Stool Specimen
Parasitology –
Intestinal Sporozoa
• Wet preps (direct and concentrate)
– Saline (look for motility), Iodine
– Scan entire slide on 10x, examine on 40x
• Permanent stained smears
Student Lab
Clinical Laboratory Science Program
Carol Larson MSEd, MT(ASCP)
What to look for
• Size = 4-35 µm
• Shapes
– Round, oval, oblong
– Scan on 40x, examine suspects on 100x
• Modified acid-fast stain
Identify Specific Coccidia
• Isospora (Cystoisospora) belli
• Cryptosporidium parvum
• Cyclospora species
• Key characteristics (structure)
– Cell wall
– Sporant
Isospora belli - Oocyst
Isospora belli - Oocyst
© CDC
© CDC
© CDC
• Shape
– Oval
• Cell wall
– 2 layered, smooth
• Young oocyst
– 1-2 sporoblasts
• Mature oocyst
– 2 sporocysts with 4 sporozoites
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Clinical Significance
Cryptosporidium parvum - Oocyst
• Isosporiasis
• Shape
– Infective form: oocyst
– Human to human transmission only
– Asymptomatic to mild diarrhea
– Opportunistic in immunocompromised
patients
– Roundish
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Cryptosporidium parvum - Oocyst
Yeast
Thick cell wall
No sporocysts
4 sporozoites
1-6 dark granules
Oocysts
Use modified acid-fast stain to diagnose
© CDC
Clinical Significance
• Cryptosporidiosis
– Infective form: oocyst
– Immunocompetent – self-limiting diarrhea
– Immunocompromised patients – watery
diarrhea, dehydration
© CDC
© CDC
© CDC
Cyclospora species - Oocyst
Clinical Significance
• Shape
• Infection with Cyclospora
– Roundish, oval
• Mature oocyst
– 2 sporocysts with
2 sporozoites
© CDC
– Infective form: oocyst
– Human to human transmission only
– Immunocompetent – self-limiting diarrhea
– Immunocompromised patients – prolonged
diarrhea (4-6 weeks)
© CDC
2
Clinical Significance
Size Comparison
• Infection with Microsporidia
– Infective form: spore injects sporoplasm
into host cell
– Immunocompromised patients
– Enteritis, encephalitis, nephritis,
keratoconjunctivitis
Size Comparison
In Summary …
• Specimens
• What to look for
• Key characteristics of intestinal
sporozoa
• Clinical significance
Specimens
Parasitology –
Tissue Sporozoa
Student Lab
Clinical Laboratory Science Program
Carol Larson MSEd, MT(ASCP)
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Serum
Tissue
Bronchial alveolar lavage (BAL)
Diagnosis
– Serological testing
– Histological staining
– Molecular techniques
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Toxoplasma gondii
Toxoplasma gondii
© CDC
• Oocyst
• Tachyzoite
– Shape: oval
– Cell wall: 2 layer
– Sporocysts = 2 with 4
sporozoites
– Shape: crescent-shaped,
more rounded at one end
– Nucleus: 1
– Contains organelles
– Actively multiplying form
© CDC
© CDC
Toxoplasma gondii
Clinical Significance
• Bradyzoite
– Shape: similar to
tachyzoite but smaller
– Many bradyzoites
enclose selves to form
cyst
– Slow growing form
© CDC
• Toxoplasmosis
© CDC
Clinical Significance
• Congenital Toxoplasmosis
– Infective form: organism crosses placenta
– Third trimester – asymptomatic to mild
symptoms
– First & second trimester – severe
symptoms such as stillbirth, CNS
involvement, psychomotor disturbances
– Diagnosis: serological – IgM antibodies
– Infective form: oocyst
– Immunocompetent – asymptomatic or
mimics infectious mononucleosis
– Immunocompromised – may be severe
with various symptoms
– Diagnosis: serological
Clinical Significance
• Immunocompromised Toxoplasmosis
– Disseminated disease from primary
infection or dormant pseudocysts
– Cerebral disease
• Early symptoms – headache, fever, lethargy,
altered mental status
• Later symptoms – neurologic deficits, brain
lesions, convulsions
– Diagnosis: CSF IgG, tachyzoites
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In Summary …
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Specimens
What to look for
Key characteristics of tissue sporozoa
Clinical significance
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