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Isosporiasis

Oocyst of Isospora belli
This page is about clinical aspects of the disease.  For microbiologic aspects of the causative organism(s), see Cystoisospora belli.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]

Synonyms and keywords: Isospora infection; cystoisoporiasis

Overview

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

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Overview

Isosporiasis is a human intestinal disease caused by a parasite called Isospora belli.

Causes

The coccidian parasite, Isospora belli, infects the epithelial cells of the small intestine, and is the least common of the three intestinal coccidia that infect humans.

Epidemiology and Demographics

Worldwide, especially in tropical and subtropical areas. Infection occurs in immunodepressed individuals, and outbreaks have been reported in institutionalized groups in the United States.

Treatment

Medical Therapy

Trimethoprim-sulfamethoxazole is the drug of choice.

References

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Historical Perspective

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Pathophysiology

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

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Pathophysiology

Life Cycle

  • At time of excretion, the immature oocyst contains usually one sporoblast (more rarely two) 1.
  • In further maturation after excretion, the sporoblast divides in two (the oocyst now contains two sporoblasts); the sporoblasts secrete a cyst wall, thus becoming sporocysts; and the sporocysts divide twice to produce four sporozoites each 2.
  • Infection occurs by ingestion of sporocysts-containing oocysts: the sporocysts excyst in the small intestine and release their sporozoites, which invade the epithelial cells and initiate schizogony 3.
  • Upon rupture of the schizonts, the merozoites are released, invade new epithelial cells, and continue the cycle of asexual multiplication 4. Trophozoites develop into schizonts which contain multiple merozoites.
  • After a minimum of one week, the sexual stage begins with the development of male and female gametocytes 5.
  • Fertilization results in the development of oocysts that are excreted in the stool 1. Isospora belli infects both humans and animals.
Life cycle of Isospora belli


References

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Causes

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

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Overview

The coccidian parasite, Isospora belli, infects the epithelial cells of the small intestine, and is the least common of the three intestinal coccidia that infect humans.

References

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Differentiating Isosporiasis from other Diseases

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References

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Epidemiology and Demographics

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

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Overview

Isosporiasis occurs worldwide, especially in tropical and subtropical areas. Infection occurs in immunodepressed individuals, and outbreaks have been reported in institutionalized groups in the United States.

References

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Risk Factors

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Natural History, Complications and Prognosis

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Diagnosis

Diagnosis

History and Symptoms | Physical Examination | Laboratory Findings | Other Diagnostic Studies

Treatment

Treatment

Medical Therapy | Primary Prevention | Secondary Prevention | Cost-Effectiveness of Therapy | Future or Investigational Therapies

Case Studies

Case Studies

Case #1

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