afebrile diarrhea caused by parasites Flashcards
definitive host
harbors sexual stage of parasite -where they produce eggs
intermediate host
harbors asexual stage
monoecious
both male and female organs: “hermaphrodite”
vs. diocious
protozoan parasites
unicellular, eukaryotic
at least 1 nucleus
motile: cilia, flagella, +/- pseudopodia, sexual/asexual repro
helminths
worms:
nematodes
cestodes
trematodes
nematodes
non-segmented roundworms
cestodes
flat, segmented bodies with head (scolex) and segments (proglattids)
also called tapeworms
trematodes
flukes, nonsegmented flatworms
arthropods
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 ?
for Crypto?
cyst -G
oocyst -C
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
worldwide
G and C seasonality
late summer, early fall
G and C infectious dose?
low!
person-person spread is important (1-1000!!!)
which one (G/C) is an EC pathogen and which is an obligate IC invasive parasite?
Giardia: EC
Crypto: IC
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
Giardia lamblia
2 forms:
flagellated protozoan
2 forms: trophozoite and cyst
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)
Giardia cyst
infectious form
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?
cyst:
can survived in moderately moist cool environments
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
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
Giardia associations
MALES* at higher risk
no seasonality
places: St. Petersburg, New Zealand (waterfalls)
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
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
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
diarrhea
host ingests this form of Giardia via ??
cysts
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
“lawnmower effect”
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
Giardia immunity
secretory IgA Abs
B cell-independent mechanism also: parasite eradication (poorly understood)
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
how long does acute Giardia last?
additional effect?
3-4 days
lose 10 lbs (average)
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
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)
-DFA
-PCR
Giardia tx
quniacrine (anti-protozoal) metronidazole furazolidone albendazole *all have some toxicity/side effects, monitor* *follow-up with stool samples*
furazolidone mech
cross-link DNA, tx diarrhea and enteritis from bac/protozoal inf.
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
Giardia prev/ppx
proper disposal of feces
good personal hygiene
only drinking tx water
Cryptosporidiosis parvum characteristics
stains with??
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
(not Giardia??)
Crypto reservoir?
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
10^8-10^9
Crypto gender, season assoc.
none
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
then ??
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 ??
infects jejunum
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)
cholera-like toxin
Crypto immunity: ??? appear to control replication
TH1 and IgA
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
Crypto presentation:
fever?
stools/day ??
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)
Crypto dx
acid fast oocytes in stool (special order for AF on O&P)
DFA *sn
Ag-capture ELISA
enterotest
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)
Isospora belli actual name…
clinically indistinguishable from ??
Cytoisospora belli
Crypto
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
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
Blastocystis hominid clinically indistinguishable from ??
Crypto
protozoan pathogen, can be carried asymptomatically
most common cause of chronic diarrhea in HIV+ pt??
which are what?
microsporidia
fungal pathogens
most common microsporidia
also most common microsporidian causing enteritis in AIDS pts
Enterocytozoan bieneusi
Enterocytozoan bieneusi
zoonotic obligate IC pathogen (all microspor)
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)
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 survive??
directly human-human
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
AIDS, immunocompromis
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
albendazole
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.
NONE
Cyclospora seasonality
warm and rainy seasons
Cyclospora risk factors
US outbreaks: imported fruit (berries)
Cyclospora oocyst is ?? when passed in stools
different from Crypto
NOT INFECTIVE
therefore, NO fecal-oral transmission
Cyclospora sporulation…
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
Cyclospora immunity
unknown
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
some Cyclospora-inf. ppl are
asymptomatic
if Cyclospora not tx, may last how long ?
few days–>month or longer!
may relapse
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
Cyclospora ddx
Cypto, Giardia
Cyclospora tx
TMP-SMX unlike Crypto
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
how to prev. cyclospora
clean yo fruit!
