Protozoa

20 um

Entamoeba histolytica Trophozoite

12-15 um

Entamoeba histolytica Cyst wet mount saline

12-15 um

Entamoeba histolytica cyst Trichrome

20 um

Entamoeba histolytica Trophozoite wet mount Iodine

Entamoeba histolytica

Only pathogenic intestinal amoeba

Worldwide distribution

“Flask shaped” lesions in intestines - Dysentary

Forms sterile abscesses

Co-infections by bacteria causing GI disease may occur

serological test to differentiate from E. dispar

Entamoeba dispar

Amoeba

Identical to E. histolytica, need serological test

Does not ingest RBCs

Commensal

Entamoeba hartmanni

Amoeba

Identical to E. histolytica

Slightly smaller than E. histolytica

Cysts: 6-8 um

Troph: 8-10 um

Commensal

Entamoeba coli

Largest amoeba

Trophs: up to 50 um, oval, single nucleus with irregular chromatin ring, eccentric karyosome

Cyst: up to 35 um, 5+ nuclei, coarse chromatin ring, splintered chromatoid bar

10-35 um

Entamoeba coli cyst iodine wet mount

15-50 um

Entamoeba coli troph Trichrome

Endolimax nana

Amoeba

Troph has dense karyosome with thin nuclear membrane - “ball and socket”, 6-12 um

Cyst looks like potato with eyes, 4 nuclei, 6-8 um

Reservoir hosts: humans, pigs, primates

6-12 um

Endolimax nana troph Trichrome

Iodamoeba butschlii

Amoeba

commensal

Troph: large dense karyosome, heavier chromatin, “dirty” cytoplasm

Cyst:single nucleus, crescent halo around karyosome, glycogen vacuole

8-20 um

Iodamoeba butschlii Troph Trichrome

5-20 um

Iodamoeba butschlii Cyst

Blastocystis

Pathogenic potential, opportunistic

Risk factors: immunocompromised, poor hygiene, tropical country

Vacuolated form most common: 5-40 um, 90% vacuole, nuclei pushed to periphery

Disease: associated with IBD, self limiting, non-specific

5-40 um

Blastocystis sp. iodine wet mount

5-40 um

Blastocystis sp Trichrome

Amoebae

Pathogenic: Entamoeba histolytica

Commensal: Entamoeba dispar, Entamoeba hartmanni, Entamoeba coli, Endolimax nana, Iodamoeba butschlii

Unknown: Blastocystis

Flagellates

Pathogenic:

Dientamoeba fragilis, Giardia lamblia/intestinalis, Trichomonas vaginalis

Commensal:

Trichomonas hominis, Trichomonas tenax, Chilomastix mesnili

Flagellate Life Cycle

Divide via binary fission

ingestion of cysts in contaminated food/water or from hands

Dientamoeba fraglilis

No external flagellum, looks similar to amoebas

worldwide

occasionally pathogenic, symptoms: colicky pains, fatigue, weight loss

NOT SEEN ON WET PREPS

Trophs: 4-15 um, 20-40% have one nucleus, fragmented karyosome (3-5 granules), no peripheral chromatin, dirty cytoplasm

likes to co-infect with pinworm

4-15 um

Dientamoeba fragilis Trichrome

Giardia lamblia/intestinalis/duodenalis

Most common parasite in USA

Pathogenic, infects upper small intestine, does not invade tissues

Beavers and others are reservoirs, Common in campers

Troph: 10-20 um, 2 nuclei, 2 paranasal bodies, 1 axostyle, 8 flagella, suck onto intestine

Cyst: features of troph inside cyst, may have 4 nuclei, 11-14 um

Giardia Symptoms

Acute:

similar to food poisoning, lasts a few days, gas, foul-smelling stool, watery diarrhea, gray-green color

Chronic:

recurrent brief episodes of loose, foul-smelling, gray, foamy stools