Parasitic GI Infections

Question 1

define trophozoites

Answer 1

motile, feeding, reproducing form of protozoa

Question 2

cyst form of protozoa

Answer 2

thick walled, survives environment, important for transmission

Question 3

3 stages for helminth

Answer 3

egg- larva- adult

Question 4

immune response to parasites

Answer 4

eosinophils- innate immune cells

seldom eliminate parasites w/ innate alone

Question 5

entameoba histolytica transmission

Answer 5

fecal-oral, humans only

cysts ingested, trophozoites in intestine cause dysentery (both shed in feces)

Question 6

histolytica on colon biopsy

Answer 6

flask shaped ulcers in mucosa

Question 7

giardia lamblia transmission/invasion

Answer 7

fecal-oral transmission, contaminated food/water

trophs duodenum, dont invade anywhere- cysts are infectious trophs are pathogenic

Question 8

giardia pathogenesis

Answer 8

malabsorption and steatorrhea

Question 9

crypto transmission and disease

Answer 9

oocysts are infectious, trophs are pathogenic

resistant to chlorine (pools)

opportunistic in immunocompromised

Question 10

dx of crypto

Answer 10

acid fast oocysts in fecal smears

Question 11

two sources of cestodes

Answer 11

pork: taenia solium
beef: taenia saginata

Question 12

shape of taenia cestodes

Answer 12

adult worms w/ scolex w/ suckers and proglotid segment

eggs have 4 hooklets

Question 13

taenia pathogenesis

Answer 13

cysts are consumed, adults develop in small intestine

solium eggs are ingested, can form cysticeri in brain eyes and skin (neurocysticercosis)

Question 14

trematodes transmission

Answer 14

skin penetration by form released by snails into fresh water

Question 15

schistosoma pathogenesis

Answer 15

adult worms go to mesenteric veins in GI, eggs shed in stool

adult worms go to bladder, eggs shed in urine and cause urogenital schistosomiasis (blood in urine, can cause bladder cancer)

Question 16

intestinal nematodes (round worms) two kinds

Answer 16

enterobius vemicularis (pinworms) in SI

ascaris lumbercoides (colon roundworms)

Question 17

pinworm and ascaris life cycle

Answer 17

eggs ingested, larvae travel to lungs and are coughed up and swallowed

adults live in SI

Question 18

pinworm and ascaris egg shapes

Answer 18

enterobium- smooth

ascaris bumpy

Question 19

necator americanus (hookworm) transmission

Answer 19

larvae penetrate skin (thru bare feet) pass thru lungs and end up in SI

adults attach to intestinal mucosa, bleeding and anemia

Question 20

strongyloides infection

Answer 20

penetrate skin, thru lungs

can reinfect w/o leaving the host

Question 21

differentiate hookworm and strongyloides

Answer 21

hookworm eggs in fecal samples

strongyloides larvae in fecal samples (blunt end and tapered end)

Question 22

main example of antiprotozoal drugs

Answer 22

nitroimidazoles (like metronidazole)

used for giardia, entamoeba, cryptosporidia

Question 23

antihelminthic agents

Answer 23

praziquantel- damages tegument, for cestodes and trematodes

benzimidazoles- microtubule synthesis inhibition, cestodes and nematodes

ivermectin- damage invertebrate nerve and muscle cells, strongyloides, roundworms (riverblindness)