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Flashcards in Wk4 GI Parasites Deck (53):
1

Three unicellular eukaryotic parasites:

Protozoans
1. Entamoeba

2. Giardia

3. Cryptosporidium

2

Life stage of nematodes, Cestodes, and trematodes in mammal host:

Juvenile and adult worms

3

Giradia mechanism:

Presence of parasite decreases absorptive surface area

diahrrea 1-2 weeks, may resolve then return

4

Form of Giardia that gets ingested:

cysts

5

Form of Giardia present in fecal matter:

Trophozoites + cysts

6

FOUL smelling diarrhea

Flatulence

Greasy stools that float

Giardia

7

Failed sanitation system (water park, drinking water)

Diarrhea 1-2 weeks --> 30 days

Cryptosporidium parvum

8

Ingestion of SMALL oocysts

disrupts epithelial microvilli --> envelopes in host cell membrane

impaired absorption, enhanced secretion

watery, frequent, NON-bloody stools

Opportunistic (HIV)

Cryptosporidium parvaum

9

Cryptosporidium form found in feces:

oocysts

10

Infectious and damage causing forms of Cryptosporidium:

Sporulated oocysts

Sporozoites

11

Bloody-MUCUSEY loose stools

can invade liver --> abcess

Dx: cysts in stool

No fever, chills, or pus

Entamoeba histolytica

--> Amebic dysentery (differentiate from Bacillary which HAS fever, chills, and pus)

12

Location for Entamoeba histolytica:

USA at risk population:

tropics --> poverty areas

homosexual males

13

Life cycle for Entomoeba histolytica on host:

ingest cysts --> trophozoites in small intestine --> migrate to colon --> cysts and trophozoites in feces

14

Disease mech for E. histolytica:

hint: "Hitsto--lytica"

tissue lysis

15

tissue abcess in upper right liver lobe

RUQ pain

fever

weight loss

Amebic hepatitis

16

TISSUE antiparasitic (completely absorbed)

free-radical forming --> DNA strand breaks

TiniDAZOLE

MetroniDAZOLE

17

Antiparasitic

intersferes with pyruvate

moderatley absorbed -- primarily luminal

less efficacy in immunocompromised with Crypto

Nitazoxanide

18

luminal antiparasitic (amebicide)

loss of visual acuity

careful with thyroid disease

Iodoquinol

19

Luminal antiparasitic

Aminoglycoside (30s subunit)

Side Fx: diarrhea

Paromomycin

20

Systemic side effects of aminoglycosides not a problem with paromomycin?

ototoxicity

nephrotoxicity

**not absorbed

21

Most common helminth (worm) infx in the US:

Enterobius vermicularis

*a round worm

22

perianal pruritis

Enterobius vermicularis

**a round worm

23

Form of E. vermicularis ingested:

pinworm eggs

**can remain viable on surfaces for 2-3 weeks

24

Life span from egg to adult Enterobius vermicularis:

1-2 months --> live for 2 months as adult

25

Where/when do Enterobius vermicularis lay their eggs?

perianal region

at night

**larva can crawl back up for retroinfection

26

Dx for Enterobius vermicularis:

Scotch tape of anal region looking for eggs in the morning

**NOT likely in stool

27

Soil transmitted round worm

9-11 mm

eggs in stool

can be in skin and lungs

blood suckers

Necator

Necator americanus/Ancylostoma duodenale

hookworms**

28

Iron deficiency anemia

Necator

OR

Trichuris trichuria

29

Recurrent raised red rash along thighs and buttocks

Autoinfection in IC pts

a few mm in size

Strongolides stercoralis

**a round worm

30

barrel shaped eggs in feces

adults 3-5 CM

finger clubbing

bloody, mucus, watery diarrhea (Fe deficiency anemia)

Trichuris trichiura

**a round worm

31

Huge worm (15-35 cm)

not common in US

1 BILLION in tropics infected per year

Ascaris

32

Charcot-Leyden crystals

eggs with THICK shells

Ascaris

33

Binds parasite B-tubulin (different than host tubulin)

inhibits motor activity and metabolism

Albendazole (better for tissue)

Mebendazole

34

Cholinergic antihelminth drugs

cause spastic muscle contraction so parasite can be swept away

Pyrantel pamoate

Levamisole

**N/V, diarrhea, poorly absorbed

35

Binds glutamate gated Cl- channels

worm paralysis and death by starvation

Spectrum: ?

Ivermectin

Nematodes - Ascaris, Strongyloides, Onchocerca

36

Typical human tape worm:

Taenia

3-10 m length

37

tapeworm

beef or pork

Taenia

38

Fish tapeworm

size ?

Diphyllobothrium

HUGE!! up to 30 ft

39

Tapeworm of liver, lungs, brain

size?

Echinococcus

tiny, a few mm

40

Morphological difference between round worms and tape worms:

tape worms are SEGMENTED

41

Competes for B12 in intestine

**maybe after eating uncooked fish

Diphyllobothrium

42

Stage of Taenia ingested from beef or pork?

cysticerci

--> grows to tapeworm in small intestine

**can become cysticerosis if migrates to muscle, brain or other tissue

43

Dogs are definitive host

not really GI illness at all

sheep farming

cysts in organs

Echinococcus

44

Tx for tapeworms that also targets GI roundworms:

MOA?

Benzimidazoles
-Albendazole, Mebendazole

B-tubulin binder
-inhibits motor function and metabolism

45

Tapeworm drug

increased permiability of parasite --> divalent cations --> contraction of worm musculature

Praziquantel

46

Cestodes?

tapeworms

47

Liver involvement

RUQ pain

Entamoeba histolytica

48

Second to malaria as most devastating parasitic disease:

schistosomiasis

**a fluke

49

Mechanism of disease for schistosomiasis:

IMMUNE response to eggs

50

infection --> days --> rash, itching

1-2 months --> F/C, cough, muscle aches

Chronic --> abd pain, HEPATOMEGALY, bloody stool/urine

increased risk of bladder cancer

schistosomiasis

51

How does Schistosoma infect humans?

lives in snails in water (sporocysts--intermediate host)

free swimming cercariae leave snail and penetrate human skin

get into blood and go to lungs, heart, then liver (thats where they mature)

migrate to bowel and bladder

300 eggs/day to blood, can live 20 years

eggs leave in feces and urine --> back to water for round 2

52

Swimmers itch

Cercarial dermatitis

53

Tx for schistosomiasis:

praziquantel

same as tapeworm drug, increases permiability

low efficacy against immature worms