eMedicine Specialties > Infectious Diseases > Parasitic Infections

Isosporiasis: Differential Diagnoses & Workup

Author: Venkat R Minnaganti, MD, Consulting Staff, Department of Medicine, Winthrop University Hospital; Clinical Instructor, Department of Internal Medicine, Division of Infectious Disease, State University of New York School of Medicine at Stony Brook
Contributor Information and Disclosures

Updated: Oct 24, 2008

Differential Diagnoses

Amebiasis
Intestinal Radiation Injury
Bacterial Overgrowth Syndrome
Irritable Bowel Syndrome
Crohn Disease
Microsporidiosis
Cryptosporidiosis
Norwalk Virus
Cyclospora
Sarcosporidiosis
Diverticulitis
Strongyloidiasis
Eosinophilic Gastroenteritis
Ulcerative Colitis
Food Poisoning
Yersinia Enterocolitica Infection
Gastroenteritis, Bacterial
Giardiasis
Inflammatory Bowel Disease

Workup

Laboratory Studies

  • The diagnosis of isosporiasis is based on a combination of clinical, epidemiological, and diagnostic tests.
  • Routine laboratory tests are not diagnostic, but peripheral eosinophilia is an important clue.
  • Stool specimen features include the following:
    • Large oocysts of I belli are observed on modified acid-fast stains of stool specimens (see Image 1).
    • Multiple specimens or specimen concentration increases diagnostic yield.
    • Charcot-Leyden crystals are observed in stool specimens.
    • Polymorphonuclear leukocytes (PMNs) are not observed in fecal specimens.
  • Serologic tests for isosporiasis are not available.

Imaging Studies

  • Nonspecific radiographic findings (eg, prominent mucosal folds, thickening of intestinal wall) may be observed.
  • If performed as a part of workup for malabsorption, I belli may be observed with electron microscopy of tissue specimens.

Other Tests

  • Auramine-rhodamine fluorescent stain
  • Modified Kinyoun acid-fast stain
  • Ultraviolet autofluorescence microscopy - A simple rapid test to identify I belli
  • Zinc sulfate or sugar flotation - The most sensitive stool concentration technique
  • Real-time polymerase chain reaction (PCR) test (promising in recent studies)4

Procedures

  • Examination of duodenal aspirate or string test may aid in the diagnosis of isosporiasis.
  • A small-bowel biopsy is not a routine test for diagnosis of isosporiasis.

Histologic Findings

Nonspecific findings of isosporiasis observed in small-bowel biopsy specimens include mucosal atrophy, shortened villi, hypertrophic crypts, and lamina propria infiltrated with eosinophils. I belli may be observed in the cytoplasm of enterocytes with electron microscopy.

More on Isosporiasis

Overview: Isosporiasis
Differential Diagnoses & Workup: Isosporiasis
Treatment & Medication: Isosporiasis
Follow-up: Isosporiasis
Multimedia: Isosporiasis
References

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Further Reading

Keywords

isosporiasis, Isospora belli, I belli, Isospora belli infection, I belli infection, extraintestinal isosporiasis, disseminated isosporiasis, intestinal parasitic infections, Isospora belli enteritis, I belli enteritis, Cryptosporidium, Cyclospora, Toxoplasma

Contributor Information and Disclosures

Author

Venkat R Minnaganti, MD, Consulting Staff, Department of Medicine, Winthrop University Hospital; Clinical Instructor, Department of Internal Medicine, Division of Infectious Disease, State University of New York School of Medicine at Stony Brook
Venkat R Minnaganti, MD is a member of the following medical societies: All India Ophthalmological Society, American College of Physicians, American Medical Association, American Society for Microbiology, American Society for Microbiology, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

Medical Editor

Klaus-Dieter Lessnau, MD, FCCP, Clinical Associate Professor of Medicine, New York University School of Medicine; Medical Director, Pulmonary Physiology Laboratory; Director of Research in Pulmonary Medicine, Department of Medicine, Section of Pulmonary Medicine, Lenox Hill Hospital
Klaus-Dieter Lessnau, MD, FCCP is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, American Medical Association, American Society for Artificial Internal Organs, American Thoracic Society, Physicians for Social Responsibility, and Society of Critical Care Medicine
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

John W King, MD, Professor of Medicine, Section of Infectious Diseases, Louisiana State University Health Sciences Center; Director, Viral Therapeutics Clinics for Hepatitis; Consulting Staff, Department of Infectious Diseases, Overton Brook Veterans Affairs Medical Center
John W King, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians, American Federation for Medical Research, American Society for Microbiology, Association of Subspecialty Professors, Infectious Diseases Society of America, and Sigma Xi
Disclosure: emedicine $50.00 author of chapter

CME Editor

Eleftherios Mylonakis, MD, Clinical and Research Fellow, Department of Internal Medicine, Division of Infectious Diseases, Massachusetts General Hospital
Eleftherios Mylonakis, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians, American Society for Microbiology, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

Chief Editor

Michael Stuart Bronze, MD, Professor, Stewart G Wolf Chair in Internal Medicine, Department of Medicine, University of Oklahoma Health Science Center
Michael Stuart Bronze, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physician Executives, American College of Physicians, American College of Physicians-American Society of Internal Medicine, American Federation for Clinical Research, American Medical Association, American Society for Microbiology, Association of Professors of Medicine, Association of Program Directors in Internal Medicine, Infectious Diseases Society of America, Oklahoma State Medical Association, and Southern Society for Clinical Investigation
Disclosure: Nothing to disclose.

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