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Key Features

Essentials of Diagnosis


  • Mild to severe diarrhea

  • Abdominal cramps, nausea, fatigue, anorexia, fever


  • Infection can be severe and prolonged

  • Chronic fulminant diarrhea

  • Weight loss

General Considerations

  • Causes of coccidiosis

    • Cryptosporidium spp (eg, C parvum and C hominis)

    • Isospora belli

    • Cyclospora cayetanensis

    • Sarcocystis species

  • The infectious agents are oocysts (spores) transmitted by contaminated water or food

  • Cyclospora

    • Infects only humans

    • Requires time (about 7 days) outside the host to sporulate and become infectious

  • Outbreaks in the United States have been attributed to imported fresh produce

  • Infection causes

    • Endemic childhood gastroenteritis (especially in malnourished children in developing countries)

    • Traveler's diarrhea

    • Institutional and community outbreaks of diarrhea

    • Acute and chronic diarrhea in immunosuppressed patients, in particular those with AIDS


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

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

Clinical Findings

Symptoms and Signs

  • The incubation period is 1–11 days

  • Infections can be asymptomatic

  • Watery diarrhea

  • Abdominal cramps, nausea, fatigue, anorexia, fever (in 25% of cases)

  • Symptoms typically last for 2 weeks or longer and may persist for months

  • Relapses of diarrhea are common

  • Diarrhea may be preceded by a flu-like prodrome and followed by persistent fatigue

  • In immunocompromised patients, infection is typically more severe and prolonged, with chronic fulminant watery diarrhea and weight loss

Differential Diagnosis

  • C parvum, I belli, S bovihominis, and S suihominis

  • Giardiasis

  • Viral gastroenteritis, eg, rotavirus

  • Other traveler's diarrhea, eg, Escherichia coli

  • Cholera

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


Laboratory Tests

  • Diagnosis is made by examination of stool wet mounts or after modified acid-fast staining

  • Multiple specimens may need to be examined to make a diagnosis

  • The organism can also be identified in small bowel aspirates or biopsy specimens



  • Trimethoprim-sulfamethoxazole (TMP-SMZ)

    • 160/800 mg two to four times daily for 10 days

    • Higher doses may be needed for patients with AIDS

  • Pyrimethamine

    • An alternative therapy

    • Dosage is 75 mg orally in four divided doses with folinic acid (10–25 mg/day orally)

  • For patients with AIDS, long-term maintenance (160 mg/800 mg three times weekly) helps prevent relapse

  • For patients intolerant of TMP-SMZ, ciprofloxacin (500 mg orally twice daily for 7 days) showed efficacy, but with less ability to clear the organism than TMP-SMZ


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