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Flashcards in Micro Deck (110)
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1

Enterobius vermicularis

Pin worm

2

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

4

E. vermicularis presentation

perianal irritation, rarely GI probs

5

E. vermicularis Dx

Find adults and/or eggs in perianal area (sticky tape test)

6

E. vermicularis Rx

two doses of pyrental pamoate two wks apart
Rx whole family
sanitize bedclothes
Mebendazole=alternative

7

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

8

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

12

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)

13

Trichuriasis

whipworm

14

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)

15

Embryonate

non-infective-->infective

16

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

18

Hookworm

Ancylostoma duodenale (old world...Mediterranean and northern Asia)

necator americanus (new World...Americas, Africa, southern Asia, Australia)

19

Hookworm portal of entry

skin! (not gut like most things else)

20

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

21

Hookworm dz

Hookworm Gastroenteritis

22

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

23

Hookworm morphology

adults have teeth or cutting places
eggs have clear outer shell

24

Hookworm gastroenteritis Dx

eggs in feces

25

Hookworm Rx

mebendazole

26

Ascariasis lumbricoides morphology

females=30cm long
eggs have characteristic irregular outer coating (makes harder to destroy)

27

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

28

Ascarias Dx

signs and symptoms NOT useful

generally there is some suspicion of intestinal helminths based on Hx

Eggs in stool definitive

29

Ascarias Rx and prevention

Pyrantel pamoate (one dose)
mebendazole (3 doses)

Proper sewage disposal (although eggs are resistant to chemical disinfectants)

30

Ascaris life cycle

1. eggs embryonate in warm/humid environment soil
2. embryonated (now infectiou) eggs ingested
3. hatch in SI
4. Larvae enter venules or lymphatics--> pass thru heart and lung to reach alveoli
5. migrate up bronchi, ascend trachea, pass down esophagus to SI, where they mature into adults
6. females produce 200,000 eggs per day
7. eggs leave host thru feces
live for 1-2 yrs