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Flashcards in afebrile diarrhea caused by parasites Deck (104):
1

definitive host

harbors sexual stage of parasite -where they produce eggs

2

intermediate host

harbors asexual stage

3

monoecious

both male and female organs: "hermaphrodite"
vs. diocious

4

protozoan parasites

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

5

helminths

worms:
nematodes
cestodes
trematodes

6

nematodes

non-segmented roundworms

7

cestodes

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

8

trematodes

flukes, nonsegmented flatworms

9

arthropods

fleas ticks, lice, etc
*important VECTORS of parasitic, viral, bac diseases*

10

both Giardia and Cryptosporidium parvum are acq. via..

food and water contaminated w. human/animal feces

11

infective stage for Giardia ?
for Crypto?

cyst -G
oocyst -C

12

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

Chlorine (typical levels)
*both assoc with swimming rel. GE outbreaks

13

reservoir for both G and C

humans and animals
worldwide

14

G and C seasonality

late summer, early fall

15

G and C infectious dose?

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

16

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

Giardia: EC
Crypto: IC

17

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

anywhere in GIT of immunocomps, causes cholera-like illness

18

Giardia and Cryptosporidium ddx

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

19

Giardia lamblia
2 forms:

flagellated protozoan
2 forms: trophozoite and cyst

20

Giardia trophozoite

motility?
inhabits?

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)

21

Giardia cyst

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

22

what form of Giardia is in environment and resistant?

cyst:
can survived in moderately moist cool environments

23

most common human intestinal parasite ID'd in US?
how ??

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

24

Giardia reservior

transmission

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

25

Giardia associations

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

26

ppl @ risk for Giardia

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

27

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

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

28

Giardia: how transform from tropho to cysts

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

29

Giardia cysts found ???
trophozites in ??

hard, formed stools
diarrhea

30

host ingests this form of Giardia via ??

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

31

Giardia histo changes: if trophos adhere..

called what ???

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

32

Giardia-inf. pt symptoms are caused by....

mechanical blockage of absorption of fat and protein

33

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

poop out cysts at constant level or intermittently
(unknown mech, homeostasis btw host imm. sys and parasite)

34

Giardia immunity

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

35

Giardia acute infection onset
presentation?


fever?

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

36

how long does acute Giardia last?
additional effect?

3-4 days
lose 10 lbs (average)

37

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

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

38

Giardia dx: lab

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 -)


39

if Giardia poop can't be sampled quickly

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

40

other Giardia dx methods

-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

41

Giardia tx

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

42

furazolidone mech

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

43

albendazole

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

Giardia prev/ppx

proper disposal of feces
good personal hygiene
only drinking tx water

45

Cryptosporidiosis parvum characteristics

stains with??

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

46

Crypto outbreaks occur from

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

Crypto reservoir?
transmitted via ??

zoonosis: mammals, birds, ruminants
fecal contamination of drinking water (sometimes food)

48

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

10^8-10^9

49

Crypto gender, season assoc.

none

50

Cryptosporidiosis risk factors

poor sanitation, poor water supply, poor personal hygiene
day care, inf. fam member, oral-anal sex

51

Crypto high risk groups

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

52

pops at risk for severe disease from Crypto

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

Crypto oocyte are ?? than Giardia lamblia

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

54

Crypto infective stage..

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

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

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

56

Crypto oocysts formed via
then ??

sexual reproduction: micro or macro: gametogenesis
"passed" and either autoinfect host or pooped out-resistant to outside environment

57

Crypto vs. immunocompetent host: infects where ??
limited to ??

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

58

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

virtually entire GIT, liver, pancreas
*greatly exacerbated disease*

59

Crypto histo changes

villous atropy, crypt enlargement, mononuclear infiltrates in LP

60

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

cholera-like toxin

61

Crypto immunity: ??? appear to control replication

TH1 and IgA

62

Crypto signs and symps: onset??
presentation?




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

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


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

64

Crypto presentation in AIDS pts: duration?

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

65

Crypto dx

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

66

Crypto tx


abx?
however....

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

Isospora belli actual name...
clinically indistinguishable from ??

Cytoisospora belli
Crypto

68

Cytoisospora belli defining feature..

respond promptly to tx with TMP-SMX

69

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

high release rate after complete remission
need to be maintained on suppressive therapy

70

Cytoisospora belli dx




blood?

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

Blastocystis hominid clinically indistinguishable from ??

Crypto
protozoan pathogen, can be carried asymptomatically

72

most common cause of chronic diarrhea in HIV+ pt??
which are what?

microsporidia
fungal pathogens

73

most common microsporidia
also most common microsporidian causing enteritis in AIDS pts

Enterocytozoan bieneusi

74

Enterocytozoan bieneusi

zoonotic obligate IC pathogen (all microspor)

75

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

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

Enterocytozoan bieneusi affects who...

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

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

77

Enterocytozoan bieneusi transmission
can survive??

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

78

Enterocytozoan bieneusi associations

no gender, no seasonality assoc

79

Enterocytozoan bieneusi risk factors

AIDS, immunocompromis
*rarely* causes hyperacute diarrhea in immunocompetent ppl

80

Enterocytozoan bieneusi infection occurs when this happens to host cells

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

81

Enterocytozoan bieneusi immunity

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

82

Enterocytozoan bieneusi s/s

diarrhea, acalculous cholecystitis

83

Enterocytozoan bieneusi dx

standard O&P concentration
recommended: modified trichrome stain

84

Enterocytozoan bieneusi tx

albendazole

85

Cyclospora spp. *disclaimer*

low grade fever is possible

86

Cyclospora is like Crypto how so??

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

87

Cyclospora occurs in who, where ??
Chicago outbreaks linked to??

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

Cyclospora age and gender assoc.

NONE

89

Cyclospora seasonality

warm and rainy seasons

90

Cyclospora risk factors

US outbreaks: imported fruit (berries)

91

Cyclospora oocyst is ?? when passed in stools
**different from Crypto**

NOT INFECTIVE
therefore, NO fecal-oral transmission

92

Cyclospora sporulation...

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

93

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

fresh produce and water
therefore can be ingested

94

Cyclospora oocyts ?? in the GIT

"excyst"-->freeing the sporozoites-->which invade epi cells of sm. intestine

95

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

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

96

Cyclospora immunity

unknown

97

Cyclospora onset?
presenstation??



fever?

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

some Cyclospora-inf. ppl are

asymptomatic

99

if Cyclospora not tx, may last how long ?

few days-->month or longer!
may relapse

100

Cyclospora dx
size comparison to Crypto??

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

Cyclospora ddx

Cypto, Giardia

102

Cyclospora tx

TMP-SMX *unlike Crypto*

103

how TMP-SMX is effective

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

how to prev. cyclospora

clean yo fruit!

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