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Sarcocystis hominis
Humans serve as definitive hosts; cattle as intermediate hosts.
Epidemiology:
1) cattle are infected as intermediate hosts from human feces contaminated with sporocysts
Pathology:
1) intestinal infection is acquired by ingestion of raw or incompletely cooked beef that contain tissue cysts (sarcocysts)
2) infection is self-limited because asexual reproduction occurs in intermediate host (cattle)
3) oocyst formation is limited by the number of sarcocysts ingested
Clinical manifestations:
1) generally asymptomatic
2) transient abdominal pain, diarrhea, or anorexia
Laboratory:
1) diagnosis is made by recovery of sporocysts in feces
2) oocysts are thin-walled & often not dectable or ruptured with release of 2 sporocysts
3) sporocysts
a) measure 25 by 30 um
b) each contains 4 sporozoites
c) best seen on wet mount or with acid-fast staining, trichrome stains of little value
d) larger than oocysts of Cryptosporidia
Management: no specific therapy exists
Related
definitive (final) host
intermediate (secondary) host
oocyst
sporocyst
sporozoite
General
Sarcocystis
Properties
KINGDOM: animal
PHYLUM: protozoa
References
- Clinical Diagnosis & Management by Laboratory Methods,
19th edition, J.B. Henry (ed), W.B. Saunders Co., Philadelphia,
PA. 1996, pg 1280
- Stedman's Medical Dictionary 26th ed, Williams &
Wilkins, Baltimore, 1995