Cryptosporidium enteritis

Cryptosporidium enteritis is an infection of the intestines caused by a microscopic parasite called Cryptosporidium. It is often shortened to “Crypto.” Enteritis means inflammation of the small intestine.

The main symptom is frequent watery diarrhea. The infection can also cause stomach cramps, nausea, loss of appetite, and tiredness. Symptoms often settle without specific medicine in people with a healthy immune system, but fluid loss can lead to dehydration.

Crypto spreads through tiny amounts of infected stool. You can become infected by swallowing contaminated water or food, touching contaminated surfaces, or having close contact with an infected person or animal.

The parasite has a protective outer shell. This allows it to survive outside the body and makes it more resistant to chlorine than many other germs. Crypto can therefore spread in swimming pools and other recreational water, even when the water is treated.

People with severely weakened immune systems can develop longer-lasting or more serious symptoms. Restoring immune function may then be an important part of treatment.

Symptoms usually begin within several days of exposure, although the timing is not the same for everyone. Some infected people have no symptoms but may still pass the parasite in their stool.

Common symptoms include:

• Frequent watery diarrhea
• Stomach pain or cramps
• Nausea or vomiting
• Reduced appetite and weight loss
• Mild fever
• Headache, weakness, or tiredness

The diarrhea is usually not bloody. Blood in your stool may have another cause and should be assessed.

Symptoms often last about one to two weeks in people with healthy immune systems. They may improve and then return before finally settling. In people with weakened immunity, diarrhea can continue for weeks or months and may be harder to control.

Children, older adults, and anyone with heavy fluid loss can become dehydrated more quickly. Signs include a dry mouth, strong thirst, dizziness, dark urine, or urinating less than usual.

Cryptosporidium enteritis occurs when you swallow the parasite. A very small amount may be enough to cause infection.

The parasite can spread through:

• Drinking untreated or contaminated water
• Swallowing water from pools, splash parks, lakes, or rivers
• Eating food handled by someone carrying the parasite
• Changing diapers or helping someone with toileting
• Contact with infected farm animals, pets, or animal waste
• Sexual contact involving exposure to stool

Anyone can get Crypto. Risk is higher among young children, childcare workers, household members of an infected person, swimmers, animal handlers, campers, and people who drink untreated water.

International travel may increase exposure where clean water and sanitation are limited. Outbreaks can also occur in childcare centres, households, swimming facilities, and communities with contaminated water supplies.

A weakened immune system raises the risk of prolonged or severe infection. This can occur with advanced HIV, certain cancers, immune-suppressing medicines, organ transplantation, or some inherited immune conditions. Do not stop prescribed immune-suppressing medicine on your own.

Symptoms alone cannot confirm Crypto because many infections and bowel conditions cause watery diarrhea.

Diagnosis is made by finding the parasite or its genetic material in a stool sample. Tests may include polymerase chain reaction, usually called PCR, antigen testing, or examination under a microscope.

PCR looks for genetic material from the parasite. It may be included in a panel that checks for several causes of infectious diarrhea at once.

Cryptosporidium may not appear in every sample. You may therefore be asked to provide stool samples collected on separate days. Tell the healthcare professional arranging the test about recent travel, swimming, animal contact, illness in your household, and any condition or medicine that weakens your immune system.

Blood tests do not usually confirm Crypto. They may be used to check dehydration, salt levels, kidney function, or the effects of prolonged illness.

Replacing lost fluid is the main treatment. Many people with healthy immune systems recover with supportive care while their immune system clears the infection.

Take frequent small drinks if nausea makes larger amounts difficult. Oral rehydration solutions contain water, sugar, and salts in proportions designed to replace diarrheal losses. Children and older adults may need closer monitoring because dehydration can develop quickly.

Severe dehydration may require fluids through a vein in hospital. Nutrition support may also be needed if prolonged diarrhea causes major weight loss or difficulty eating.

Nitazoxanide is an antiparasitic medicine used in some countries for Crypto-related diarrhea. In the United States, it is approved for certain people aged 1 year and older with healthy immune systems. Its benefit has not been clearly established in people with weakened immunity. Whether it is suitable depends on factors such as age, immune health, local approval, and test results.

For people with HIV, effective antiretroviral treatment can help the immune system control the infection. Other causes of immune suppression require specialist review. Any adjustment to transplant, cancer, or immune-suppressing treatment must be medically supervised.

Antibiotics like amoxicillin or doxycycline used for bacterial infections do not treat Crypto. Medicines that slow diarrhea are not suitable for everyone, particularly young children or people with fever, blood in the stool, or another possible infection. Seek advice before using them.

The most common complication is dehydration. Severe fluid loss can disturb the body’s salt balance and affect kidney function or blood pressure.

Prolonged infection may cause weight loss, poor nutrition, weakness, and difficulty absorbing nutrients. In children, a long illness can interfere with nutrition and growth.

People with severe immune suppression can develop ongoing diarrhea and major weight loss. Less commonly, the parasite may affect the gallbladder, bile ducts, pancreas, or breathing system. These complications need specialist care.

No vaccine is currently available. Infection cannot always be prevented, but careful hygiene and safer water practices reduce the chance of spreading it.

Wash your hands thoroughly with soap and running water after using the toilet, changing diapers, touching animals, and before preparing or eating food. Alcohol-based hand sanitiser does not reliably kill Cryptosporidium and should not replace handwashing.

Avoid swallowing water while swimming. Do not drink untreated water from lakes, rivers, springs, or shallow wells. During a water safety notice, follow local instructions about boiling or filtering water. Not every household filter removes Crypto; filters need to be specifically designed for parasite or cyst removal.

If you have diarrhea:

• Do not prepare food for other people
• Stay out of pools, splash parks, and other shared water
• Keep children with diarrhea out of childcare
• Clean bathroom surfaces and wash soiled laundry carefully
• Avoid sexual activity that could involve contact with stool

Because the parasite can remain in stool after symptoms stop, public health guidance recommends avoiding swimming for two weeks after the diarrhea has ended. Waiting two weeks before sexual activity also reduces the chance of passing it to a partner.

People with severely weakened immune systems may need extra precautions around drinking water, travel, young farm animals, and childcare settings.

Most people with healthy immune systems recover fully. Diarrhea commonly lasts one to two weeks, but symptoms may come and go for several weeks. Appetite, energy, and bowel habits can take additional time to return to normal.

During recovery, focus on fluids and foods you can tolerate. There is no single required “Crypto diet.” Smaller meals may be easier while nausea or cramps continue. Temporary difficulty digesting lactose, the sugar in milk, can occur after intestinal infections and may make diarrhea or bloating worse.

You may continue passing the parasite after you feel better. Handwashing and avoiding shared swimming water remain important during this period.

Long-term problems are uncommon after a short infection. The outlook is less predictable when the immune system is severely weakened. Symptoms may continue until immune function improves, and relapses can occur. Ongoing care then focuses on hydration, nutrition, symptom control, and treatment of the underlying immune problem.

Arrange prompt medical advice if diarrhea is persistent, keeps returning, or is causing weight loss. Testing is especially important if you have a weakened immune system, are pregnant, recently travelled, drank untreated water, or were part of a suspected outbreak.

Seek urgent medical care if you or a child:

• Cannot keep fluids down
• Is urinating much less than usual
• Has no wet diapers for an unusually long time
• Has a very dry mouth, no tears, or sunken eyes
• Becomes dizzy when standing
• Has severe or worsening abdominal pain
• Has blood or black material in the stool
• Has diarrhea with a significant or persistent fever

Call emergency services for fainting, confusion, difficulty waking, severe weakness, breathing difficulty, or almost no urine. These can be signs of severe dehydration or another serious condition.

Mild symptoms that are improving usually do not require emergency care. Routine follow-up may be needed to review test results, confirm that hydration and weight are recovering, or manage return-to-work and childcare requirements.

How long does Cryptosporidium diarrhea last?

In people with healthy immune systems, symptoms often last one to two weeks. They can improve and return before stopping. Illness may continue for weeks or months when the immune system is severely weakened.

Is Cryptosporidium contagious?

Yes. The parasite passes in stool and can spread through contaminated hands, food, water, surfaces, or sexual contact. Someone may continue passing it after the diarrhea has ended.

Can I go to work or school with Crypto?

Stay home while you have diarrhea. Food handlers, childcare workers, healthcare workers, and children in childcare may have additional local rules. A public health team or the organisation involved can explain when returning is appropriate.

Does chlorine kill Cryptosporidium in swimming pools?

Normal pool chlorine levels do not kill Crypto quickly. This is why outbreaks can occur in treated pools. Avoid all shared swimming water while ill and for two weeks after diarrhea stops.

Can Cryptosporidium come back?

Symptoms can come and go during the same infection. Reinfection is also possible because previous infection does not provide complete protection. Continued symptoms may need repeat testing or assessment for another cause.

Will antibiotics cure Crypto?

Standard antibiotics for bacterial infections do not treat Cryptosporidium. Nitazoxanide is an antiparasitic medicine that may be used for eligible people, but many infections clear with hydration and the body’s immune response.