Parasitic GI Infections Flashcards
define trophozoites
motile, feeding, reproducing form of protozoa
cyst form of protozoa
thick walled, survives environment, important for transmission
3 stages for helminth
egg- larva- adult
immune response to parasites
eosinophils- innate immune cells
seldom eliminate parasites w/ innate alone
entameoba histolytica transmission
fecal-oral, humans only
cysts ingested, trophozoites in intestine cause dysentery (both shed in feces)
histolytica on colon biopsy
flask shaped ulcers in mucosa
giardia lamblia transmission/invasion
fecal-oral transmission, contaminated food/water
trophs duodenum, dont invade anywhere- cysts are infectious trophs are pathogenic
giardia pathogenesis
malabsorption and steatorrhea
crypto transmission and disease
oocysts are infectious, trophs are pathogenic
resistant to chlorine (pools)
opportunistic in immunocompromised
dx of crypto
acid fast oocysts in fecal smears
two sources of cestodes
pork: taenia solium
beef: taenia saginata
shape of taenia cestodes
adult worms w/ scolex w/ suckers and proglotid segment
eggs have 4 hooklets
taenia pathogenesis
cysts are consumed, adults develop in small intestine
solium eggs are ingested, can form cysticeri in brain eyes and skin (neurocysticercosis)
trematodes transmission
skin penetration by form released by snails into fresh water
schistosoma pathogenesis
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)
intestinal nematodes (round worms) two kinds
enterobius vemicularis (pinworms) in SI
ascaris lumbercoides (colon roundworms)
pinworm and ascaris life cycle
eggs ingested, larvae travel to lungs and are coughed up and swallowed
adults live in SI
pinworm and ascaris egg shapes
enterobium- smooth
ascaris bumpy
necator americanus (hookworm) transmission
larvae penetrate skin (thru bare feet) pass thru lungs and end up in SI
adults attach to intestinal mucosa, bleeding and anemia
strongyloides infection
penetrate skin, thru lungs
can reinfect w/o leaving the host
differentiate hookworm and strongyloides
hookworm eggs in fecal samples
strongyloides larvae in fecal samples (blunt end and tapered end)
main example of antiprotozoal drugs
nitroimidazoles (like metronidazole)
used for giardia, entamoeba, cryptosporidia
antihelminthic agents
praziquantel- damages tegument, for cestodes and trematodes
benzimidazoles- microtubule synthesis inhibition, cestodes and nematodes
ivermectin- damage invertebrate nerve and muscle cells, strongyloides, roundworms (riverblindness)
