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Cryptosporidiosis ˌkrip-tō-spȯr-ˌid-ē-ˈō-səs

By Richard D. Pearson, MD, Emeritus Professor of Medicine, University of Virginia School of Medicine

Cryptosporidiosis is an intestinal infection caused by Cryptosporidium, a protozoan. The main symptoms are abdominal cramping and diarrhea.

  • People acquire the infection by consuming contaminated water or food or by having contact with contaminated people or animals.

  • Abdominal cramping and watery diarrhea may begin suddenly, sometimes accompanied by nausea, vomiting, fever, and weakness.

  • Doctors diagnose the infection by examining or analyzing a stool sample for signs of the parasite.

  • Adequate sanitation and hand washing can help prevent spread of the infection, as can boiling water before drinking it.

  • Healthy people often recover on their own, but people with a weakened immune system require treatment with drugs.

Cryptosporidium parasites are protozoans that infect people and many kinds of animals throughout the world. The infection is acquired by

  • Ingesting parasites in water or food contaminated by human or animal feces

  • Having contact with soil, a person, or an item that has been contaminated with the parasite

For example, people may acquire the infection when they accidentally swallow contaminated water from swimming pools, water parks, hot tubs, or lakes. Cryptosporidiosis is a common cause of diarrhea among children living in developing areas where sanitation is poor. It occasionally occurs among travelers to such areas. People with a weakened immune system, particularly those with AIDS, are prone to cryptosporidiosis and are more likely to have severe, persistent disease.

Did You Know...

  • People with a healthy immune system typically do not need treatment for cryptosporidiosis.

The eggs (oocysts) of Cryptosporidium are very hardy and are frequently present in surface water in the United States. The parasite is not killed by freezing or by the usual levels of chlorine in swimming pools or drinking water.

Symptoms of Cryptosporidiosis

Cryptosporidiosis symptoms may begin abruptly about 7 days after people are infected and consist mainly of abdominal cramps and profuse, watery diarrhea. Nausea, vomiting, loss of appetite, fever, and weakness may also occur. Symptoms usually last 1 to 2 weeks, then subside.

In people with a weakened immune system, symptoms of cryptosporidiosis may begin gradually, and the diarrhea can vary from mild to severe (as much as 3 to 4 gallons of watery stool per day in people with AIDS) and may persist for a long time.

Diagnosis of Cryptosporidiosis

  • Stool tests

To diagnose cryptosporidiosis, a doctor sends a stool sample to be tested for a protein released by the parasite (antigen testing). Another approach is to examine stool under a microscope, but this method is less sensitive, and several stool samples may be needed to find the parasite.

Prevention of Cryptosporidiosis

Cryptosporidiosis prevention involves adequate sanitation and hand washing, particularly in health care facilities and day care centers and after contact with soil, animals, or infected people. People should not drink or swallow water that could be contaminated, such as that from a swimming pool, stream, or lake or in an area where sanitation is poor.

When public health departments discover a localized outbreak of the disease, they typically advise people to

  • Boil drinking water (including water for toothbrushing and food washing)

  • Eat only cooked foods

  • Avoid unpasteurized milk and juice

Tap water filters that use reverse osmosis or have the words "absolute 1 micron" or "tested and certified by NSF Standard 53 for cyst removal/reduction" are effective. Other types of filters may not be.

Treatment of Cryptosporidiosis

  • For people with persistent diarrhea, nitazoxanide

  • For people with AIDS, treatment of the HIV infection and nitazoxanide

  • If diarrhea is severe, fluids and an antidiarrheal drug

People with a healthy immune system typically recover on their own. If such people have persistent diarrhea, nitazoxanide (an antiparasitic drug) may help speed recovery.

For people who have AIDS, the most important therapy is to treat the HIV infection. When such treatment strengthens the weakened immune system, diarrhea is usually reduced. Doctors also give them high doses of nitazoxanide. However, unless the immune system problem is corrected, diarrhea may continue throughout life.

People with severe diarrhea may require treatment with fluids, given by mouth or by vein, and antidiarrheal drugs such as loperamide. However, loperamide may not help people with AIDS.

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