Diarrheagenic Protozoan Flashcards
Acquiring Giardiasis
zoonosis - beaver, dogs, cats, and primates
drinking contaminated drinking water
At risk for giardia
children immoncompromised day care workers backpackers/campers drink shallow well water oral sex travel
What causes giardiasis
G. Lamblia (G. intestinalis)
Most commonly identified intestinal parasite in the world
G. lamblia
G. lamblia description
flagellate protozoan; no intermediate hosts required
Morph stages of g. lamblia
Trophozoite, cyst (infective)
Trophozoite of g. lamblia
exists freely in small intestine; TEAR DROP W/ BILOBED VENTRAL DISCS, FLAGELLA AND 2 NUCLEI; does not invade tissue/RBC; feeds on mucous
Cyst of g. lamblia
form passed into environment;
oval, hyaline wall
4 nuclei when mature
1 cyst = 2 trophozoites
Giardia life cycle:
ingest cyst –> encystation in stomach (acid/enzymes) –> trophozoites (pathogenic) pass into small bowel where they divide quickly (9-12 hrs) –> trophozoites in large bowel encyst in neutral pH and bile –> cyst passed to environment
Epidemiology of Giardiasis
highly contagious
drinking water contaminated w/ feces
Children/developing countries (June-Oct)
Rocky Mountains
Infective dose of g. lmablia
10-25 cysts (>25% = 100% infection rate); 2 week incubation; can be STI
Sx of giardia
Watery Diarrhea (NO BLOOD) Stomach pain/anorexia B12 Deficiency (malabsorption)
Virulence of G. lamblia
ventral disc imprints on intestinal mucosa – damages mucosa by flattening vili (leads to malabsorption)
Dx of g. lamblia
O&P exam/stool sample
ELISA - detects GSA65 (problem: antibodies carried >2 years in humans)
Prognosis of G. lamblia
excellent most pt. asymptomatic and self-limiting weight loss, growth retardation re-infection are possible Mortality rare = dehydration
Protozoan illness that can result in colitis and liver abscess
Amoebiasis
Cause of amoebiasis
E. hysitolytica
Species of entamoeba
many are nonpathogenic; E. histolytica is only one that causes disease; E. dispar is commensal (HIV positive patients)
Causes wide spectrum of illness
E. histolytica (intestinal and extraintestinal)
Morph of E. histolytica
Trophozoite (invasive, pathogenic), cyst (infective)
Trophozoite of E. histlytica
1 nucleus non-flagellated feeds (invades tissue/RBC) pseudopod-forming invasive and pathogenic
Cyst of E. histolytica
round/oval; 4 nuclei
infectious stage
Life cycle of E.histolytica
ingest cyst –> excystation in colon –> forms highly motil trophozoites –> colonizes the mucosa of the colon (encyst and pass in feces OR invade intestinal mucosal barrier and go into bloodstream (dissemination))
Dissemination
E. histolytica invading and going into bloodstream
Epidemiology of Amoebiasis
most prevalent in tropical/subtropical
fecal contamination of watter and food
causes more deaths that any parasite other than malaria and shistosomiasis
reportable disease
High risk for amoebiasis
children pregnant long term steroids malnourished immoncompromised institutionalized oral-anal sex
Incubation period of amoebiasis
SHORT- 10 days (compared to 2 weeks for giardia)
S/sx of Amoebiasis
BLOODY STOOLS fever, vomiting, weight loss Extraintestinal- ulcers (RUQ pain) Death from peritonitis, cardiac failure and exhaution anemia (destroys RBC)
Virulence factors of amoebiasis
“lets form a PAC…LPAC)
lectin - assist w/ adhesion
phospholipases
amoebapore- active peptide released to insert ion channel into host cell lipid struction (lysis host cell)
cystein proteases (degrade mucus/immunity, antibody, complements, cellular matrix)
Dx of amoebiasis
trophozoites or cysts in stool
radiology (extraintestinal)- CT/MRI
ELISA- differentiates E. histolytica from E. dispar
PCR
Tx of amoebiasis
metro/tinidazole + iodoquinol
may need surgical repair of abscesses
Non medical tx of amoebiasis
purified water (cysts resistant to Chlorine!!!!) - boiling, iodine, bottled
Resistant to chlorine
amoebiasis
non-bloody, watery stools
Giardia
Cryptosporidiosis cause
at least 15 species (hominis and parvum)
hominis- humans only
parvum- bovine and humans
Prognosis of cyrpto
self-limiting in healthy
serious in immunocompromised (aids)
Morph of Cryptosporidium
oocysts & sporozoites
Oocysts of crypto
contain 4 sporozoites; infectious stage; does not multiply outside of host; asexual and sexual reproduction in host (sexual = evolution)
Sporozoites
motile
bind receptors on surface of intestinal epithelial cells
life cycle of crypto
ingest oocytes –> activated to release 4 infective sporozoites –> bind receptors on intestinal epithelial cells –> ingested into parasitophorous vacuole –> inside epithelial cell, parasite undergoes sexual/asexual reproduction to form more oocysts (thin/thick walled oocysts) –> oocyst shedding
Thin walled oocysts
asexual; lead to reinfection of host
Thick walled oocysts
sexual; shed into environment
auto-infection possible
crypto (thin-walled)
Parasitophorous vacuole
produced by crypto; near surface of epithelial cell, separated from cytoplasm by dense layer; protects crypto
2 nuclei, flagella
giardia
parasitophorous vacuole
crypto
1 nuclei, no flagella
amoebiasis
Epidemiology of crypto
fecal-oral contamination
sporadic cases from contaminated water/food – cows, recreational water (prevalent in swimmers/pools)
Associated with AIDS
developing countries
People most likely to get crypto
AIDS, swimmers, work w/ cows
Pathophys of crypto
highly infectious (10 oocysts; infective immediatly after excretion)
5-10 incubation
infection difficult to treat (vacuoles)
Infection: due to increased intestinal permeability, chloride secretion and malabsorption
Sx of crypto
WATERY DIARRHEA
patient severely wasted
lasts ~2 weeks (self-limiting in immunocompetant)
Immunocompromised: bad prognosis if CD4 low, pancreatitis, severe weight loss
Dx of crypto
oocysts in stool (zinc sulfate centrifugal flotation), IMMUNOFLUORESCENCE, acid fast oocysts are round, ELISA
small, oval and acid fast
Crypto
Linked to patients in latin america
cyclosporiasis
Cause of cyclosporiasis
cyclospora cayetanensis
Autofluorescent oocyst
Cyclosporiasis (much larger oocysts than crypto)
how do you get cyclospora?
ingest oocyst in contaminated water and imported foods (fresh fruit and veggies)
Life cycle of cyclospora
ingest oocyst –> similar progression;
resistant to chlorine
Oocysts shed in feces: MUST SPORULATE IN THE ENVIRONMENT (days– reinfection rare)
Resistant to chlorine
Cryptosporidium, cyclospora
Presentation of cyclospora
EXPLOSIVE, non-blood watery diarrhea
Dx of cyclospora
Large oocyst in stool samle (difficult due to low #’s in stool, may have to repeat several days); ACID FAST POSITIVE, AUTOFLOURESCENT OOCYTE;
PCR
Blastocystis hominis
polymorphic; ingest cyst from contaminated food/water (animal feces); LARGE CENTRAL VACUOLE, MULTIPLE NUECLEI AROUND RIM
Balantidium Coli
large intestine microbe (zoonotic: pigs);
can result in GUT PERFORATION
Tropho and cyst forms: contains MACRONUCLEUS;
cilia evident on trophozoite
