How Do You Treat Water for Cryptosporidium?

Patient Presentation
A 16-year-old male came to clinic with several days of diarrhea that he describes as loose and watery and occurred with some urgency. He denied blood in the stool, fevers, chills, nausea, emesis, abdominal cramping or rashes. He denied any significant weight loss and was urinating well. He had been camping with several other teenage boys just before the diarrhea occurred. They had camped on farmland that was used for dairy animals and crops. “We drank the water from the creek but we did boil it,” he said. He said at least one other camper also had diarrhea. The past medical history showed a healthy male with several athletically-related orthopaedics injuries.

The pertinent physical exam showed a well-developed male. His weight was the same as at a recent well-child examination. His abdominal examination was negative. The diagnosis of a diarrheal illness caused by viral, bacterial or protozoan organisms was made. As he was otherwise well and was well-hydrated, no specific treatment was done but continued hydration and good hygiene was advised. The laboratory evaluation of stool cultures for bacteria and parasites were sent because of the illness duration. The state epidemiology laboratory did extended testing because of the history and diagnosed Cryptosporidium. The state epidemiology team followed up with the patient and the contacts but all had improved when contacted.

Cryptosporidium is an oocyte-forming coccidian protozoan. It is transmitted through ingestion of contaminated food, water, or contact with infected persons or animals (particularly preweaned calves). It is a common cause of diarrhea from contaminated recreational water supplies including lakes, ponds, streams, and pool and waterpark water. It has been associated with occupational exposures in agricultural settings and veterinary schools. Emergencies where calves or biological samples are involved have caused transmission of Cryptosporium to first responders. Others at risk include young children and those who care for them (i.e. parents, child care professionals), swimmers who swallow contaminated water, those exposed to human feces through sexual contact, and domestic and international travelers. Travelers who drink unfiltered, untreated water are at higher risk. People who are immunocompromised are also at higher risk.

The most common symptom is watery diarrhea that begins about 7-10 days (range 2-26 days) after infection and is self-limited. Excretion can be intermittent and last for weeks. Other symptoms are abdominal cramps, decreased appetite and weight loss, emesis, fever, fatigue, headache and joint pain. Cryptosporidium testing is usually not included in routine ova and parasite testing so specific testing often needs to be requested. Multiple stool samples may be needed because of the intermittent excretion.

Immunocompetent patients are usually not treated, but nitazoxanide can be used for both immunocompetent and immunocompromised patients.

Common causes of diarrhea can be found here.

Learning Point
Recreational water supplies are a common source as the pool chemicals (often halogens such as chlorine and bromine) are ineffective against Cryptosporidium. Even well maintained facilities can have tainted water and small amounts can cause disease. Cryptosporium can lives for days outside the host. It is a very hearty organism and difficult to kill.

Bathers should not use recreational water if they have open cuts, or sores to help prevent transmission. Swallowing water is never recommended. Inadequately treated water should be avoided. This includes ice or water from lakes, streams, ponds, rivers, springs or shallow wells where the water may be unsafe. Water supplies can be appropriately treated for Cryptosporidum by:

  • Using bottled water instead including for personal hygiene and food preparation.
  • Heating the water to a rolling boil and boiling for 1 minute.
  • Using a water filter. This should be with an absolute pore size of 1 micrometer or smaller or use of an NSF Standard 53 or NSF Standard 58 filter for cyst and oocyst reduction. If a filter is used, then the water will still need additional treatment to kill or inactivate viruses and bacteria.
  • Using chlorine dioxide (not the pool chemical) appropriately
  • Using ultraviolet light appropriately

Detailed information regarding water disinfection for travelers can be found here.

Questions for Further Discussion
1. List other infectious diseases transmitted primarily through water.
2. What are the common causes of traveler’s diarrhea and how is it treated?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for this topic: Cryptosporidiosis.

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

Centers for Disease Control. Parasites – Cryptosporidium. Available from the Internet at (rev. 3/9/11, cited 1/6/15).

American Academy of Pediatrics. Cryptosporidiosis, In Pickering LD, Baker CJ, Kimberlin DW, Long SS, eds. Red Book: 2012 Report of the Committee on Infectious Diseases. 29th edit. Elk Grove Village, IL: American Academy of Pediatrics; 2012;296-98.

Centers for Disease Control. Traveler’s Health Cryptosporidiosis. (rev. 8/1/13, cited 1/6/15)

Webb LM, Tubach SA, Hunt DC. Outbreak of cryptosporidiosis among responders to a rollover of a truck carrying calves – Kansas, April 2013. MMWR Morb Mortal Wkly Rep. 2014 Dec 19;63(50):1185-8.


Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa Children’s Hospital