Parasitology Exam 2

What is the general shape of cestodes?

flat and ribbon-like

What does hermaphroditic mean?

Male and female reproductive track in same organism

what is the general morphology of cestodes?

scolex, neck, proglottids

What is a scolex?

Orientation of the worm -

• Biological holdfast

  • not for support or a physical anchor

  • not for feeding.

What is the neck?

Budding area for growth of worm, area where proglottids bud off

What is proglottids?

Worm segments that are sexually immature, sexually immature, or gravid depending on age

What are the parts of scolex

Biological holdfast

• hooks

• rostellum -anterior part— rostrum

• suckers

How does absorption of nutrients work?

Tapeworms are highly specialized and lack digestive tract

• food digested by host → tapeworm absorb nutrients directly across their tegument

  • uses pinocytosis, diffusion, facilitated diffusion, and active transport

  • nutrient absorption through tegument is assisted by microvilli called microtriches

What is the scientific name of the dwarf tapeworm

Hymenolepsis nana

What does the Hymenolepsis nana scolex contains

4 suckers and hooks on rostellum

What is Hymenolepsis nana direct life cycle

1. embryonated eggs in feces

2. egg ingested by insect

   1. cysticercoid develops in insect

3. Human and rodents are infected when they ingest cysticercoid-infected arthropods

4. embrynoated egg ingested by humans from contaminated food, water, or hands

5. Oncosphere hatches cysticercoid develops in intestinal villus

6. scolex

7. adult in ileal portion of small intestine

8. eggs can be released through the genital atrium of the gravid proglottids.

   1. gravid proglottiids can disintegrate releasing eggs that passed in the stools

9. autoinfection can occur if eggs remain in the intestine.

   1. eggs the release the hexacanth embryo, which penetrates the intestinal villus → contiunes cycle

   
   

What is the difference between indirect and direct lc of dwarf tapeworm

Direct - ingestion of eggs or mouse pill

indirect - ingest larvae via ingestion of insects (tenebrio beetle)

does the drawf tapeworm need a interal host?

No

what symptoms does Hymenolepsis nana have

Asymptomatic to mild symptoms – irritation to gut wall

what allergic reaction does Hymenolepsis nana cause

• Nervousness

• Headache

• Dizzy

• Diarrhea

What are the two species of Taenia tapeworm

• Taenia saginata – Beef tapeworm

• Taenia solium – Pork tapeworm

What is the scientific name of the beef tapeworm

Taenia saginata

what is the average size of the Taenia saginata

5-10 meters, up to 25 meters

does Taenia saginata have hooks on its scolex

no

how many uterine branches does proglottids have?

more than 15

note: it is longer than wide

why can’t humans get Cysticercus bovis?

anatomical differences between humans and bovine

How can you get taenia saginata?

eating undercooked beef

How can cows get taenia saginata?

pollution of sewage in grazing areas and cattle in feed lots that are infected by feed lot workers

What are the symptoms of taenia saginata

Mild to asymptomatic → can cause

• diarrhea due to reaction to worm metabolites

• potentially cause small intestinal blockage

How to prevent getting beef tapeworm

• Inspect beef

• cook beef

• clean grazing areas

• uninfected feed lot workers

What is the scientific name of pork tapeworm

taenia solium

How long can taenia solium get?

2-8 meters

What does Taenia solium have on its scolex

hooks and suckers

How many uterine branches does taenia solium have on its proglottids

less than 13 uterine branches