Flashcards in afebrile diarrhea caused by parasites Deck (104):
harbors sexual stage of parasite -where they produce eggs
harbors asexual stage
both male and female organs: "hermaphrodite"
at least 1 nucleus
motile: cilia, flagella, +/- pseudopodia, sexual/asexual repro
flat, segmented bodies with head (scolex) and segments (proglattids)
also called tapeworms
flukes, nonsegmented flatworms
fleas ticks, lice, etc
*important VECTORS of parasitic, viral, bac diseases*
both Giardia and Cryptosporidium parvum are acq. via..
food and water contaminated w. human/animal feces
infective stage for Giardia ?
both Giardia cysts and *Crypto oocytes are resistant to..
Chlorine (typical levels)
*both assoc with swimming rel. GE outbreaks
reservoir for both G and C
humans and animals
G and C seasonality
late summer, early fall
G and C infectious dose?
person-person spread is important (1-1000!!!)
which one (G/C) is an EC pathogen and which is an obligate IC invasive parasite?
Crypto parvum may be found ?? in who ?? and produces ??
anywhere in GIT of immunocomps, causes cholera-like illness
Giardia and Cryptosporidium ddx
amebiasis, bac overgrowth, Crohn ileitis, Cryptosporidium enteritis?, IBS, sprue, celiac or topical sprue
2 forms: trophozoite and cyst
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)
formed as trophozoite dehydrates with feces as it transits large bowel
oval w. tough hyaline wall and 4 nuclei
what form of Giardia is in environment and resistant?
can survived in moderately moist cool environments
most common human intestinal parasite ID'd in US?
community outbreaks when fecally contam. central water supplies are ineffectively treated or pre-filtered
animals: beavers, cototes, cattle, cats, dogs
fecal contam of drinking water, sometimes food
infected ppl may poop out 10^8-10^9 cysts/day may for months
MALES* at higher risk
places: St. Petersburg, New Zealand (waterfalls)
ppl @ risk for Giardia
travelers to endemic areas
child care kiddos
drinking contam drinking/"outside" water
outdoor activites: backpack/camp: unfiltered water
contact with infected animas
men sex w. men
Giardia lamblia life cycle: trophozoites are...
then do what??
attach to intestinal microvillus surface with sucking disks or move about free in lumen
Giardia: how transform from tropho to cysts
dehydrates with poop as it goes from small to large bowel (encystment)
Giardia cysts found ???
trophozites in ??
hard, formed stools
host ingests this form of Giardia via ??
contaminated food, drink, high-risk sex (fecal-oral)
Giardia histo changes: if trophos adhere..
called what ???
cause villous atrophy, crypt hyperplasia, epi damage, extensive infiltration of LP by plasma cells, lymphos, PMNs
Giardia-inf. pt symptoms are caused by....
mechanical blockage of absorption of fat and protein
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)
secretory IgA Abs
B cell-independent mechanism also: parasite eradication (poorly understood)
Giardia acute infection onset
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
how long does acute Giardia last?
lose 10 lbs (average)
Giardia chronic infection onset
persist up to ?
pt may not??
remember initial episode
greasy, foul-smelling stool w. wl and malabsorption
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 -)
if Giardia poop can't be sampled quickly
place in fixative: polyvinyl alcohol, sep container of 10% formalin then tested with EIA kit
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)
*all have some toxicity/side effects, monitor*
*follow-up with stool samples*
cross-link DNA, tx diarrhea and enteritis from bac/protozoal inf.
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
proper disposal of feces
good personal hygiene
only drinking tx water
Cryptosporidiosis parvum characteristics
obligate IC protozoan parasite, minimally invasive
small (4-6 micron)
Giemsa, H&E, *acid-fast*
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
transmitted via ??
zoonosis: mammals, birds, ruminants
fecal contamination of drinking water (sometimes food)
Crypto-infected ppl poop out how many?? oocysts in single poop, also excrete inf. oocytes up to ?? days after diarrhea stops
Crypto gender, season assoc.
Cryptosporidiosis risk factors
poor sanitation, poor water supply, poor personal hygiene
day care, inf. fam member, oral-anal sex
Crypto high risk groups
travelers to high endemic areas, hikers, campers (drinking streams)
men sex w. men
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*
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!!)
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)
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
Crypto oocysts formed via
sexual reproduction: micro or macro: gametogenesis
"passed" and either autoinfect host or pooped out-resistant to outside environment
Crypto vs. immunocompetent host: infects where ??
limited to ??
replication restricted to epi cells of microvillous border of upper intestinal tract
Crypto vs. imm.compromised, esp. AIDs pt: org found where ??
virtually entire GIT, liver, pancreas
*greatly exacerbated disease*
Crypto histo changes
villous atropy, crypt enlargement, mononuclear infiltrates in LP
Crypto path suggests involvement of ?? bc org induces apoptosis in neighboring cells (cause of villous atrophy)
Crypto immunity: ??? appear to control replication
TH1 and IgA
Crypto signs and symps: onset??
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
duration ?? self limiting??
1/3 with low grade fever
12 stools/day (median)
2 wk duration, is self limiting
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)
acid fast oocytes in stool (special order for AF on O&P)
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)
Isospora belli actual name...
clinically indistinguishable from ??
Cytoisospora belli defining feature..
respond promptly to tx with TMP-SMX
pts who have AIDS + Cytoisospora belli have a ??? therefore ??
high release rate after complete remission
need to be maintained on suppressive therapy
Cytoisospora belli dx
clinical, epi, dx tests
stool specimens: large oocytes on modified AF stains
Charcot Leyden crystals in poop
PMS NOT observed in poop
Blastocystis hominid clinically indistinguishable from ??
protozoan pathogen, can be carried asymptomatically
most common cause of chronic diarrhea in HIV+ pt??
which are what?
most common microsporidia
also most common microsporidian causing enteritis in AIDS pts
zoonotic obligate IC pathogen (all microspor)
Enterocytozoan bieneusi infectious stage
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)
Enterocytozoan bieneusi affects who...
about 50% of AIDS pts have microspor. inf-->dev. chronic diarrhea
also traveler's diarrhea, kissods, org transplant recipients, oldies
Enterocytozoan bieneusi transmission
can survived in water and food -found in surface water used for drinking
Enterocytozoan bieneusi associations
no gender, no seasonality assoc
Enterocytozoan bieneusi risk factors
*rarely* causes hyperacute diarrhea in immunocompetent ppl
Enterocytozoan bieneusi infection occurs when this happens to host cells
introduction of infective sporoplasm thru polar tubule-->microspor. multiply extensively within host cytoplasm
Enterocytozoan bieneusi immunity
T cells (CMI, why AIDS pts with low CD4+ are infected)
Enterocytozoan bieneusi s/s
diarrhea, acalculous cholecystitis
Enterocytozoan bieneusi dx
standard O&P concentration
recommended: modified trichrome stain
Enterocytozoan bieneusi tx
Cyclospora spp. *disclaimer*
low grade fever is possible
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
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)
Cyclospora age and gender assoc.
warm and rainy seasons
Cyclospora risk factors
US outbreaks: imported fruit (berries)
Cyclospora oocyst is ?? when passed in stools
**different from Crypto**
therefore, NO fecal-oral transmission
occurs in environment after days-wks @ 22-32 degrees-->division into 2 sporocysts (each have 2 elongate sporozoites)
?? can serve as a vehicle for transmission of Cyclospora oocytes
fresh produce and water
therefore can be ingested
Cyclospora oocyts ?? in the GIT
"excyst"-->freeing the sporozoites-->which invade epi cells of sm. intestine
once inside epi cells of sm. intestine, Cyclospora sporozoites do what ??
undergo axexula multiplication and sexual dev.-->mature into oocysts-->pooped out
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*
some Cyclospora-inf. ppl are
if Cyclospora not tx, may last how long ?
few days-->month or longer!
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
TMP-SMX *unlike Crypto*
how TMP-SMX is effective
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