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Contributors: Neil Mendoza MD, Nana Aburjania MD, Paritosh Prasad MD
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Cryptosporidiosis is an intestinal infection caused by ingestion of the infective oocysts of Cryptosporidium species.

Transmission is primary by the fecal-oral route. Cryptosporidiosis is more common in conditions of crowding and poor sanitation, and infection is a major cause of diarrhea in children in developing countries. In developing countries, many adults may asymptomatically excrete oocysts, and oocysts can frequently be found on vegetables and can contaminate the water supply. In the United States, outbreaks have been associated with contaminated drinking water, contaminated recreational water (including lakes and public pools), and contaminated food.

The incubation period is usually 7-10 days (range 1-30 days).

Clinically, symptoms for cryptosporidiosis can vary widely. In immunocompetent hosts, diarrhea is usually self-limited (lasting 1-2 weeks). The diarrhea may be mild, or it may be voluminous and watery.

In immunocompromised hosts, including patients with AIDS, infection can cause devastating illness. The diarrhea can be severe and prolonged (lasting months), leading to dehydration. In this case, the illness could be life threatening, and some patients may require parenteral nutrition.

Elderly patients typically have more severe disease.

In addition to watery diarrhea, patients may also complain of nausea, vomiting, fever, and abdominal cramping. In immunocompromised patients, infection can also involve the biliary or respiratory tract.


A07.2 – Cryptosporidiosis

240370009 – Cryptosporidiosis

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Differential Diagnosis & Pitfalls

Other causes of infectious diarrhea:
Noninfectious diarrhea:
In immunocompromised patients:
  • Microsporidia – Stain for microsporidia should be obtained.
  • Mycobacterial species including the Mycobacterium avium complex – Acid fast stain and culture for mycobacteria should be obtained.
  • Cytomegalovirus and other viruses – Can cause colitis, diagnosis is usually made by biopsy.

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Last Updated:11/01/2022
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Patient Information for Cryptosporidiosis
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Contributors: Medical staff writer


Cryptosporidiosis is a parasitic infection in the intestines caused by the species Cryptosporidium. It is found worldwide and throughout the United States. It is a common cause of diarrhea in children – especially in developing countries  due to a lack of water treatment and food sanitation. Infection also occurs in developed countries, where Cryptosporidium may be spread in contaminated drinking water, public pools, lakes, and food.

Who’s At Risk

Risk factors include:
  • Living in nursing homes, dormitories, or crowded areas
  • Unsanitary living conditions
  • Exposure to contaminated water
  • Men who have sex with men
  • Handling animals as an occupation
  • Working or living with children in diapers

Signs & Symptoms

Cryptosporidiosis has the following symptoms, usually 1 week after infection:
  • Watery diarrhea
  • Dehydration
  • Weight loss
  • Fever
  • Nausea
  • Stomach cramps
  • Vomiting

Self-Care Guidelines

Drink fluids with electrolytes such as Gatorade to replace lost fluid from diarrhea and vomiting.

  • Wash hands before preparing or eating food
  • Wash hands after using toilet, changing diapers, etc.
  • Don't swim in a pool if you have diarrhea
  • Don't swallow pool water

When to Seek Medical Care

Seek medical care if you develop persistent watery diarrhea that does not improve within a few days.


Your health care provider may prescribe anti-parasitic drugs to attack the Cryptosporidium organisms, and, in some cases, anti-motility agents to relieve diarrhea symptoms.
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A medical illustration showing key findings of Cryptosporidiosis (Mild) : Diarrhea, Fever, Nausea, Malaise, Anorexia, Cramping abdominal pain
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