Symptoms tend to wax and wane but remit on their own in 2 to 4 weeks in immunologically healthy people. In other groups of immunodeficient persons, such as cancer chemotherapy patients, onset of illness can be explosive with cholera-like symptoms, but the disease tends to last only slightly longer than in otherwise healthy people. Supportive care via fluid and electrolyte replacement is essential. The oocysts are considered infective as soon as they are passed in stool and can remain infective outside the body for 2 to 6 months in a moist environment. The infectious dose for cryptosporidiosis infection is low.
Diagnosis is made by staining stools.
The fewer the organisms, the more difficult the diagnosis. Excretion can be intermittent, and so the parasite may not be detected in every stool. Most excretion occurs within the first 72 hours of infection. A simple, modified Kinyoun stain can be used and is commonly employed. Recently, EIA and FA tests have become available to detect Cryptosporidia in stools.