Cryptosporidium infection

Cryptosporidium was first pinpointed as a cause of gastrointestinal disease in 1976, and was found in the 1980s to be a common cause of diarrhea in people infected with HIV. Cryptosporidium infection (cryptosporidiosis) is a gastrointestinal disease whose primary symptom is diarrhea. The illness begins when a tiny one-celled parasite enters your body and travels to your small intestine. Cryptosporidium, which means “hidden spore,” then begins its life cycle inside your body — burrowing into the walls of your intestines and then later being shed in your feces.  In most healthy people, cryptosporidium infection produces a bout of watery diarrhea and resolves within a week or two. For people with a compromised immune system, it can become life-threatening without proper treatment.


The primary symptom of cryptosporidiosis is watery diarrhea that lasts up to two weeks. First signs usually appear one to two weeks after infection with cryptosporidium.

Other signs and symptoms of cryptosporidium infection include:

  • Dehydration
  • Malnutrition
  • Weight loss
  • Stomach cramps or pain
  • Fever
  • Nausea
  • Malaise
  • Vomiting

Some people with cryptosporidium infection, especially people with a healthy immune system, may have no symptoms.


Cryptosporidium infection begins when you ingest the cells of one of nearly a dozen species of the cryptosporidium parasite. The Cryptosporidium parvum (C. parvum) species is responsible for the majority of infections in humans.

The germs then travel to your intestinal tract, where they settle into the walls of your intestines. Eventually, more cells are produced and shed in massive quantities into your feces, where they remain highly contagious.

You can become infected with cryptosporidium by touching anything that has come in contact with contaminated feces. Methods of infection include:

Swallowing or putting something contaminated with cryptosporidium into your mouth
Drinking water contaminated with cryptosporidium
Swimming in water contaminated with cryptosporidium and accidentally swallowing some of it
Eating uncooked food contaminated with cryptosporidium
Touching your hand to your mouth if your hand has been in contact with a contaminated surface or object
Having close contact with other infected people or animals — especially their feces — whereby the parasite is transmitted from your hands to your mouth

Cryptosporidium and giardia — another one-celled parasite — are among the most common causes of diarrhea in humans. These parasites are difficult to eradicate because they are resistant to many disinfectants and aren’t effectively removed by many filters. They can also survive in the environment for many months at varying temperatures.


The simplest way to diagnose cryptosporidium infection is a method called an acid-staining test, which identifies cryptosporidium under a microscope. To obtain cells for the analysis, your doctor might ask for a stool sample, or in more extreme cases, take a tissue sample (biopsy) from your colon for the test.

Your doctor might also order a standard stool culture. Although this test cannot detect the presence of cryptosporidium, it may help rule out other bacterial pathogens.

Once it’s clear that your infection is cryptosporidium, you may need further testing to check for development of serious complications. For example, checking liver and gallbladder function may determine whether the infection has spread.

If you have both AIDS and cryptosporidiosis, a T cell count — which measures the level of a certain white blood cell that’s part of your immune system — can help predict the duration of the cryptosporidiosis. A higher T cell count means you’re more likely to recover quickly, while a lower count means you may need to be monitored for further complications.


Cryptosporidium infection itself isn’t life-threatening. However, if you’ve had a transplant or if you have a weakened immune system, developing complications can be dangerous.

For example, more than half the people with both cryptosporidiosis and HIV develop chronic disease or associated infections. The infection is also more likely to travel to your biliary system — a group of organs and ducts including your gallbladder and pancreas — if you have a compromised immune system.

Complications of cryptosporidium infection include:

  • Malnutrition
  • Severe dehydration
  • Weight loss of more than 10 percent of original body weight (wasting syndrome)
  • Inadequate absorption of nutrients from your intestinal tract (malabsorption)
  • Infection of your biliary system
  • Inflammation of a bile duct (cholangitis)
  • Inflammation of your gallbladder (cholecystitis)
  • Inflammation of your liver (hepatitis)
  • Inflammation of your pancreas (pancreatitis)
  • Lactose intolerance


There’s no reliable treatment for cryptosporidiosis, and recovery usually depends on the health of your immune system. Most healthy people recover within 10 days to two weeks without medical attention.

If you have a compromised immune system, the illness can endure and lead to significant malnutrition and wasting. The goal of treatment is to alleviate symptoms and improve your immune response. Cryptosporidium treatment options include:

Anti-parasitic drugs. These medications can help alleviate diarrhea by attacking the metabolic processes of the cryptosporidium organisms. These drugs include nitazoxanide (Alinia), paromomycin (Humatin) and azithromycin (Zithromax).
Anti-motility agents. These medications slow down the movements of your intestines and increase fluid absorption to relieve diarrhea and restore normal stools. These medications include loperamide and its derivatives (Anti-Diarrheal Formula, Imodium).

Fluid replacement. You’ll need replacement of fluids and electrolytes — minerals such as sodium, potassium and calcium that maintain the balance of fluids in your body — lost to persistent diarrhea, either orally or intravenously. These precautions will help keep your body hydrated and functioning properly.
Anti-retroviral therapies . If you have HIV/AIDS, highly active anti-retroviral therapy (HAART) can reduce the viral load in your body and boost your immune response. Restoring your immune system to a certain level may completely resolve symptoms of cryptosporidiosis.


Cryptosporidium infection is contagious, so take precautions to avoid spreading the parasite to others.

All preventive methods aim to reduce or prevent the transmission of the cryptosporidium germs that are shed in human and animal feces. Precautions are especially important for people with compromised immune systems. Follow these suggestions:

Practice good hygiene. Wash your hands with soap and water after using the toilet, changing diapers and before and after eating.
Thoroughly wash all fruits and vegetables that you will eat raw.
Purify drinking water if you have a weakened immune system or are traveling in an area with a high risk of infection. Methods include filtering and boiling (at least one minute at a rolling boil).
Limit swimming activities in lakes, streams and public swimming pools, especially if the water is likely to be contaminated or if you have a compromised immune system.
Avoid fecal exposure during sexual activity.
Handle newborn farm and domestic animals with care. Be sure to wash your hands after handling the animals.