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Pronounced: KRIP-toe-spo-rid-ee-OH-sis

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Cryptosporidiosis is an infection of the intestine which results in severe diarrhea. It is caused by a parasite called Cryptosporidium parvum .

Cryptosporidium parasites live in the intestines of infected people and animals. They can also live outside the body for a long time because they have a protective outer shell. The parasites contaminate objects and surfaces that people touch, as well as soil where food is grown and recreational waters where people swim.

Cryptosporidiosis is caused by swallowing the parasite. When the parasite enters your intestine, it comes out of its shell, multiplies, and may cause an infection. Eventually, it is passed from your body through a bowel movement.

Most healthy adults recover from this infection in a few weeks. However, it can be life threatening for young children, the elderly, and very sick people.

The Intestines

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You can get cryptosporidiosis by swallowing something that has come into contact with the feces of an infected person or animal.

Some sources of cryptosporidiosis are:

  • Humans and animals:
    • Contact with diapers or clothing that are contaminated with the infection
    • Contact with animal feces by touching animals, cleaning cages, or visiting barns
    • Sexual activity that involves contact with feces
  • Food:
    • Eating food grown in, or contaminated by, infected soil
    • Drinking unpasteurized milk, dairy products, or apple juice
    • Eating food that was handled by someone who is infected or washed in contaminated water
  • Water:
    • Accidentally swallowing water in contaminated recreational water, such as a lake, ocean, bay, stream, hot tub, swimming pool, or water park
    • Drinking water or ice that is contaminated

Risk Factors

A risk factor is something that increases your chance of getting a disease or condition. People who are at increased risk for cryptosporidiosis include:

  • Young children, especially if they are in day care
  • Day care workers or those who work in a group setting
  • People whose immune system is weakened by cancer, AIDS , or an organ transplant
  • People who engage in oral-anal sex
  • International travelers, backpackers, hikers, and campers


Symptoms of cryptosporidiosis usually begin about a week after infection. Some people will not have any symptoms at all.

Symptoms consist mainly of:

  • Watery diarrhea
  • Stomach cramps
  • Upset stomach, vomiting
  • Slight fever
  • Weakness
  • Weight loss
  • Dehydration

The symptoms may come and go before you are finally better.


To diagnose cryptosporidiosis, your doctor will take one or more stool samples to be examined in the laboratory.


People with healthy immune systems usually recover from cryptosporidiosis without needing treatment. Recovery can take several weeks and up to one month. If you have severe diarrhea, you may be given intravenous fluids or antidiarrheal drugs. A new drug call nitazoxanide has recently been approved to treat the diarrhea associated with cryptosporidiosis in healthy people.

People with a weakened immune system, particularly people with AIDS, have a greater risk of getting this infection. They are also likely to have a more severe and longer-lasting infection. Although treatment with antiretroviral drugs may help, these patients may be permanently infected.


There are several important measures you can take to lower your risk of getting cryptosporidiosis:

  • Wash your hands:
    • After using the toilet
    • After changing a diaper
    • Before handling or eating food
    • After contact with animals or soil
    • After contact with infected people
  • Drink safe water:
    • Boil water if you are unsure if it’s safe.
    • Avoid accidentally swallowing water when swimming in recreational water.
  • Eat safe food:
    • Wash vegetables that will be eaten raw
    • Drink only pasteurized milk and juice
  • Use precautions during sexual activity



AIDS Treatment Data Network

Centers for Disease Control and Prevention (CDC)

Centers for Disease Control and Prevention National Prevention Information Network

National Center for Infectious Diseases

National Institute of Allergy and Infectious Diseases
National Institutes of Health


Canadian HIV/AIDS Information Centre

Health Canada


Beers MH, Fletcher AJ, Jones TV, et al. The Merck Manual of Medical Information: Second Home Edition . Merck Research Laboratories: Whitehouse Station, NJ; 2003.

Cryptosporidiosis. Directors of Health Promotion and Education website. Available at Accessed September 19, 2005.

Cryptosporidiosis: a simple fact sheet. AIDS Treatment Data Network website. Available at Accessed September 19, 2005.

Cryptosporidium infection. Department of Health and Human Services. Centers for Disease Control and Prevention website. Available at Accessed September 19, 2005.

Last reviewed January 2008 by David L. Horn, MD, FACP

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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