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Micro > afebrile diarrhea caused by parasites > Flashcards

afebrile diarrhea caused by parasites Flashcards

1
Q

definitive host

A

harbors sexual stage of parasite -where they produce eggs

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2
Q

intermediate host

A

harbors asexual stage

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3
Q

monoecious

A

both male and female organs: “hermaphrodite”

vs. diocious

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4
Q

protozoan parasites

A

unicellular, eukaryotic
at least 1 nucleus
motile: cilia, flagella, +/- pseudopodia, sexual/asexual repro

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5
Q

helminths

A

worms:
nematodes
cestodes
trematodes

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6
Q

nematodes

A

non-segmented roundworms

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7
Q

cestodes

A

flat, segmented bodies with head (scolex) and segments (proglattids)
also called tapeworms

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8
Q

trematodes

A

flukes, nonsegmented flatworms

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9
Q

arthropods

A

fleas ticks, lice, etc

important VECTORS of parasitic, viral, bac diseases

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10
Q

both Giardia and Cryptosporidium parvum are acq. via..

A

food and water contaminated w. human/animal feces

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11
Q

infective stage for Giardia ?

for Crypto?

A

cyst -G

oocyst -C

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12
Q

both Giardia cysts and *Crypto oocytes are resistant to..

A

Chlorine (typical levels)

*both assoc with swimming rel. GE outbreaks

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13
Q

reservoir for both G and C

A

humans and animals

worldwide

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14
Q

G and C seasonality

A

late summer, early fall

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15
Q

G and C infectious dose?

A

low!

person-person spread is important (1-1000!!!)

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16
Q

which one (G/C) is an EC pathogen and which is an obligate IC invasive parasite?

A

Giardia: EC
Crypto: IC

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17
Q

Crypto parvum may be found ?? in who ?? and produces ??

A

anywhere in GIT of immunocomps, causes cholera-like illness

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18
Q

Giardia and Cryptosporidium ddx

A

amebiasis, bac overgrowth, Crohn ileitis, Cryptosporidium enteritis?, IBS, sprue, celiac or topical sprue

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19
Q

Giardia lamblia

2 forms:

A

flagellated protozoan

2 forms: trophozoite and cyst

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20
Q

Giardia trophozoite

motility?
inhabits?

A 
pear/tear shape, "spook"
2 nuclei, 4 pairs of flagella
motile: "falling leaf" 
found in duodenum and upper jejunum
(what you will see in diarrhea)
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21
Q

Giardia cyst

A

infectious form
formed as trophozoite dehydrates with feces as it transits large bowel
oval w. tough hyaline wall and 4 nuclei

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22
Q

what form of Giardia is in environment and resistant?

A

cyst:

can survived in moderately moist cool environments

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23
Q

most common human intestinal parasite ID’d in US?

how ??

A

Giardia

community outbreaks when fecally contam. central water supplies are ineffectively treated or pre-filtered

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24
Q

Giardia reservior

transmission

A

animals: beavers, cototes, cattle, cats, dogs
humans
fecal contam of drinking water, sometimes food
infected ppl may poop out 10^8-10^9 cysts/day may for months

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25
Q

Giardia associations

A

MALES* at higher risk
no seasonality
places: St. Petersburg, New Zealand (waterfalls)

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26
Q

ppl @ risk for Giardia

A 
travelers to endemic areas
child care kiddos
close contacts
drinking contam drinking/"outside" water
outdoor activites: backpack/camp: unfiltered water
contact with infected animas
men sex w. men
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27
Q

Giardia lamblia life cycle: trophozoites are…
grow/replicate where?
then do what??

A

noninvasive
small bowel
attach to intestinal microvillus surface with sucking disks or move about free in lumen

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28
Q

Giardia: how transform from tropho to cysts

A

dehydrates with poop as it goes from small to large bowel (encystment)

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29
Q

Giardia cysts found ???

trophozites in ??

A

hard, formed stools

diarrhea

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30
Q

host ingests this form of Giardia via ??

A

cysts

contaminated food, drink, high-risk sex (fecal-oral)

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31
Q

Giardia histo changes: if trophos adhere..

called what ???

A

cause villous atrophy, crypt hyperplasia, epi damage, extensive infiltration of LP by plasma cells, lymphos, PMNs
“lawnmower effect”

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32
Q

Giardia-inf. pt symptoms are caused by….

A

mechanical blockage of absorption of fat and protein

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33
Q

asymptomatic Giardia carriers do not have bowel histo changes but ???

A

poop out cysts at constant level or intermittently

unknown mech, homeostasis btw host imm. sys and parasite

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34
Q

Giardia immunity

A

secretory IgA Abs

B cell-independent mechanism also: parasite eradication (poorly understood)

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35
Q

Giardia acute infection onset
presentation?

fever?

A

9-15 days incubation
watery foul-smelling diarrhea w. nausea, abd distension, flatulence,

mostly afebrile (uncommon low-grade)

variable presentation in regard to other symptoms

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36
Q

how long does acute Giardia last?

additional effect?

A

3-4 days

lose 10 lbs (average)

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37
Q

Giardia chronic infection onset
persist up to ?
pt may not??
symptoms

A

follows acute
9 yrs
remember initial episode
greasy, foul-smelling stool w. wl and malabsorption

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38
Q

Giardia dx: lab

A

symptoms vary so lab findings
3 specimens 1/day or alt. days
cysts or trophos depending on poop type
organisms are shed periodically (>6 tests may have -)

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39
Q

if Giardia poop can’t be sampled quickly

A

place in fixative: polyvinyl alcohol, sep container of 10% formalin then tested with EIA kit

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40
Q

other Giardia dx methods

A

-endoscopy: collect tissue/fluid specimens
-enterotest: “duodenal string test”
left 4 hrs, moves into intestine, pulled back up, expressed (addition not replacement of still sample)
-DFA
-PCR

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41
Q

Giardia tx

A 
quniacrine (anti-protozoal)
metronidazole
furazolidone
albendazole
*all have some toxicity/side effects, monitor*
*follow-up with stool samples*
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42
Q

furazolidone mech

A

cross-link DNA, tx diarrhea and enteritis from bac/protozoal inf.

43
Q

albendazole

A

vermicidal, causes degen. alterations in tegument and intestinal cells of worm by binding to colchicine-sensitive site of tubulin–>inhibs its polymerization or assembly into microtubules–>impaired glucose uptake by larval and adult stages of susceptible parasites, depletes glycogen stores
degen. changes in ER, mitochondria of germ layer, subsequent release of lysosomes–>dec. production of ATP–>diminished energy, dies

44
Q

Giardia prev/ppx

A

proper disposal of feces
good personal hygiene
only drinking tx water

45
Q

Cryptosporidiosis parvum characteristics

stains with??

A

obligate IC protozoan parasite, minimally invasive
small (4-6 micron)
Giemsa, H&E, acid-fast

46
Q

Crypto outbreaks occur from

A

contaminated central water supplies that are ineffectively tx or pre-filtered
most frequently recognized cause of recreational (outside) water-assoc. outbreaks of gastroenteritis particularly in treated venues
(not Giardia??)

47
Q

Crypto reservoir?

transmitted via ??

A

zoonosis: mammals, birds, ruminants

fecal contamination of drinking water (sometimes food)

48
Q

Crypto-infected ppl poop out how many?? oocysts in single poop, also excrete inf. oocytes up to ?? days after diarrhea stops

A

10^8-10^9

49
Q

Crypto gender, season assoc.

A

none

50
Q

Cryptosporidiosis risk factors

A

poor sanitation, poor water supply, poor personal hygiene

day care, inf. fam member, oral-anal sex

51
Q

Crypto high risk groups

A

travelers to high endemic areas, hikers, campers (drinking streams)
men sex w. men

52
Q

pops at risk for severe disease from Crypto

A

AIDS pts, other sev. T cell comps
Antiretroviral drugs correlate with dis. protection
hypogammaglobulinemic, IgA deficient ppl
both T and B cell immunity involved

53
Q

Crypto oocyte are ?? than Giardia lamblia

A

MORE resistant to chlorine and removal by flocculation and filtration water sanitation methods
hyperchlorination (9600 ppm) somewhat effective (640x Giardia-cidal concentration!!)

54
Q

Crypto infective stage..

A

sporulated oocyst containing four motile sporozoites
reaches upper small bowel–>sporozoites get out via proteases and bile salts–>attach and infect superficial surfaces of sm. intestine epi (brush border)

55
Q

after infect sm. intestinal epi, Crypto divide asexually once (intracell.) to form ??

A

eight merozoites- in a unique vacuole IC but extracytoplasmic @ cell apex
released from intestinal milieu to infect other epithelial cells

56
Q

Crypto oocysts formed via

then ??

A

sexual reproduction: micro or macro: gametogenesis

“passed” and either autoinfect host or pooped out-resistant to outside environment

57
Q

Crypto vs. immunocompetent host: infects where ??

limited to ??

A

infects jejunum

replication restricted to epi cells of microvillous border of upper intestinal tract

58
Q

Crypto vs. imm.compromised, esp. AIDs pt: org found where ??

A

virtually entire GIT, liver, pancreas

greatly exacerbated disease

59
Q

Crypto histo changes

A

villous atropy, crypt enlargement, mononuclear infiltrates in LP

60
Q

Crypto path suggests involvement of ?? bc org induces apoptosis in neighboring cells (cause of villous atrophy)

A

cholera-like toxin

61
Q

Crypto immunity: ??? appear to control replication

A

TH1 and IgA

62
Q

Crypto signs and symps: onset??

presentation?

A

7-10 day incubation
may be asymptomatic, acute self-limiting diarrhea, or persistent diarrhea
most common: profuse explosive watery diarrhea +/- vomiting, flatulence, abd. pain, cramping

63
Q

Crypto presentation:
fever?
stools/day ??
duration ?? self limiting??

A

1/3 with low grade fever
12 stools/day (median)
2 wk duration, is self limiting

64
Q

Crypto presentation in AIDS pts: duration?

A

prolonged, chronic diarrhea lasting >2 mos

some: sev. cholera-like diarrhea with wl, 2L watery stools/day! (0.15 L/day normal)

65
Q

Crypto dx

A

acid fast oocytes in stool (special order for AF on O&P)
DFA *sn
Ag-capture ELISA
enterotest

66
Q

Crypto tx

abx?
however….

A

mostly supportive: fluid and e-lyte replacement, nutrition, antidiarrheal agents??(usually contraindicated)

nitazoxanide: only one approved in US (>1yo, not proven effected for immune compromised)

67
Q

Isospora belli actual name…

clinically indistinguishable from ??

A

Cytoisospora belli

Crypto

68
Q

Cytoisospora belli defining feature..

A

respond promptly to tx with TMP-SMX

69
Q

pts who have AIDS + Cytoisospora belli have a ??? therefore ??

A

high release rate after complete remission

need to be maintained on suppressive therapy

70
Q

Cytoisospora belli dx

blood?

A 
clinical, epi, dx tests
*peripheral eosinophilia*
stool specimens: large oocytes on modified AF stains
Charcot Leyden crystals in poop
PMS NOT observed in poop
NO serology
71
Q

Blastocystis hominid clinically indistinguishable from ??

A

Crypto

protozoan pathogen, can be carried asymptomatically

72
Q

most common cause of chronic diarrhea in HIV+ pt??

which are what?

A

microsporidia

fungal pathogens

73
Q

most common microsporidia

also most common microsporidian causing enteritis in AIDS pts

A

Enterocytozoan bieneusi

74
Q

Enterocytozoan bieneusi

A

zoonotic obligate IC pathogen (all microspor)

75
Q

Enterocytozoan bieneusi infectious stage
size comparison??
infectious mechanism??

A

spore
smaller than cyclospora, crypto (protozoa>fungi)
has a coiled polar tubule, extrustion mechanism for injecting contents of infective spore into host cells (dx for microsporidial infections)

76
Q

Enterocytozoan bieneusi affects who…

A

about 50% of AIDS pts have microspor. inf–>dev. chronic diarrhea

also traveler’s diarrhea, kissods, org transplant recipients, oldies

77
Q

Enterocytozoan bieneusi transmission

can survive??

A

directly human-human

can survived in water and food -found in surface water used for drinking

78
Q

Enterocytozoan bieneusi associations

A

no gender, no seasonality assoc

79
Q

Enterocytozoan bieneusi risk factors

A

AIDS, immunocompromis

rarely causes hyperacute diarrhea in immunocompetent ppl

80
Q

Enterocytozoan bieneusi infection occurs when this happens to host cells

A

introduction of infective sporoplasm thru polar tubule–>microspor. multiply extensively within host cytoplasm

81
Q

Enterocytozoan bieneusi immunity

A

T cells (CMI, why AIDS pts with low CD4+ are infected)

82
Q

Enterocytozoan bieneusi s/s

A

diarrhea, acalculous cholecystitis

83
Q

Enterocytozoan bieneusi dx

A

standard O&P concentration

recommended: modified trichrome stain

84
Q

Enterocytozoan bieneusi tx

A

albendazole

85
Q

Cyclospora spp. disclaimer

A

low grade fever is possible

86
Q

Cyclospora is like Crypto how so??

A

causes similar diarrhea- normal in competent ppl, esp. dangerous in AIDs pts
mildly AF+ and have EC as well as IC existence

87
Q

Cyclospora occurs in who, where ??

Chicago outbreaks linked to??

A

natives and traveler to Asia and S. america
contam. drinking water, imported fruit (rasp/strawberries)
Chicago hospital diarrhea >9 wks in half! (tap water)

88
Q

Cyclospora age and gender assoc.

A

NONE

89
Q

Cyclospora seasonality

A

warm and rainy seasons

90
Q

Cyclospora risk factors

A

US outbreaks: imported fruit (berries)

91
Q

Cyclospora oocyst is ?? when passed in stools

different from Crypto

A

NOT INFECTIVE

therefore, NO fecal-oral transmission

92
Q

Cyclospora sporulation…

A

occurs in environment after days-wks @ 22-32 degrees–>division into 2 sporocysts (each have 2 elongate sporozoites)

93
Q

?? can serve as a vehicle for transmission of Cyclospora oocytes

A

fresh produce and water

therefore can be ingested

94
Q

Cyclospora oocyts ?? in the GIT

A

“excyst”–>freeing the sporozoites–>which invade epi cells of sm. intestine

95
Q

once inside epi cells of sm. intestine, Cyclospora sporozoites do what ??

A

undergo axexula multiplication and sexual dev.–>mature into oocysts–>pooped out

96
Q

Cyclospora immunity

A

unknown

97
Q

Cyclospora onset?
presenstation??

fever?

A

1 week incubation
(infects sm. intestine) watery diarrhea, frequent, often explosive BMs
may have loss of appetite, substantial wl, bloating, inc. gas, stomach cramps, N/V muscle aches, fatigue
may have low-grade fever

98
Q

some Cyclospora-inf. ppl are

A

asymptomatic

99
Q

if Cyclospora not tx, may last how long ?

A

few days–>month or longer!

may relapse

100
Q

Cyclospora dx

size comparison to Crypto??

A

oocytes LARGER than Crypto oocytes
autofluoresce under UV Crypto doesn’t
modified AF stain (unstained (wrinkled)-light pink-deep red)
-wrinkliness of oocyst wall helps distinguish from artifact

101
Q

Cyclospora ddx

A

Cypto, Giardia

102
Q

Cyclospora tx

A

TMP-SMX unlike Crypto

103
Q

how TMP-SMX is effective

A

sulfamethoxazole:
acts like substrate inhib of dihypropteroate synthetase via
comp. inhib of p-aminobenzoic acid PABA (it’s an analog)
TMP: interferes with bac DHF reductase, inhib syn. of THF

104
Q

how to prev. cyclospora

A

clean yo fruit!

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