Protozoans

INFECTIVE SPECIMEN OF DISEASE

PROTOZOA CHARACTERISTICS MAIN HABITAT MOTILITY DRUG OF CHOICE
STAGE CHOICE ASSOCIATED
AmoeBOID
Trophozoites:
Size range: 8-65 µm
Pseudopod: Finger-like
Number of nuclei: One
Karyosome: Small and central
Peripheral chromatin: Fine and
evenly distributed
Cytoplasm: Finely granular
Cytoplasmic inclusions: Ingested red - Paromomycin,
- Stool - Intestinal amebiasis
blood cells diloxanide furoate
Intestinal tract; may - Sigmoidoscopy - Amebic colitis
Entamoeba Active progression in (Furamide)
disseminate to the Cyst specimens - Amebic dysentery
histolytica CYST: liver
definite direction
- Hepatic abscess - Extraintestinal
- Metronidazole
Size range: 8-22 µm (Flagyl)
material amebiasis
Shape: Spherical to round - Iodoquinol
Number of nuclei: One to four
Karyosome: Small and central
Peripheral chromatin Fine and evenly
distributed
Cytoplasm Finely granular
Cytoplasmic inclusions In young
cysts, chromatoid bars, rounded
ends; & diffuse glycogen mass
TROPHOZOITE:
Size range: 5-15 µm - Intestinal amebiasis
Number of nuclei: One - Stool - Amebic colitis
Entamoeba Pseudopod: Finger-like Intestinal tract Cyst - Sigmoidoscopy - Amebic dysentery No treatment indicated
hartmanni Karyosome: Small and central Nonprogressive
specimens - Extraintestinal
Peripheral chromatin: Fine and amebiasis
evenly distributed
Cytoplasm: Finely granular

A.B.YSAIS
 Cytoplasmic inclusions: Ingested
bacteria may be present

CYST:
Size range: 5-12 µm
Shape: Spherical
Number of nuclei: One to four
Karyosome: Small and central
Peripheral chromatin: Fine and
evenly distributed
Cytoplasm: Finely granular
Cytoplasmic inclusions: In young
cysts, chromatoid bars, rounded
ends; & diffuse glycogen mass
Trophozoites:
Size range: 12-55 µm
Pseudopod: Blunt
Number of nuclei: One
Karyosome: Large, irregular shape,
eccentric
Peripheral chromatin: Unevenly
distributed
Cytoplasm: Coarse and granulated
Cytoplasmic inclusions: Vacuoles
containing bacteria often visible - Intestinal amebiasis
- Stool - Amebic colitis
Sluggish, usually
Entamoeba coli Intestinal tract Cyst - Sigmoidoscopy - Amebic dysentery No treatment indicated
CYST: nonprogressive
specimens - Extraintestinal
Size range: 8-35 µm amebiasis
Shape: Round to spherical
Number of nuclei: One to eight
Karyosome: Large, irregular shape,
eccentric
Peripheral chromatin: Unevenly
distributed
Cytoplasm: Coarse and granulated
Cytoplasmic inclusions:
- Diffuse glycogen mass present
in young cysts; may displace nuclei

A.B.YSAIS
 (often seen in cysts with two
nuclei) to opposite ends of the
cyst
- Thin chromatoid bars with
pointed to splintered ends in young
cysts
Trophozoites:
Size range: 8-25 µm
Pseudopod:
Number of nuclei: One
Karyosome: Small and central
Peripheral chromatin: Fine and
evenly distributed
Cytoplasm: Granular and vacuolated
IN NORMAL
Cytoplasmic inclusions: Ingested
bacteria, & other food particles STOOLS:
Sluggish, - Paromomycin,
nonprogressive diloxanide furoate
Entamoeba CYST: Intestinal tract Cyst - Stool None (Furamide)
polecki Size range: 10-20 µm
IN DIARRHEAL - Metronidazole
Shape: Spherical or oval (Flagyl)
Number of nuclei: One STOOLS:
Karyosome: Small and central Progressive,
Peripheral chromatin: Fine and unidirectional
evenly distributed
Cytoplasm: Granular
Cytoplasmic inclusions:
- In young cysts, chromatoid bars,
angular or pointed end; & glycogen
mass
- Inclusion mass
Trophozoites:
Size range: 5-12 µm
Pseudopod: Blunt
Number of nuclei: One - Stool
Sluggish, moderately
Endolimax nana Karyosome: Large, irregular, blotlike Intestinal tract Cyst - Sigmoidoscopy None No treatment indicated
progressive
Peripheral chromatin: Absent specimens
Cytoplasm: Granular and vacuolated
Cytoplasmic inclusion: Bacteria

A.B.YSAIS
 CYST:
Size range: 4-12 µm
Shape: Spherical, ovoid, ellipsoid
Number of nuclei: One to four; four
most common
Karyosome: Large, blotlike, usually
central
Peripheral chromatin: Absent
Cytoplasm: Granular and vacuolated
Cytoplasmic inclusions:
- Chromatin granules
- Nondescript small mass
- Diffuse glycogen mass in young
cysts
Trophozoites:
Size range: 8-22 µm
Pseudopod:
Number of nuclei: One
Karyosome: Large, usually central
refractive achromatic granules may
or may not be present
Peripheral chromatin: Absent
Cytoplasm: Coarsely granular and
vacuolated
Cytoplasmic inclusions: Bacteria,
- Stool
Iodamoeba yeast cells, & other debris Sluggish, slightly
Intestinal tract Cyst - Sigmoidoscopy None No treatment indicated
bütschlii progressive
specimens
CYST:
Size range: 5-22 µm
Shape: Ovoid, ellipsoid, triangular,
other shapes
Number of nuclei: One
Karyosome: Large, eccentric
achromatic granules on one side
may be present
Peripheral chromatin: Absent
Cytoplasm: Coarsely granular and
vacuolated

A.B.YSAIS
 Cytoplasmic inclusions: Well-defined
glycogen mass; & granules may be
present
Trophozoites:
Size range: 8-20 µm
Pseudopod: Varying appearance
Number of nuclei: One
Karyosome: Centrally located
Peripheral chromatin: Fine and
Entamoeba Moderately active,
evenly distributed Mouth Trophozoite Mouth scrapings None No treatment indicated
gingivalis progressive
Cytoplasm: Finely granular
Cytoplasmic inclusions: Leukocytes,
epithelial cells, & bacteria

CYST:
No cyst stage
Trophozoites:
Size range: 8-22 µm
Pseudopod: Blunt
Number of nuclei: One
Karyosome: Large and usually
centrally located
Peripheral chromatin: Absent
Cytoplasm: Granular, usually
vacuolated Primary amebic - Amphotericin B
Naegleria
CNS Trophozoite Sluglike - CSF meningoencephalitis - Miconazole
fowleri
CYST: (PAM) - Rifampin
Size range: 9 to 12 µm
Shape: Generally round and have
thick cell walls
Number of nuclei: One
Karyosome: Large, centrally located
Peripheral chromatin: Absent
Cytoplasm: Typically granular, and
often contains vacuoles
Trophozoites: - CSF - Granulomatous - Sulfamethazine
Acanthamoeba spp. Size range: 12-45 µm CNS, eye Trophozoite Sluggish - Brain tissue amebic encephalitis - Itraconazole
Pseudopods: Spinelike - Corneal scrapings (GAE) - Ketoconazole

A.B.YSAIS
 Number of nuclei: One - Acanthamoeba - Miconazole
Karyosome: Large keratitis - Propamidine
Peripheral chromatin: Absent isethionate
Cytoplasm: Granular and vacuolated - Rifampin

CYST:
Size range: 8-25 µm
Shape: Roundish with ragged edges
Number of nuclei: One
Karyosome: Large and central
Peripheral chromatin: Absent
Cytoplasm: Disorganized, granular,
sometimes vacuolated
Other features: Double cell wall—
smooth inner cell wall and outer
jagged cell wall
FLAGELLATES
Trophozoites:
Size range: 8-20 µm long, 5-16
µm wide
Shape: Pear-shaped, teardrop
Appearance: Bilaterally symmetrical
Nuclei: Two ovoid-shaped, each with
a large karyosome; no peripheral
chromatin
Giardia
Flagella: Four pairs, origination of - Metronidazole
intestinalis
each: (Flagyl)
a.k.a. - Giardiasis
- One pair, anterior end Intestinal tract Cyst Falling leaf - Stool - Tinidazole
Giardia lamblia - Traveler’s diarrhea
- One pair, posterior end (Tindamax)
or Giardia
- Two pair, central, extending - Nitazoxanide (Alinia)
duodenale
laterally
Other structures: Two median
bodies; two axonemes; sucking disk

CYST:
Size range: 8-17 µm long, 6-10 µm
wide
Shape: Ovoid

A.B.YSAIS
 Nuclei: Immature cyst, two; mature
cyst, four; central karyosomes; no
peripheral chromatin
Cytoplasm: Retracted from cell wall
Other structures:
- Median bodies: two in immature
cyst or four in fully mature cyst
- Interior flagellar structures:
Twice as many in mature cyst as
compared with immature cyst
Trophozoites:
Size range: 5-25 µm long, 5-10
µm wide
Shape: Pear-shaped
Nuclei: One with small central or
eccentric karyosome; no peripheral
chromatin
Flagella: Four
- Three extending from anterior
end
- One extending posteriorly from
cytostome region
Chilomastix Other structures: Prominent Stiff, rotary,
Intestinal tract Cyst - Stool None No treatment indicated
mesnili cytostome extending 1/3 to 1/2 directional
body length; spiral groove

CYST:
Size range: 5-10 µm long
Shape: Lemon-shaped, with a clear
hyaline knob extending from the
anterior end
Nuclei: One, with large central
karyosome; no peripheral chromatin
Other structures: Well-defined
cytostome located on one side of
the nucleus
- Dientamoeba fragilis
Dientamoeba Trophozoites: Intestinal tract Trophozoite Active, progressive - Stool infection
- Iodoquinol
fragilis Size range: 5-18 µm (symptomatic)
- Tetracycline

A.B.YSAIS
 Shape: Irregularly round - Paromomycin
Pseudopod: Broad, hyaline (Humatin)
Number of nuclei: Two, each
consisting of massed clumps of
four to eight chromatin granules;
no peripheral chromatin
Cytoplasm: Bacteria-filled vacuoles
common

CYST:
No cyst stage
Trophozoites:
Size range: 7-20 µm long, 5-18
µm wide
Shape: Pear-shaped
Nuclei: One, with a small central
karyosome, no peripheral chromatin
Flagella: Three to five anterior; one
posterior extending from the
Pentatrichomonas posterior end of the undulating
(Trichomonas) membrane Intestinal tract Trophozoite Nervous, jerky - Stool None No treatment indicated
hominis Other features: Axostyle that
extends beyond the posterior end of
the body; full body length undulating
membrane; conical cytostome cleft
in anterior region ventrally located
opposite the undulating membrane

CYST:
No cyst stage
Trophozoites:
Size range: 3-10 µm long, 3-7 µm
wide
Enteromonas Shape: Oval; sometimes half-circle Intestinal tract Cyst Jerky - Stool None No treatment indicated
hominis Nuclei: One with central karyosome;
no peripheral chromatin
Flagella: Four total
- Three directed anteriorly

A.B.YSAIS
 - One directed posteriorly
Other structures: None

CYST:
Size range: 3-10 µm long, 4-7 µm
wide
Shape: Oval, elongated
Nuclei: One to four; binucleated and
quadrinucleated nuclei located at
opposite ends; central karyosome;
no peripheral chromatin
Other structures: None
Trophozoites:
Size range: 3-7 µm long, 5-6 µm
wide
Shape: Ovoid
Nuclei: One, with small central
karyosome; ring of chromatin
granules may be on nuclear
membrane
Flagella: Two; anterior
Other structures: Cytostome
extending halfway down body length
with well-defined fibril border
Retortamonas
opposite the nucleus in the anterior Intestinal tract Cyst Jerky - Stool None No treatment indicated
intestinalis
end

CYST:
Size range: 3-9 µm long; up to 5
µm wide
Shape: Lemon-shaped, pear-shaped
Nuclei: One, located in anterior-
central region with central
karyosome; may be surrounded by a
delicate ring of chromatin granules
Other structures: Two fused fibrils
resembling a bird’s beak in the

A.B.YSAIS
 anterior nuclear region, only visible
in stained preparations
Trophozoites:
Size range: 5-14 µm long
Shape: Oval, pear-shaped
Nuclei: One, ovoid nucleus; consists
of vesicular region filled with
chromatin granules
Flagella: Five total, all originating
anteriorly: four extend anteriorly
one extends posteriorly
Trichomonas Other structures: - Proper oral hygiene
Mouth Trophozoite Rapid, jerky - Mouth scrapings None
tenax - Undulating membrane extending practice
two thirds of body length with
accompanying costa
- Thick axostyle curves around
nucleus; extends beyond body length
- Small anterior cytostome
opposite undulating membrane

CYST:
No cyst stage
Trophozoites:
Size range: Up to 30 µm long
Shape: Ovoid, round or pear-shaped
Nuclei: One, ovoid, nondescript
Flagella: All originating anteriorly:
three to five extending anteriorly;
one extending posteriorly - Urine - Persistent urethritis
Trichomonas Other features: Urinary tract; genital - Vaginal secretions - Persistent vaginitis - Metronidazole
Trophozoite Rapid, jerky
vaginalis - Undulating membrane extending system - Urethral discharges - Infant Trichomonas (Flagyl)
half of body length - Prostatic fluid, vaginalis infection
- Prominent axostyle that often
curves around nucleus; granules
may be seen along axostyle

CYST:
No cyst stage

A.B.YSAIS
 CILIATES
Trophozoites:
Size range: 28-152 µm in length,
22-123 µm wide
Number of nuclei: Two; kidney-
shaped macronucleus; small spherical
micronucleus
Other features: One or two visible
contractile vacuoles; cytoplasm may
contain food vacuoles and/or
bacteria; small cytostome present;
layer of cilia around organism

CYST: - Oxytetracycline
Size range: 43-66 µm N (Terramycin)
Balantidium coli Number and appearance of nuclei: Intestinal tract Cyst Rotary, boring - Stool - Balantidiasis - Iodoquinol
Two; kidney-shaped macronucleus - Metronidazole
usually present; small spherical (Flagyl)
micronucleus; may not be
observable
Other features: One or two visible
contractile vacuoles in young cysts;
double cyst wall; row of cilia visible
in between cyst wall layers of
young cysts

* Mature cysts typically only reveal

macronucleus on examination. The
other structures are usually not
apparent.
SPOROZOANS
- Chloroquine
- Benign tertian
- Hydroxychloroquine
Plasmodium vivax Schüffner’s dots Liver Sporozoites Gliding motility - Blood malaria
- Primaquine
- Vivax malaria
- Combination therapy
- Benign tertian - Chloroquine
Plasmodium ovale James’ dots Blood Sporozoites Gliding motility - Blood
malaria - Hydroxychloroquine

A.B.YSAIS
 - Ovale malaria - Primaquine
Plasmodium - Quartan malaria - Chloroquine
Ziemann’s dots Blood Sporozoites Gliding motility - Blood
malariae - Malarial malaria - Hydroxychloroquine
- Black water fever
- Malignant tertian
Blood; capillaries of malaria - Chloroquine
Plasmodium
Maurer’s dots deep tissues (spleen, Sporozoites Gliding motility - Blood - Aestivoautumnal - Hydroxychloroquine
falciparum
liver, bone marrow) malaria - Combination therapy
- Subtertian malaria
- Falciparum malaria
Plasmodium - Chloroquine
Sinton and Mulligan’s Stippling Blood Sporozoites Gliding motility - Blood - Simian malaria
knowlesi - Hydroxychloroquine
TROPHOZOITE:
Appearance: Resembles a ring
form; does not contain Schüffner’s, - Clindamycin and
Ziemann’s, or Maurer’s dots quinine
Ring characteristics when stained - Atovaquone and
with Giemsa: Blue cytoplasmic circle azithromycin
connected with or to red chromatin - Diminazene and
Babesia microti, Blood Sporozoite Gliding motility - Blood - Babesiosis
dot; vacuole usually present pentamidine, in
combination or singly
MEROZOITE: - Pyrimethamine and
Appearance: Resembles four quinine, in combination
trophozoites attached by their or singly
respective chromatin dots in the
shape of a Maltese cross
TROPHOZOITE:
Appearance: Resembles a ring - Clindamycin and
form; does not contain Schüffner’s, quinine
Ziemann’s, or Maurer’s dots - Atovaquone and
Ring characteristics when stained azithromycin
with Giemsa: Blue cytoplasmic circle - Diminazene and
Babesia divergens Blood Sporozoite Gliding motility - Blood - Babesiosis
connected with or to red chromatin pentamidine, in
dot; vacuole usually present combination or singly
- Pyrimethamine and
MEROZOITE: quinine, in combination
Appearance: Resembles four or singly
trophozoites attached by their
A.B.YSAIS
 respective chromatin dots in the
shape of a Maltese cross

OOCYST:
Size range: 25-35 µm long, 10-15
µm wide
Appearance: Transparent - Chemotherapy,
Shape: Oval consisting of a
Cell wall: Two layered, colorless and combination of
Isospora belli smooth Intestinal tract Mature oocyst --- - Stool - Isosporiasis trimethoprim and
Developing sporoblast: Unicellular sulfamethoxazole or
with granular cytoplasm pyrimethamine and
Young oocyst: Two sporoblasts sulfadiazin
Mature oocyst: Two sporocysts,
each containing four sausage-shaped
sporozoites
OOCYST:
Shape: Oval
Appearance: Transparent
Number of sporocysts: Two
Size of each sporocyst: 10-18 µm - Chemotherapy,
long consisting of a
Contents of each sporocyst: Four combination of
Sarcocystis - Sarcocystis
sausage-shaped sporozoites --- --- --- - Stool trimethoprim and
species infection
Oocyst cell wall appearance: Clear, sulfamethoxazole or
colorless, double layered pyrimethamine and
sulfadiazin
* In many cases, only single or
double sporocysts cemented
together may be visible in stool
samples.
Cryptosporidium OOCYST: Intestinal tract; can
parvum Size: 4-6 µm disseminate to other Mature oocyst Gliding motility - Stool - Cryptosporidosis - Spiramycin
Shape: Roundish tissues in

A.B.YSAIS
 Number of sporocysts: None compromised host
Number of sporozoites: Four (small) (lung, gallbladder)
Other features: Thick cell wall; one
to six dark granules may be visible
Tachyzoites:
General comment: Actively
multiplying morphologic form
Size: 3-7 × 2-4 µm
Shape: Crescent-shaped, often
more rounded on one end
Number of nuclei: One
Other features: Contains a variety - Trisulfapyrimidines
of organelles that are not readily and pyrimethamine
- Toxoplasmosis
visible (Daraprim)
- Congenital
Toxoplasma Eye; CNS in - Biopsies (any tissue) - Spiramycin
--- Gliding motility toxoplasmosis
gondii Bradyzoites: compromised patient - CSF
- Cerebral
- Corticosteroids
General comment: Slow-growing - Folinic acid
toxoplasmosis
morphologic form (leucovorin)
Size: Smaller than tachyzoites - Atovaquone
Physical appearance: Similar to that
of the tachyzoites
Other features: Hundreds to
thousands of bradyzoites enclose
themselves to form a cyst that
may measure 12-100 µm in
diameter

REFERENCES:
Brown, H., & Neva, F. (1994). Basic Clinical Parasitology (6th Ed.).
Rodak, B. (2013). Hematology: Clinical Principles and Applications (4th Ed.).
Tille, P. (2014). Bailey & Scott's Diagnostic Microbiology (13th Ed.).
Wiser, M. (2011). Protozoa and Human Disease.
Zeibig, E. (2013). Clinical Parasitology: A Practical Approach (2nd Ed.).
www.cdc. gov

A.B.YSAIS