Flashcards in Micro Deck (110)
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Enterobius vermicularis
Pin worm
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Enterobius vermicularis Epidemiology
most common helminth infection in US
crowded conditions (i.e. daycare)
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E. vermicularis morphology
adults=small, non descript
eggs flattened on one side
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E. vermicularis presentation
perianal irritation, rarely GI probs
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E. vermicularis Dx
Find adults and/or eggs in perianal area (sticky tape test)
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E. vermicularis Rx
two doses of pyrental pamoate two wks apart
Rx whole family
sanitize bedclothes
Mebendazole=alternative
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E. vermicularis life-cycle
1. eggs on perianal folds; larvae in eggs mature w/in 4-6 hrs
2. embryonated eggs ingested by human
3. Larvae hatch in SI
4. adults in lumen of cecum
5. gravid females migrate to perianal region AT NIGHT to lay eggs
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Host
organism in which parasite lives
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Reservoir
Host which maintains parasite in nature as a source for continued transmission
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definitive host
host in which sexual reproduction takes place
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Intermediate host
host in which development occurs, possibly asexual reproduction, but
NO SEXUAL REPRODUCTION
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Soil transmitted helminths
ascariasis (MC)
trichuriasis (whipworm)
Hookworm
conducive soil=warm, moist (i.e. tropical areas)
infection may last 1-5 yrs (lifespan of worm)
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Trichuriasis
whipworm
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whipworm life-cycle
only different from pin worm cycle by embryonation in soil
1. eggs in soil/fecal matter
2. swallowed
3. hatch
4. Attach to gut wall
5. eggs excreted in feces (not infectious)
6. embryonate in soil (become infectious)
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Embryonate
non-infective-->infective
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whipworm clinical presentation
Asymptomatic/nonspecific
diarrhea +/- blood
chronic blood loss/ IBD picture
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whipworm Rx
Mebendazole or albendazole
Resolves in ~2 yrs w/out Rx
Reinfection is very common
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Hookworm
Ancylostoma duodenale (old world...Mediterranean and northern Asia)
necator americanus (new World...Americas, Africa, southern Asia, Australia)
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Hookworm portal of entry
skin! (not gut like most things else)
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Hookworm life cycle
skin-->blood-->lungs-->coughed up and swallowed----> SI
1. eggs in feces
2. Rhabdiform larva hatches
3. Filariform larva
4. Filariform larva penetrate skin
5. Adults in SI
diagnositic form=eggs
infectious form=larva
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Hookworm dz
Hookworm Gastroenteritis
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Hookworm Gastroenteritis pathophys and clinical
hookworms grasp onto intestinal villi and eat tissue
produce anticoagulant, which facilitates bleeding -->(microcytic anemia!!!)
Larval stage is migratory... can produce eosinophilia and inflamation
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Hookworm morphology
adults have teeth or cutting places
eggs have clear outer shell
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Hookworm gastroenteritis Dx
eggs in feces
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Hookworm Rx
mebendazole
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Ascariasis lumbricoides morphology
females=30cm long
eggs have characteristic irregular outer coating (makes harder to destroy)
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Ascariasis presentation
degree of dz directly related to # organisms present (which depends on # of EGGS ingested)!!
large burdens can initially lead to pneumonitis, later intestinal obstruction, w/ occasional perforation
(Can cause pancreatitis (via mechanical obstruction of biliary tree) in adults)
ball of worms--> bowel obstruction--> ischemia and perforation
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Ascarias Dx
signs and symptoms NOT useful
generally there is some suspicion of intestinal helminths based on Hx
Eggs in stool definitive
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Ascarias Rx and prevention
Pyrantel pamoate (one dose)
mebendazole (3 doses)
Proper sewage disposal (although eggs are resistant to chemical disinfectants)
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