Primate Intestinal Protozoan Parasitology

Entamoeba histolytica

Cysts:

• Size: 10-20µm spherical (typically 12-15µm)

• Nucleus: 1, 4 and occasionally 8, 1N >5µm, 2N ~ 3.5 - 5µm, 4N ~ 2 - 2.5µm

• Chromatin: fine, uniform

• Karyosome: small, central

• Cytoplasm: rounded or oval chromatoidal bars

Trophozoites:

• Size: 12-60µm

• Nucleus: 1, ~3.5 - 5µm

• Chromatin: fine, uniform

• Karyosome: small, round and central

• Cytoplasm: ground glass clean appearance • Inclusions: RBC’s

• Pathogenic

Entamoeba hartmanni

Cysts:

• Size: 5-10µm

• Nucleus: 1, 2 or 4 (2 are common), 4N ~1.5-2.5µm

• Chromatin: even distribution

• Karyosome: centrally located, small and compact

• Cytoplasm: fine granular, chromatoid bodies are “cigar” shaped

Trophozoites:

• Size: 5-12µm

• Nucleus: 1, ~2 - 2.5µm

• Chromatin: fine and even

• Karyosome: small, eccentric or centrally located

• Cytoplasm: fine granular appearance

• Non-pathogenic

Entamoeba coli

Cyst:

• Size: 10-35µm, spherical

• Nucleus: 2-8 nuclei, 2N ~ ≥8µm, 4N ~ 5 - 6µm, 8N ~ 2.5 - 3µm

• Chromatin: uneven

• Karyosome: large, eccentric

• Cytoplasm: splinter shaped chromatoid bars, sometimes large vacuoles

Trophozoites:

• Size: 15-50µm

• Nucleus: 1, ~3.0-4.5µm

• Chromatin: irregular and uneven

Nebulous Border “Floppy Pancake”

• Karyosome: large, off centered

• Cytoplasm: course and often with large food vacuoles. Can see RBC’s and WBC’s as well as yeast

• Non-pathogenic

Entamoeba chattoni/E. polecki

Cyst:

• Size: 5-20µm

• Nucleus: 1 large circular (occasionally 2), ~ 5 - 8µm

• Chromatin: fine and even

• Karyosome: small and central, may not be visible

• Cytoplasm: granular, often will contain several small chromatoid bodies

Trophozoite:

• Size: 10-30µm

• Nucleus: 1, ~2.5-3.5µm

• Chromatin: fine and even

• Karyosome: small, and central, may be absent

• Cytoplasm: granular

Blastocystis

• Unique protozoan

• Pleomorphic features

• Controversial pathological effects

• Size: 2-200µm, with a thin outer shell of cytoplasm

• Nucleus: 1 or more (usually 2)

• Inner vacuole with storage droplet

Iodamoeba buetschlii

Cyst:

• Size: 5-20µm, ovoid

• Nucleus: 1, elliptical

• Achromatic granules

• Karyosome large (if present)

• Cytoplasm: almost always has a glycogen vacuole

Trophozoite:

• Size: 8-20µm

• Nucleus: 1, ~2.5-3.0µm

• Chromatin: fine, granular, “fuzzy” appearance

• Karyosome: large

• Cytoplasm: fine, granular with small food vacuoles

Endolimax nana

Cyst:

• Size: 8-15µm, usually ovoid

• Nucleus: 4

• Chromatin: thin to none

• Karyosome: large

• Cytoplasm: granular with a large vacuole and a few thin chromatoid bodies

Trophozoite:

• Size: 5-15µm

• Nucleus: 1, ~1.5-2.5µm

• Chromatin: thin

• Karyosome: large

• Cytoplasm: granular

• Non-pathogenic

Balantidium coli

Cyst:

• Size: 40-65µm

• Nucleus: 1 Macronucleus

• Cilia visible under cyst wall in young forms

Trophozoite:

• Size: 50-100µm, spheroid to pear shaped

• Large bar shaped or dumbbell shaped macronucleus

• Micronucleus may be obscured

• Prominent oral groove and cytopyge

Chilomastix mesnili

Cyst:

• Size: 6-10µm, lemon shaped with “knob”

• Nucleus: 1 (not distinct) • Cytoplasm: contain curved fibers

Trophozoite:

• Size: 5-20µm, pear shaped with tail

• Nucleus: 1, ~1.5-3.5µm

• Karyosome: small and variable

• Chromatin: can be solid, diffuse or fragmented

• Cytoplasm: course with large food vacuole

• Non-pathogenic

“Swimming Tuna”

Pentatrichomonas hominis

• Size: 5-15µm

• Nucleus: 1, ~1.5-2.5µm

• Cytoplasm: smooth to fine granular, undulating membrane is often visible

“Smiling Whale”

Dientamoeba fragalis

• Size: 5-25µm

• Nucleus: 1 - 2, ~1.5-2µm often bi-nucleated.

• Karyosome: is fragmented into small granules in stained preps

• Cytoplasm: pale staining with numerous small food vacuoles

Enteromonas hominis

Cyst:

• Size: 4-8µm, ovoid

• Nucleus: 2 or 4 bipolar

Trophozoite:

• Size: 4-10µm

• Nucleus: 1, ~0.7-1.5µm, tiny and usually pushed up against on end of the cell (resembles a small E. hartmanni or Endolimax nucleus)

• Cytoplasm: smooth with a large glycogen vacuole

Retortamonas intestinalis

Cyst:

• Size: 4-8µm, ovoid

• Nucleus: 1

• Characteristic “knob”, resembles a very small Chilomastix cyst

Trophozoite:

• Size: 4-10µm

• Nucleus: 1, ~0.7-1.5µm, tiny and usually pushed up against on end of the cell (resembles a small E. hartmanni or Endolimax nucleus)

• Cytoplasm: smooth with a large glycogen vacuole

Giardia

Cyst:

• Size: 8-15µm

• Nucleus: 2-4 usually located on one end

• Karyosome: central

• Cytoplasm: contains median bodies and flagella

Trophozoite:

• Size: 10-20µm

• Nucleus: 2, ~1.5-2.0µm

• Karyosome: central

• Cytoplasm: large central sucker disc with 8 flagella

• Pathogenic

Cryptosporidium

• Size: 4-6µm

• Thin walled, spherical to oval shape

• 4 sporozoites

Cyclospora cayetanensis

• Size: 8-10µm

• Thin walled, spherical

• Single sporoblast containing several refractile bodies when passed

• 2 sporocysts with 2 sporozoites

Cystioisospora (Isospora) belli

• Size:20-30µm

• Thin walled, ovoid with tapered ends

• Mature oocysts contain 2 sporocysts with 4 sporozoites each

Sarcocystis

• Size:10-15µm

• Infection from eating muscle of intermediate host

• Usually not pathogenic in definitive host

Microsoporidia

• Size: 3-6µm long depending on species

• Spores can be ovoid, spheroid or cylindrical

• Trilaminar spore wall is visible by electron microscopy

• Contains infective sporoplasm and coiled polar tube with accessory structures to allow it to emerge rapidly and infect a host cell

• Some are facultative parasites in immunosuppressed animals-Enterocytozoon bieneusi

• Encephalitozoon intestinalis, various Nosema and Pleistophora species can cause severe diarrhea

• Difficult to detect without proper staining