Exam #5: Cestode & Trematode Infection Flashcards Preview

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Flashcards in Exam #5: Cestode & Trematode Infection Deck (39):
1

What are the characteristics of Cestodes?

Tapeworms
- Segmented bodies
- Hermaphoditic
- Absorb nutrients (no gut)

*Largest of the intestinal parasites (20-40 feet)

2

What are the characteristics of Trematodes?

Flukes
- Non-segmented
- Hermaphroditic
- Primitive gut

3

What are the three basic structures of adult tapeworms?

Scolex= rounded head of the worm, usually armed with hooks and suckers

Neck= area from which the new body segments are generated

Body (strobila)= a long segmented structure

4

What are individual segments of the strobila called? What is the importance of these structures?

- Proglottids
- Worms grow in length by generating new proglottids at the neck; thus, the most distal proglottids are the oldest
- Oldest proglottids are self-contained hermaphroditic structures that produce eggs (gravid)
- These gravid proglottids break off & are passed in feces

5

For which tapeworm infections are humans the definitive host?

Taenia saginota (beef tapeworm)
Taenia solium (pig tapeworm)*
Diphylobothrium lactum (fish tapeworm)

6

For which tapeworm infections are humans the intermediate host?

Echinococcus granulosus (dog tapeworm)
Taenia solium (pig tapeworm)*

7

What is Taenia saginota? Describe the lifecycle of Taenia saginota.

Beef Tapeworm

- Cattle ingest eggs/ proglottids
- Larvae invade the circulation
- Encystation of larvae occurs in the muscle of the cow, called "cysticercus"
- Humans ingest undercooked meat containing cysts & the digestive process causes the release of cysticerci
- Scolex of the worm attaches to the intestines

*The worm will grow in the intestine until there is a mature adult tapeworm

8

What are the symptoms of Taenia saginota infection?

Generally asymptomatic
- Mild abdominal pain
- Feeling of fullness

*Note that infection can last YEARS and can grow up to 10-30 feet

9

How is Taenia saginota diagnosed?

Identification of proglottids or eggs passed by infected individual

10

What is Taenia solium? Describe the lifecycle of Taenia solium.

Pork tapeworm
- Lifecycle is essentially identical to beef tapeworm lifecycle
- Ingestion of encysted worm in pork muscle

*However, humans can become an intermediate host!

11

How do humans become an intermediate host of Taenia saginota?

- Ingested eggs hatch in the intestine & release larvae known as oncospheres
- Oncospheres burrow through the intestine & pass into circulation, where they encysts in the:
Lungs
Heart
Brain
Eye

Pathology develops because the parasite causes a space-filling lesion & because of the inflammatory response to the parasite.

12

Which is more common, beef or pork tapeworm?

Beef

13

What is the difference between intestinal & extraintestinal transmission of Taenia solium?

To get a pork tapeworm, you must EAT pork

To get systemic effects, must eat eggs of pork tapeworm, which can occur via human-human transmission

14

What is Cysticercus?

Extra-intestinal encystation of Taenia solium that creates a space filling lesion and induces localized inflammation

15

What is Neruocysticercosis?

A severe complication of extra-intestinal Taenia solium infection; encysts in brain
- Seizure
- Neurological defects

16

What is the presentation of Neurocysticercosis on MRI?

"Swiss cheese lesion"

17

How is intestinal Taenia solium diagnosed?

Proglottids or eggs in stool

18

How is extra-intestinal Taenia solium diagnosed?

Imaging
Serology

19

What is Diphyllobothrium latum?

Fish tapeworm

*This is the largest tapeworm to infect man

20

Describe the lifecycle of Diphyllobothrium latum.

- Eggs passed into water
- Egg hatches in water & is ingested by small fresh-water curstachains
- Crustachian is ingested by fresh-water fish
- Encystation of larvae occurs in the muscle of the fish
- Undercooked, raw, or pickled freshwater fish is then consumed by humans

21

What is the largest tapeworm infecting man?

Diphyllobothrium latum

22

How is Diphyllobothrium latum transmitted?

Ingestion of raw or undercooked fish

23

What are the symptoms of Diphyllobothrium latum infection?

Asymptomatic or mild
- Transient nausea, abdominal pain, diarrhea
- Infection with multiple worms can cause intestinal obstruction
- Macrocytic anemia due to Vitamin B12 deficiency may be seen in elderly

24

How is Diphyllobothrium latum diagnosed?

Eggs in stool

25

What is Echinococcus granulosus? What is it similar to?

- Dog tapeworm
- Similar to Taenia solium

26

Describe the lifecycle of Echinococcus granulosus.

- Dogs shed
- Grazing animals ingest (sheep goat)
- Dogs reingest (the dead intermediate animal)

Humans can come in contact with infected dog feces, leading to extra-intestinal encystation of oncospheres similar to the process that occurs with the pork tapeworm, Taenia solium

27

What is hydatid cyst disease?

- Infection in humans by Echinococcus granulosus oncospheres; these encyst & surround themselves in a hyaline membrane, which is called a "Hydatid cyst."
- Large fluid filled cysts containing 100-1,000 larvae
- These lead to large space-filling lesions in humans, particularly in the liver

28

What are the general features of trematodes?

- Humans are the definitive host
- Fresh water snails are intermediate host
- Larval forms are released and acquired by ingestion

29

What is Fasciolopsis buski?

Intestinal fluke

30

Describe the lifecycle of Fasciolopsis buski.

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- Infects snails
- Excreted from snails
- Attached to water chestnuts
- Ingested

31

Where is Fasciolopsis buski found?

Throughout Asia and India

32

What are the symptoms of Fasciolopsis buski infection?

Light= focal inflammation, intermittent diarrhea

Heavy= Continuous diarrhea, intestinal hemorrhage, ulceration, & abscess formation

33

How is Fasciolopsis buski diagnosed?

Eggs in stool

34

What are the liver flukes?

Fasciola hepatica
Clonorchis sinesis

35

How is Fasciola hepatica infection acquired?

Ingestion of aquatic plants

36

How is Clonorchis sinesis acquired?

Eating fish that are infected

37

What are the symptoms of Fasciola hepatica infection?

- Liver tenderness & hepatomegaly
- Fever & eosinophila
- Biliary obstruction may occur (jaundice

38

How is Fasciola hepatica diagnosed?

Eggs in feces

39

What is unique about heavy infection of Clonorchis sinesis?

Heavily infected individuals are 10-15x more likely to develop bile duct cancer

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