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Cryptosporidiosis is an illness caused by the protozoan Cryptosporidium, a single-celled parasite. The most common symptom is diarrhea that is usually watery and profuse, and often accompanied by abdominal cramping. Nausea, vomiting, fever, headache, and loss of appetite may also occur. Rarely, the parasite can cause an inflammation of the gallbladder or infect the lining of the respiratory tract, causing pneumonia. Some persons infected with Cryptosporidium may not become ill.

Cryptosporidiosis 101

Crypto lives in the gut of infected humans or animals. An infected person or animal sheds Crypto parasites in their poop. An infected person can shed 10,000,000 to 100,000,000 Crypto germs in a single bowel movement. Shedding of Crypto in poop begins when symptoms like diarrhea begin and can last for weeks after symptoms stop. Swallowing as few as 10 Crypto germs can cause infection.

Crypto can be spread by:

  • Swallowing recreational water (for example, the water in swimming pools, fountains, lakes, rivers) contaminated with Crypto
    • Crypto’s high tolerance to chlorine enables the parasite to survive for long periods of time in chlorinated drinking and swimming pool water
  • Drinking untreated water from a lake or river that is contaminated with Crypto
  • Swallowing water, ice, or beverages contaminated with poop from infected humans or animals
  • Eating undercooked food or drinking unpasteurized/raw apple cider or milk that gets contaminated with Crypto
  • Touching your mouth with contaminated hands
    • Hands can become contaminated through a variety of activities, such as touching surfaces or objects (e.g., toys, bathroom fixtures, changing tables, diaper pails) that have been contaminated by poop from an infected person, changing diapers, caring for an infected person, and touching an infected animal
  • Exposure to poop from an infected person through oral-anal sexual contact

Crypto is not spread through contact with blood.

Symptoms of Crypto generally begin two to 10 days (average seven days) after becoming infected with the parasite. Symptoms include:

  • Watery diarrhea
  • Stomach cramps or pain
  • Dehydration
  • Nausea
  • Vomiting
  • Fever
  • Weight loss

Symptoms usually last about one to two weeks (with a range of a few days to four or more weeks) in people with healthy immune systems.

The most common symptom of cryptosporidiosis is watery diarrhea. Some people with Crypto will have no symptoms at all.

How is cryptosporidiosis diagnosed?

Cryptosporidiosis is a diarrheal disease that is spread through contact with the stool of an infected person or animal. The disease is diagnosed by examining stool samples. People infected with Crypto can shed the parasite irregularly in their poop (for example, one day they shed parasite, the next day they don’t, the third day they do) so patients may need to give three samples collected on three different days to help make sure that a negative test result is accurate and really means they do not have Crypto. Healthcare providers should specifically request testing for Crypto. Routine ova and parasite testing does not normally include Crypto testing.

What is the treatment for cryptosporidiosis?

Most people with healthy immune systems will recover from cryptosporidiosis without treatment. The following actions may help relieve symptoms:

  • Drink plenty of fluids to remain well hydrated and avoid dehydration. Serious health problems can occur if the body does not maintain proper fluid levels. For some people, diarrhea can be severe resulting in hospitalization due to dehydration.
  • Maintain a well-balanced diet. Doing so may help speed recovery.
  • Avoid beverages that contain caffeine, such as tea, coffee, and many soft drinks.
  • Avoid alcohol, as it can lead to dehydration.

Over-the-counter anti-diarrheal medicine might help slow down diarrhea, but a healthcare provider should be consulted before such medicine is taken.

A drug called nitazoxanide has been FDA-approved for treatment of diarrhea caused by Cryptosporidium in people with healthy immune systems and is available by prescription. Consult with your healthcare provider for more information about potential advantages and disadvantages of taking nitazoxanide.

Individuals who have health concerns should talk to their healthcare provider.

For more information, visit Treatment.

Note: Infants, young children, and pregnant women may be more likely than others to suffer from dehydration. Losing a lot of fluids from diarrhea can be dangerous—and especially life-threatening in infants. These people should drink extra fluids when they are sick. Severe dehydration may require hospitalization for treatment with fluids given through your vein (intravenous or IV fluids). If you are pregnant or a parent and you suspect you or your child are severely dehydrated, contact a healthcare provider about fluid replacement options.

No cleaning method is guaranteed to be completely effective against Crypto. However, you can lower the chance of spreading Crypto by taking the following precautions:

  • Wash linens, clothing, dishwasher- or dryer-safe soft toys, etc. soiled with poop or vomit as soon as possible.
    • Flush excess vomit or poop on clothes or objects down the toilet.
    • Use laundry detergent, and wash in hot water: 113°F or hotter for at least 20 minutes or at 122°F or hotter for at least 5 minutes.
    • Machine dry on the highest heat setting.
  • For other household object and surfaces (for example, diaper-change areas):
    • Remove all visible poop.
    • Clean with soap and water.
    • Let dry completely for at least four hours.
      • If possible, expose to direct sunlight during the four hours.
  • Wash your hands with soap and water after cleaning objects or surfaces that could be contaminated with Crypto.

Note: The best way to prevent the spread of Cryptosporidium in the home is by practicing good hygiene. Wash your hands frequently with soap and water, especially after using the toilet, after changing diapers, and before eating or preparing food. Alcohol-based hand sanitizers are not effective against Crypto.

Provider Information

This is a Wisconsin disease surveillance category II disease:

Wisconsin and public health follow-up guidelines:

Questions about Cryptosporidiosis? Contact us!
Phone: 608-267-9003 | Fax: 608-261-4976

Wisconsin Local Health DepartmentsRegional officesTribal agencies

Last revised October 7, 2021