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Isospora belli; Cystoisospora belli
Epidemiology:
1) oocysts are passed in feces which mature to infectious sporozoites in the environment
- oocysts in the environment may remain infectious for months
2) human to human fecal-oral transmission
3) no animal reservoir identified
4) infection most common in South America, Africa, and Southeast Asia
Pathology:
1) undergoes both sexual & asexual reproduction in the cytoplasm of epithelial cells in the small intestine
2) sexual reproduction results in production of oocysts which a passed in feces
Clinical manifestations:
1) watery diarrhea (non-bloody)
2) abdominal pain, cramps
2) malabsorption, anorexia, malaise, vomiting, fever
3) generally self-limited, except in patients with AIDS or other immunodeficiency syndromes
Laboratory:
1) Isospora belli in stool
2) diagnosis is made by finding unsporulated oocysts in feces
a) measure 12 by 30 microns
b) infectious oocyst contains 2 sporocysts, each with 4 sporozoites
c) direct wet mount or concentration methods
d) oocysts stain with acid-fast stains
e) ultraviolet autofluorescence microscopy
3) sporulation occurs if feces specimen is left unfixed for 24-48 hours
4) Isospora belli DNA
* images [4]
Management:
1) supportive therapy, fluid & electrolyte replacement
2) Bactrim DS (160/800)
a) 1 PO QID for 10 days, then
b) 1 PO BID for 21 days
3) ciprofloxacin is alternative
4) pyrimethamine 50-75 mg/day
5) maintenance doses may be required to prevent relapses with HIV1 infection
a) Bactrim DS, 1 PO 3 times/week
b) sulfadoxine 500 mg plus pyrimethamine 25 mg weekly
Related
isosporiasis
oocyst
sporozoite
General
Isospora
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
- Harrison's Principles of Internal Medicine, 14th ed.
Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 1194
- Medical Knowledge Self Assessment Program (MKSAP) 11, American
College of Physicians, Philadelphia 1998
- Grimm L
What's Eating You: 12 Common Intestinal Parasites.
Medscape. November 25, 2019
https://reference.medscape.com/slideshow/intestinal-parasites-6010996