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Key Features

Essentials of Diagnosis

  • Acute diarrhea, especially in children in developing countries

  • Outbreaks of diarrhea secondary to contaminated water or food

  • Prolonged diarrhea in immunocompromised persons

  • Diagnosis mostly by identifying organisms in specially stained stool specimens

General Considerations

  • Causes of coccidiosis

    • Cryptosporidium spp, particularly C parvum and C hominis

    • Isospora belli

    • Cyclospora cayetanensis

    • Sarcocystis species

  • Sarcocystis infects many species

  • Humans are intermediate hosts (infected by ingestion of fecal sporocysts) for some species

  • Humans are definitive hosts for Sarcocystis bovihominis and Sarcocystis suihominis (infected by ingestion of tissue cysts in undercooked beef and pork, respectively)


  • Occurs worldwide, particularly in tropics and in regions where hygiene is poor

  • Clustering of cases occurs in households, day care centers, and among sexual partners

Clinical Findings

Symptoms and Signs

  • Usually asymptomatic

  • Gastrointestinal symptoms (eg, diarrhea)

  • Cysts in muscle may cause

    • Myalgias

    • Fever

    • Bronchospasm

    • Pruritic rash

    • Lymphadenopathy

    • Subcutaneous nodules

Differential Diagnosis

  • Infections caused by I belli, C cayetanensis, and Cryptosporidium species

  • Giardiasis

  • Viral gastroenteritis, eg, rotavirus

  • Other traveler's diarrhea, eg, Escherichia coli

  • Cryptosporidiosis

  • Other causes of diarrhea in AIDS, eg, cytomegalovirus colitis

  • Trichinosis


  • Eosinophilia

  • Elevated creatine kinase

  • Diagnosis is by identification of acid-fast organisms in stool or by identification of trophozoites or bradyzoites in tissue biopsies


  • No specific treatment is established

  • Patients may respond to albendazole or trimethoprim-sulfamethoxazole



  • Water purification

  • Immunocompromised patients should boil or filter drinking water and should consider avoidance of lakes and swimming pools

  • Routine precautions (handwashing, gloves, disinfection) should prevent institutional patient-to-patient spread


Didier  ES,  et al. Microsporidiosis: not just in AIDS patients. Curr Opin Infect Dis. 2011 Oct;24(5):490–5.
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Fayer  R,  et al. Human infections with Sarcocystis species. Clin Microbiol Rev. 2015 Apr;28(2):295–311.
[PubMed: 25715644]  
Marcos  LA,  et al. Intestinal protozoan infections in the immunocompromised host. Curr Opin Infect Dis. 2013 Aug;26(4):295–301.
[PubMed: 23806893]  
Shirley  DA,  et al. Burden of disease from cryptosporidiosis. Curr Opin Infect Dis. 2012 Oct;25(5):555–63.
[PubMed: 22907279]  

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