water.
H. nana how can autoinfection occur?
happens if eggs remain in human intestine + release hexacanth embryo which penetrates intestine villus + cycle continues.
how big is H.nana?
3-4 cm (most common in childeren)
Echinococcus granulosus (dog tapeworm)
def: dogs/wolves
int: humans/herbivores
infective: eggs
E.granulosus mode of infection in humans then dogs
human: ingesting eggs
dog:eating raw meat with cyst
E.granulosus life cycle
- lives in dogs intestine +gravid pros release eggs + passed in poo
- humans can get infected after contact with dog +ingesting its egg
- eggs hatch in intestine + release oncospheres which migrate to diff organs
*In organs they develop into hydatid cyst + can cause secondary cysts if rupture.
E granulosus size
5-8mm
how do dogs get reinfected? E granulosus
dogs get infected again if they eat herbivore like sheep with cysts
Diphyllobothrium latum order?
Order Pseudophyllidea
Diphyllobothrium latum (fish/broad tapeworm)
def: human/carnivores
1st int: cyclops
2nd int: fish
infective: plerocercoid
Diphyllobothrium latum mode?
eating plerocercoid with infected undercooked fish
D.Latum Life Cycle
*eggs passed in poo+ mature, hv oncospheres + develop into coracidia.
* Ingested by cyclops + coracidia turns to procercoid larvae
* larvae released from cyclops + eaten by 2nd host (small fish)
* migrates to deep tissue of fish + develop into plerocercoid larvae (infective stage for def host)
- humans might not eat the small fish but get the parasite after eating contaminated uncooked paratenic host fish.
What is a hyatid cyst
a fluid filled cyst that contains the immature larval form of the parasite E.granulosus.
reside mostly in liver or lungs
Why is cysticercus more severe than adult T.solium
occurs in intermediate host
found in harder places in body like brain, eye akin so harder to treat
