Parasitology 6 Amoebae (Protozoan Diarrhea)

Acute vs Chronic Diarrhea

• Bloody vs. Non-bloody

• Acute is exact onset relative to exposure

• Chronic can be related to underlying factors

Stool O&P Tests

looking for ova (eggs) shed by adult worms and parasites

Encystment

Trophozoite to cyst

Excystation

Cyst to trophozoite

Amoebiasis

• most at risk

• associated with what

• males, hispanics, asian/pacific islanders, > 75 years old

• HIV infection

Entamoeba histolytica

• resides in what organ?

• reservoir?

• transmission type?

• invasive/pathogenic?

• distribution?

• other associations?

• colon

• humans

• fecal-oral

• invasive/pathogenic

• worldwide

• major cause of death in children worldwide

Is Entamoeba dispar pathogenic?

No

If you see erythrophagocytosis, what is that a likely indicator of?

Entamoeba dispar

Asymptomatic infection amebiasis is called what? caused by which species?

Luminal amebiasis

• E. dispar

Intestinal amebiasis symptoms

• ulcerous colitis

• appendicitis

• toxic megacolon

• amebomas

Extraintestinal amebiasis symptoms

• liver abscess and peritonitis

• pleuropulmonary abscess

• cutaneous and genital amebic lesions

• brain hemorrhages

In amebic abscess of liver, what can you find?

trophozoites

Diagnosis of Amebiasis (trying to SEE the parasites)

• 3x stool exam

• stool wet mounts and permanent stains

• concentration techniques (for cysts)

• biopsy (for trophozoites)

• liver scan, CT scan, ultrasound

Trophozoite of E. histo/dispar

• found in what

• structure?

• what does it look like

• in diarrheal stool

• can be elongated

• single nucleus w/ central karyosome and peripheral chromatin

• ground glass cytoplasm

Cyst for E. histo/dispar

• found in what

• what does it look like

• 1 cyst gives how many trophozoites?

• in formed stool

• four nuclei and chromatoidal body

• 1 cyst gives 4 trophozoites

Diagnosis for Amebiasis (if you cannot see them)

• Fecal antigen EIA

• multiplex PCR

• serology (EIA antibody)

  • highly specific, but cannot differentiate past/new infxn

Which is more frequent: E. histolytica or E. dispar?

E. dispar is 10x more frequent

Why is E. dispar non-pathogenic?

It is non-invasive, in contrast to E. histolytica

How can you distinguish E. histo/dispar?

isoenzymatic, immunologic, or molecular assays

What method does NOT work to prevent amebiasis?

Chlorination

Cyst

• 8 nuclei

• eccentric karyosome

• 10-35 micron

Trophozoite

• 1 nucleus

• eccentric, large karyosome

• dirty/vacuolated cytoplasm

• 15-50 micron

Entamoeba coli

Cyst

• smaller, but like E. histo

• Diffuse glycogen

• 5-10 micron

Trophozoite

• small, compact karyosome

• 5-15 micron

Entamoeba hartmanni

Cyst

• Spherical with 4 nuclei

• lacks chromatin bodies

• 5-10 micron

Trophozoite

• single nucleus

• irregular karyosome

• highly vacuolated

• 6-12 micron

Endolimax nana

Cyst

• single nucleus

• large, glycogen vacuole

• 5-20 micron

Trophozoite

• sluggish

• large, central karyosome

• vacuolated, achromatic vacuoles

• 8-20 micron

Iodamoeba buetschlii

Trophozoite ONLY

• 2 nuclei

• inclusions possible

Dientamoeba fragilis

Cyst

• many small chromatid bodies with angular/pointed ends

Trophozoite

Entamoeba polecki

Prevention of Amebiasis

• handwashing

• washing fruits/veggies with detergents

• role as a STD

• water treatment (boiling and iodination)

  • NO CHLORINATION

Treatment for Amebiasis (Asymptomatic vs Symptomatic)

Asymptomatic

• Iodoquinol

• Paromomycin

• Diloxanide furoate

Symptomatic

• Metronidazole first, then the medications above

Balantidium coli

• organ?

• reservoir?

• transmission method?

• movement method?

• distribution?

• symptoms?

• other traits?

• colon

• pigs, not common in humans

• fecal-oral

• cilia

• subtropics/tropics

• colonic ulcers, abscesses (rarely)

• responds to tetracycline

• shifts from cyst to trophozoite back and forth

• 40-200 micron

• cilia on surface

• cystome

• bean-shaped macronucleus

• cysts not seen often

Balantidium coli

T/F: Non-pathogenic amoebae are a sign of fecal-oral contamination

True

E. dispar

What is this trophozoite of?

Entamoeba histolytica

blunt chromatid bar

Entamoeba histolytica

A pointed chromatid bar is a property of which organism?

Entamoeba coli

Life cycle of amebiasis

Mature cysts get ingested and turn into trophozoites in the gut

Trophozoites multiply or turn into cysts

Cysts and trophozoites exit in host feces

When treating symptomatic amebiasis, what medication is to be used first?

Metronidazole

Giardia

• organ

• reservoir

• transmission method

• pathogenic or non?

• small intestine

• human

• fecal-oral

• non-pathogenic

Clinical clues for E. histo

Blood/mucus in stool

Clinical clues for B. coli

Blood/mucus in stool

Clinical clues for Giardia

High volume fatty stools

E. histo, B. coli, and Giardia all get diagnosed with O&P tests, but E. histo also does what?

Serology

E. histo and B. coli reside in the colon, while Giardia resides in

the small intestine

Between E. histo, B. coli, and Giardia, which is extra-intestinal invasive?

E. histo

B. coli is rarely

E. histo complications

perforation, abscess, EI

B. coli complicatiosn

perforation

Giardia complications

malabsorption, poor growth