Cryptosporidium infection (cryptosporidiosis) is an illness caused by tiny, one-celled cryptosporidium parasites. When cryptosporidia (krip-toe-spoe-RID-e-uh) enter your body, they travel to your small intestine and then burrow into the walls. Later, they're shed in your feces.

In most healthy people, a cryptosporidium infection produces a bout of watery diarrhea. The infection usually goes away within a week or two. If you have a compromised immune system, a cryptosporidium infection can become life-threatening without treatment.

You can help prevent a cryptosporidium infection by practicing good hygiene and avoiding swallowing water from pools, recreational water parks, lakes and streams.

The first signs and symptoms of cryptosporidium infection, which usually appear within a week after infection, might include:

• Watery diarrhea
• Dehydration
• Lack of appetite
• Weight loss
• Stomach cramps or pain
• Fever
• Nausea
• Vomiting

Symptoms can last for up to two weeks, though they might come and go for up to a month, even in people with healthy immune systems. Some people with cryptosporidium infection have no symptoms.

When to see a doctor

Seek medical attention if you develop watery diarrhea that does not get better within a few days.

Cryptosporidium infection begins when the one-celled cryptosporidium parasites get into your body through your mouth. Some strains of cryptosporidium can cause more serious disease.

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

You can become infected with cryptosporidia by touching anything that has come in contact with contaminated feces. You can get infected by:

• Drinking contaminated water that contains cryptosporidium parasites
• Swimming in contaminated water that contains cryptosporidium parasites and accidentally swallowing some of it
• Eating uncooked, contaminated food that contains cryptosporidia
• Touching your hand to your mouth if your hand has been in contact with a contaminated surface, object, person or animal

If you have a compromised immune system from HIV/AIDS, you're more susceptible to illness from cryptosporidium parasites than is a person with a healthy immune system. People with HIV/AIDS can develop severe symptoms and a chronic, persistent form of disease that can be difficult to treat.

Hardy parasites

Cryptosporidium parasites are one of the more common causes of infectious diarrhea in humans. This parasite is difficult to to get rid of because it's resistant to many disinfectants and many filters don't remove it.

Cryptosporidia can survive for months at varying temperatures, though the parasite can be destroyed by boiling.

People who are at increased risk of developing cryptosporidiosis include:

• Children, particularly those wearing diapers, who attend child care centers
• Parents of infected children
• Child care workers
• Animal handlers
• Those who engage in oral-to-anal sexual activity
• International travelers, especially those traveling to developing countries
• Backpackers, hikers and campers who drink untreated, unfiltered water
• Swimmers who swallow water in pools, lakes and rivers
• People who drink water from shallow, unprotected wells

Complications of cryptosporidium infection include:

• Malnutrition resulting from poor absorption of nutrients from your intestinal tract
• Severe dehydration
• Significant weight loss
• Inflammation of the passage between your liver, gallbladder and small intestine (bile duct)
• Inflammation of your gallbladder, liver or pancreas

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

Cryptosporidium infection is contagious, so take precautions to avoid spreading the parasite to other people. There's no vaccine to prevent a cryptosporidium infection.

To help prevent cryptosporidium infection:

• Practice good hygiene. Wash your hands for at least 20 seconds with soap and water after using the toilet and changing diapers, and before and after eating. Alcohol-based hand sanitizers don't kill the germs that cause cryptosporidium infection.
• Thoroughly wash with uncontaminated water all fruits and vegetables that you will eat raw, and avoid eating food you suspect could be contaminated. If you're traveling in a developing country, avoid uncooked foods.

• Purify drinking water if you have a weakened immune system or are traveling in an area with a high risk of infection. Methods include boiling — at least one minute at a rolling boil — or filtering, although filtering might not be as effective as boiling.

  Be sure to use a filter that meets the NSF International standard 53 or 58 requirements for cyst and oocyst reduction. You'll need a separate water filter for bacteria and viruses.

• Avoid fecal exposure during sexual activity.

Always avoid swimming when you have diarrhea. If you know you've had a cryptosporidium infection, don't go swimming for at least two weeks after your symptoms go away because you can still be contagious.

The following tests can diagnose cryptosporidium infection:

• Acid-staining test. To get cells for the analysis, your doctor might ask for a stool sample or, possibly, take a tissue sample (biopsy) from your intestine. The sample is then looked at under a microscope.
• Stool culture. A culture of a sample of your stool can't detect cryptosporidium, but it can help rule out other bacterial pathogens.
• Other tests. Once it's clear that your infection is caused by cryptosporidium parasites, you might need further testing to check for complications. For example, checking liver and gallbladder function might determine whether the infection has spread.

Most healthy people with cryptosporidiosis recover within two weeks without treatment.

If you have a compromised immune system, the treatment goal is to relieve symptoms and improve your immune response. Cryptosporidiosis treatment options include:

• Anti-parasitic drugs. Medications such as nitazoxanide (Alinia) can help relieve diarrhea by attacking the parasites. Azithromycin (Zithromax) may be given with one of these medications in people with compromised immune systems.
• Anti-motility agents. These medications slow the movements of your intestines and increase fluid absorption to relieve diarrhea and restore normal stools. Anti-motility drugs include loperamide and its derivatives (Imodium A-D, others). Talk with your doctor before using these medications.
• Fluid replacement. Persistent diarrhea can cause you to become dehydrated. You'll need either oral or intravenous replacement of fluids and electrolytes — minerals, such as sodium, potassium and calcium, that maintain the balance of fluids in your body.
• Antiretroviral therapies. If you have HIV/AIDS, highly active antiretroviral therapy can reduce the viral load in your body and boost your immune response. Restoring your immune system to a certain level might rid you of the symptoms of cryptosporidiosis.

You're likely to start by seeing your family doctor. In some cases, he or she may refer you to a doctor who specializes in infectious diseases or a doctor who specializes in disorders of the gastrointestinal tract (gastroenterologist).

Here's some information to help you get ready for your appointment.

What you can do

Make a list of:

• Your symptoms, including any that may seem unrelated to the reason for which you scheduled the appointment, and when the began
• Key personal information, including recent travel, especially to other countries or to large recreational swimming areas or water parks
• All medications, vitamins and and other supplements you take, including doses
• Questions to ask your doctor

For cryptosporidiosis, basic questions to ask your doctor include:

• What's the most likely cause of my symptoms?
• Are there other possible causes?
• What tests do I need?
• What treatments do you recommend?
• Are there dietary restrictions I need to follow?
• Are there brochures or other printed material I can have? What websites do you recommend?

Don't hesitate to ask other questions.

What to expect from your doctor

Your doctor is likely to ask you questions, such as:

• How severe are your symptoms?
• Does anything seem to improve your symptoms?
• Does anything make your symptoms worse?
• Have you been swimming recently?
• Have you traveled out of the country recently?

What you can do in the meantime

While you're waiting to see your doctor, drink plenty of fluids.