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 objects.
• 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 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 or by having contact with soil, a person, or an item that has been contaminated with the parasite. 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.

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 and Diagnosis

Symptoms may begin abruptly 7 to 10 days after infection and consist mainly of abdominal cramps and profuse, watery diarrhea. Nausea, vomiting, loss of appetite, fever, and weakness may also occur. In people with a weakened immune system, symptoms 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).

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 several stool samples may be needed to find the parasite.

Did You Know... People with a healthy immune system typically do not need treatment for cryptosporidiosis.

Prevention and Treatment

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. 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), to eat only cooked foods, and to 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.

People with a healthy immune system typically recover on their own. Nitazoxanide is given to children to speed recovery and may be useful for healthy adults. However, it is usually ineffective in people who have AIDS and thus have a weakened immune system. If possible, the problem with the immune system should be treated. If people take drugs that suppress the immune system (immunosuppressants), the drugs should be stopped, or their doses decreased if possible. Unless the immune system problem is corrected, diarrhea may continue throughout life. In people with AIDS, antiretroviral drugs can improve immune function and relieve diarrhea caused by Cryptosporidium parvum, but such people may remain permanently infected. 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.

Last full review/revision March 2007 by Richard D. Pearson, MD