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Cryptosporidium enteritis

Cryptosporidiosis

Cryptosporidium enteritis is an infection of the small intestine that causes diarrhea. The parasite cryptosporidium causes this infection.

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Causes

Cryptosporidium has recently been recognized as a cause of diarrhea worldwide in all age groups. It has a greater effect on people with a weakened immune system, including:

• People who take medicines to suppress their immune system
• People with HIV/AIDS
• Transplant recipients

In these groups, this infection is not just bothersome, but can lead to severe and life-threatening loss of muscle and body mass (wasting) and malnutrition.

The major risk factor is drinking water contaminated with stool (feces). People at higher risk include:

• Animal handlers
• People who are in close contact with infected people
• Young children

Outbreaks have been linked to:

• Drinking from contaminated public water supplies
• Drinking unpasteurized cider
• Swimming in contaminated pools and lakes

Some outbreaks have been very large.

Symptoms

Symptoms of infection include:

• Abdominal cramping
• Diarrhea, which is often watery, non-bloody, large-volume, and occurs many times a day
• General sick feeling (malaise)
• Malnutrition and weight loss (in severe and prolonged cases)
• Nausea

Exams and Tests

These tests may be done:

• Antibody test to see if cryptosporidium is in the stool
• Stool polymerase chain reaction (PCR) test to detect multiple pathogens, including cryptosporidium
  
• Intestinal biopsy (rare)
• Stool exam with special techniques (AFB staining)
• Stool exam using a microscope to look for the parasites and their eggs

Treatment

There are several treatments for cryptosporidium enteritis.

The best approach is to improve immune function in people who have a weakened immune system. In people with HIV/AIDS, this can be done by using HIV-antiviral medicines. Using this type of treatment can lead to a complete remission of cryptosporidium enteritis.

Medicines such as nitazoxanide have been used in children and adults. Other medicines that are sometimes used include:

• Nitazoxanide
• Paromomycin

These medicines often help only for a little while. It is common for the infection to return.

Outlook (Prognosis)

In healthy people, the infection will clear up, but it can last up to a month. In people with a weakened immune system, long-term diarrhea may cause weight loss and malnutrition.

Possible Complications

These complications can occur:

• Inflammation of a bile duct
• Inflammation of the gallbladder
• Inflammation of the liver (hepatitis)
• Malabsorption (not enough nutrients being absorbed from the intestinal tract)
• Inflammation of the pancreas (pancreatitis)
• Loss of body mass that causes extreme thinness and weakness (wasting syndrome)

When to Contact a Medical Professional

Contact your health care provider if you develop watery diarrhea that does not go away within a few days, especially if you have a weakened immune system.

Prevention

Proper sanitation and hygiene, including handwashing, are important measures for preventing this illness.

Certain water filters can also reduce risk by filtering out the cryptosporidium eggs. However, the pores of the filter must be smaller than 1 micron to be effective. If you have a weakened immune system, ask your provider if you need to boil your water.

Related Information

References

Caravedo MA, Tanabe MB, White AC. Cryptosporidiosis (Cryptosporidium species). In: Blaser MJ, Cohen JI, Holland SM, et al, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 10th ed. Philadelphia, PA: Elsevier; 2026:chap 288.

Centers for Disease Control and Prevention website. About Crypto infections. www.cdc.gov/cryptosporidium/about/index.html. Updated May 27, 2025. Accessed April 15, 2026.

Fleckenstein JM. Approach to the patient with suspected enteric infection. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 262.

Warren CA, Lima AAM. Cryptosporidiosis. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 321.

Review Date: 3/1/2026  

Reviewed By: Jatin M. Vyas, MD, PhD, Roy and Diana Vagelos Professor in Medicine, Columbia University Vagelos College of Physicians and Surgeons, Division of Infectious Diseases, Department of Medicine, New York, NY. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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