Cryptosporidium is a microscopic parasite that causes the diarrheal disease cryptosporidiosis. Both the parasite and the disease are commonly known as “Crypto.”

There are many species of Cryptosporidium that infect animals, some of which also infect humans. The parasite is protected by an outer shell that allows it to survive outside the body for long periods of time and makes it very tolerant to chlorine disinfection.

While this parasite can be spread in several different ways, water (drinking water and recreational water) is the most common way to spread the parasite. Cryptosporidium is a leading cause of waterborne disease among humans in the United States.

What is cryptosporidiosis?

Cryptosporidiosis is a contagious disease that causes watery diarrhea. It is caused by parasites called Cryptosporidium, or Crypto . These parasites live in soil, food, and water. They are found in every region of the United States and throughout the world. Crypto can also be found on surfaces or dirty hands that have been contaminated with the stool (poop) of humans or animals that have the infection.

How is cryptosporidiosis spread?

You can become infected with Crypto by swallowing the parasite if it is in your food, drinking water, or water that you swim in. You can also get infected when you touch something that has been contaminated, and then you touch your eyes, mouth, or nose. Another way that Crypto can spread is through sexual contact.

Who is more likely to get cryptosporidiosis?

Certain people are more likely to get Crypto; they include:

• Children and workers at childcare centers
• Older adults (ages 75 years and older)
• People who take care of other people with Crypto
• International travelers
• Backpackers, hikers, and campers who drink unfiltered, untreated water
• People, including swimmers, who swallow water from contaminated sources
• People who touch infected animals, often cows or sheep

What are the symptoms of cryptosporidiosis?

The most common symptom of cryptosporidiosis is watery diarrhea. Other symptoms include:

• Dehydration
• Weight loss
• Stomach cramps or pain
• Fever
• Nausea and vomiting

The symptoms generally begin 2 to 10 days after becoming infected with the parasite. In people with healthy immune systems, the symptoms can last about 1 to 2 weeks. Occasionally, the symptoms can last longer or come and go for up to 30 days.

People with weakened immune systems may develop a serious, chronic illness. Some reasons why you might have a weakened immune system could include:

• Having HIV
• Having cancer
• Having a genetic condition that affects the immune system
• Taking certain medicines, such as chemotherapy and medicines needed after an organ transplant

Some people may not have any symptoms at all.

Contact your health care provider if you have watery diarrhea that lasts more than a few days, especially if you have a weakened immune system.

How is cryptosporidiosis diagnosed?

Cryptosporidiosis is diagnosed by examining stool samples, usually under a microscope. People with Crypto can have many parasites in their stool one day but not as many the next day. So you may need to give the lab three stool samples collected on three different days. This helps make sure that your diagnosis is correct.

What are the treatments for cryptosporidiosis?

Most people with cryptosporidiosis get better without treatment. It usually takes about one to two weeks. It's important to drink plenty of fluids to prevent dehydration. Infants, young children, and pregnant people are more likely to get dehydration. They should get extra fluids. If you are pregnant or if you think that you or your child are severely dehydrated, contact your provider about how to get enough fluids. Some people who are dehydrated may need to get intravenous (IV) fluids in a hospital.

Over-the-counter anti-diarrheal medicine might help slow down diarrhea, but do not take it without first asking your provider. There is a medicine to treat diarrhea caused by Crypto in people with healthy immune systems. You and your provider can talk about whether that medicine is right for you.

Can cryptosporidiosis be prevented?

To lower your chance of getting or spreading Crypto:

• Wash your hands often with soap and water, especially after using the toilet, changing diapers, or touching animals. You also need to wash your hands before eating or preparing food. Alcohol-based hand sanitizers are not effective against Crypto.
• Only drink water that you know is safe.
• Only drink milk and apple cider that have been pasteurized.
• Don't eat uncooked foods when traveling in countries where the food supply might be unsafe.
• Never go swimming when you have diarrhea.
• Don't swallow water when you go swimming.
• Use condoms or dental dams every time you have sex. This will also help prevent other sexually transmitted infections.

Causal Agent:

Many species of Cryptosporidium exist that infect humans and a wide range of animals. Although Cryptosporidium parvum and Cryptosporidium hominis (formerly known as C. parvum anthroponotic genotype or genotype 1) are the most prevalent species causing disease in humans, infections by C. felis, C. meleagridis, C. canis, and C. muris have also been reported.

Life Cycle

Sporulated oocysts, containing 4 sporozoites, are excreted by the infected host through feces and possibly other routes such as respiratory secretions (1). Transmission of Cryptosporidium parvum and C. hominis occurs mainly through contact with contaminated water (e.g., drinking or recreational water). Occasionally food sources, such as chicken salad, may serve as vehicles for transmission. Many outbreaks in the United States have occurred in waterparks, community swimming pools, and day care centers. Zoonotic and anthroponotic transmission of C. parvum and anthroponotic transmission of C. hominis occur through exposure to infected animals or exposure to water contaminated by feces of infected animals (2). Following ingestion (and possibly inhalation) by a suitable host (3), excystation (a) occurs. The sporozoites are released and parasitize epithelial cells (b, c) of the gastrointestinal tract or other tissues such as the respiratory tract. In these cells, the parasites undergo asexual multiplication (schizogony or merogony) (d, e, f) and then sexual multiplication (gametogony) producing microgamonts (male) (g) and macrogamonts (female) (h). Upon fertilization of the macrogamonts by the microgametes (i), oocysts (j, k) develop that sporulate in the infected host. Two different types of oocysts are produced, the thick-walled, which is commonly excreted from the host (j), and the thin-walled oocyst (k), which is primarily involved in autoinfection. Oocysts are infective upon excretion, thus permitting direct and immediate fecal-oral transmission.

Crypto lives in the intestine of infected humans or animals. An infected person or animal sheds Cryptosporidium parasites in the stool. Millions of Crypto parasites can be released in a bowel movement from an infected human or animal. Shedding begins when the symptoms begin and can last for weeks after the symptoms (e.g., diarrhea) stop. You can become infected after accidentally swallowing the parasite. Crypto may be found in soil, food, water, or surfaces that have been contaminated with the feces from infected humans or animals. Crypto is not spread by contact with blood. Crypto can be spread by:

• Putting something in your mouth or accidentally swallowing something that has come in contact with the stool of a person or animal infected with Crypto.
• Swallowing recreational water contaminated with Crypto. Recreational water can be contaminated with sewage or feces from humans or animals.
• Swallowing water or beverages contaminated by stool from infected humans or animals.
• Eating uncooked food contaminated with Crypto. All fruits and vegetables you plan to eat raw should be thoroughly washed with uncontaminated water.
• Touching your mouth with contaminated hands. Hands can become contaminated through a variety of activities, such as:
  • touching surfaces (e.g., toys, bathroom fixtures, changing tables, diaper pails) that have been contaminated by stool from an infected person,
  • changing diapers,
  • caring for an infected person, and
  • handling an infected animal such as a cow or calf.

People with greater exposure to contaminated materials are more at risk for infection, such as:

• Children who attend childcare centers, including diaper-aged children
• Childcare workers
• Parents of infected children
• Older adults (ages 75 years and older)
• People who take care of other people with cryptosporidiosis
• International travelers
• Backpackers, hikers, and campers who drink unfiltered, untreated water
• People who drink from untreated shallow, unprotected wells
• People, including swimmers, who swallow water from contaminated sources
• People who handle infected cattle
• People exposed to human feces through sexual contact

Contaminated water may include water that has not been boiled or filtered, as well as contaminated recreational water sources. Several community-wide outbreaks of cryptosporidiosis have been linked to drinking municipal water or recreational water contaminated with Cryptosporidium.

Cryptosporidium parasites are found in every region of the United States and throughout the world. Travelers to developing countries may be at greater risk for infection because of poorer water treatment and food sanitation, but cryptosporidiosis occurs worldwide. In the United States, an estimated 748,000 cases of cryptosporidiosis occur each year .

Once infected, people with decreased immunity are most at risk for severe disease. The risk of developing severe disease may differ depending on each person’s degree of immune suppression.

Symptoms of cryptosporidiosis generally begin 2 to 10 days (average 7 days) after becoming infected with the parasite. The most common symptom of cryptosporidiosis is watery diarrhea. Symptoms include:

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

Some people with Crypto will have no symptoms at all.

Symptoms usually last about 1 to 2 weeks (with a range of a few days to 4 or more weeks) in persons with healthy immune systems. Occasionally, people may experience a recurrence of symptoms after a brief period of recovery before the illness ends. Symptoms can come and go for up to 30 days.

While the small intestine is the site most commonly affected, in immunocompromised persons Cryptosporidium infections could possibly affect other areas of the digestive tract or the respiratory tract.

People with weakened immune systems may develop serious, chronic, and sometimes fatal illness. Examples of people with weakened immune systems include:

• people with HIV/AIDS;
• those with inherited diseases that affect the immune system; and
• cancer and transplant patients who are taking certain immunosuppressive drugs.

The risk of developing severe disease may differ depending on each person’s degree of immune suppression.

Diagnosis of cryptosporidiosis is made by examination of stool samples. Because detection of Cryptosporidium can be difficult, patients may be asked to submit several stool samples over several days. Most often, stool specimens are examined microscopically using different techniques (e.g., acid-fast staining, direct fluorescent antibody [DFA] , and/or enzyme immunoassays for detection of Cryptosporidium sp. antigens).

Molecular methods (e.g., polymerase chain reaction – PCR) are increasingly used in reference diagnostic labs, since they can be used to identify Cryptosporidium at the species level. Tests for Cryptosporidium are not routinely done in most laboratories; therefore, healthcare providers should specifically request testing for this parasite.

Most people who have healthy immune systems will recover without treatment. Diarrhea can be managed by drinking plenty of fluids to prevent dehydration. People who are in poor health or who have weakened immune systems are at higher risk for more severe and prolonged illness. Young children and pregnant women may be more susceptible to dehydration resulting from diarrhea and should drink plenty of fluids while ill. Rapid loss of fluids from diarrhea may be especially life threatening to babies. Therefore, parents should talk to their healthcare providers about fluid replacement therapy options for infants.

Anti-diarrheal medicine may help slow down diarrhea, but a healthcare provider should be consulted before such medicine is taken. Nitazoxanide has been FDA-approved for treatment of diarrhea caused by Cryptosporidium in people with healthy immune systems and is available by prescription. However, the effectiveness of nitazoxanide in immunosuppressed individuals is unclear.

HIV-positive individuals who suspect they have cryptosporidiosis should contact their healthcare provider. For those persons with HIV/AIDS, anti-retroviral therapy that improves the immune status will also decrease or eliminate symptoms of cryptosporidiosis. However, even if symptoms disappear, cryptosporidiosis is often not curable and the symptoms may return if the immune status worsens.

Is there a treatment for diarrhea caused by Cryptosporidium?

Yes. FDA licensed nitazoxanide (Alinia®, Romark Laboratories, Tampa, FL, USA) for treatment of cryptosporidiosis in children aged 1-11 years in November 2002. In June 2004, nitazoxanide was also licensed for older children and adults. It can now be prescribed for all patients ≥ 1 year of age.

What age groups can be treated with nitazoxanide?

In 2004, the FDA licensed nitazoxanide for all persons ≥ 1 year of age. It had previously been licensed in 2002 for only children aged 1-11 years.

What is the dosage used for nitazoxanide?

Nitazoxanide oral suspension (100 mg/5ml; patients ≥ 1 year of age) and Nitazoxanide tablets (500 mg; patients ≥ 12 years of age) are indicated for the treatment of diarrhea caused by Cryptosporidium.

What is the efficacy?

Clinical cure (resolution of diarrhea) rates range from 72-88% . Parasitologic cure (no Cryptosporidium detected in stool) rates range from 60-75% . Parasitologic cure rate was a key consideration in developing prevention recommendations that ask people to refrain from swimming for 2 weeks after resolution of symptoms. Retesting of treated persons is not considered necessary.

How rapidly does the drug work?

It may take up to 5 days for diarrhea to resolve in approximately 80% of patients . Because of this and the lower parasitologic cure rate, CDC still recommends that all infected persons, including those who have completed treatment, do not swim for 2 weeks after resolution of symptoms. It is critical that this recommendation is followed to prevent the spread of this chlorine-resistant parasite through public swimming pools and other aquatics venues.

Should patients be re-tested after treatment with nitazoxanide and, if so, when?

Healthcare professionals might consider re-testing stool at least 1 week after the last dose of nitazoxanide only if symptoms do not resolve. In such cases, longer courses of treatment might be needed. Persistent symptoms may also represent re-infection or other causes of illness besides cryptosporidiosis.

My patient is still ill. What other treatment regimens have been tried?

Nitazoxanide appears to be well tolerated and different treatment regimens have been used for a variety of infections. Immunocompetent persons with cryptosporidiosis have been treated with multiple 3-day courses of nitazoxanide . Seven-day courses have also been used in early studies for cryptosporidiosis and other parasitic infections . AIDS patients with Cryptosporidium-associated diarrhea received the drug for 28 days.

What about patients with compromised immune systems?

Nitazoxanide has been approved for treatment of diarrhea caused by Cryptosporidium in people with healthy immune systems. It is presently not approved to treat immunodeficient persons because nitazoxanide oral suspension and nitazoxanide tablets have not been shown to be superior to placebo for the treatment of diarrhea caused by Cryptosporidium in HIV-infected or immunodeficient patients.

What should I tell my patients with cryptosporidiosis about swimming?

Cryptosporidium now causes over half of the reported waterborne disease outbreaks associated with swimming in chlorinated public swimming pools . Cryptosporidium’s chlorine resistance and documented excretion for weeks after resolution of symptoms has led CDC and The American Academy of Pediatrics to recommend that all persons refrain from swimming until 2 weeks after resolution of symptoms.

The following recommendations are intended to help prevent and control cryptosporidiosis (or “Crypto” for short) in members of the general public. For recommendations for immunocompromised persons, please see Prevention & Control – Immunocompromised Persons.

Practice Good Hygiene Everywhere

• Help keep yourself and your loved ones healthy by washing your hands often with soap and water, especially during key times when you are likely to spread germs.

• Alcohol-based hand sanitizers are not effective against Crypto. Washing hands at key times with soap and water can help prevent infections.

At childcare facilities

• Exclude children who are sick with diarrhea from childcare settings until the diarrhea has stopped.
• Clean, sanitize, or disinfect toys and surfaces to prevent germs from spreading easily.
• Wash hands regularly with soap and water to keep kids and caregivers healthy.
• Move adults with diarrhea to jobs that minimize opportunities for spreading Crypto (for example, to administrative work instead of food or drink preparation).

At the pool, lake, and other places we swim

• Do not swim or let kids swim if sick with diarrhea.
  • If crypto is diagnosed, wait 2 weeks after diarrhea has stopped to go swimming.
• Do not swallow the water.
• Take young children on bathroom breaks or check their diapers every 60 minutes.
  • Change diapers in a bathroom or diaper-changing area—not waterside—to keep germs and poop out of the water.

Avoid Water That Might Be Contaminated

• Do not drink untreated water or use untreated ice from lakes, rivers, springs, ponds, streams, or shallow wells.
• Follow advice given during local drinking water advisories.
• If the safety of the drinking water is in doubt (for example, if water source is unknown), use at least one of the following:
  • Commercially bottled water
  • Water that has been previously boiled for at least 1 minute and left to cool. At elevations above 6,500 feet (1,981 meters), boil for 3 minutes.
  • A filter designed to remove Crypto.
    • The label might read ‘NSF 53’ or ‘NSF 58.’
    • Filter labels that read “absolute pore size of 1 micron or smaller” are also effective.

Avoid Food That Might Be Contaminated

• If you drink milk or apple cider, only buy if it has been pasteurized.
• Do not eat fruits and vegetables washed in water that might be contaminated.

Practice Extra Caution While Traveling

• Do not use or drink inadequately treated water or use ice when traveling in countries where the water might be unsafe.
• Avoid eating uncooked foods when traveling in countries where the food supply might be unsafe.

Practice Safer Sex

• Wait to have sex (vaginal, anal, and oral) for 2 weeks after you no longer have diarrhea. Patients typically stop having Crypto in their poop within 2 weeks after symptoms completely stop.
• Reduce your contact with poop during sex by:
  • Washing your hands, genitals, and anus with soap and water before and after sexual activity.
  • Using barrier methods during sex. Barrier methods include condoms, dental dams, and cut-open condoms. Sex includes oral (mouth-to-penis, mouth-to-vagina, mouth-to-anus), anal (penis-to-anus), and vaginal (penis-to-vagina) sex. Using latex gloves during anal fingering or fisting.
  • Using condoms the right way, every time you have anal and vaginal sex, which will also help prevent other sexually transmitted infections.
  • Washing your hands with soap and water immediately after touching a used condom or other barrier method.
  • Washing sex toys with soap and water after each use, and washing hands after touching used sex toys.

What is cryptosporidiosis?

Cryptosporidiosis is a disease that causes watery diarrhea. It is caused by microscopic germs—parasites called Cryptosporidium. Cryptosporidium, or “Crypto” for short, can be found in water, food, soil or on surfaces or dirty hands that have been contaminated with the feces of humans or animals infected with the parasite. During 2001–2010, Crypto was the leading cause of waterborne disease outbreaks, linked to recreational water in the United States. The parasite is found in every region of the United States and throughout the world.

How is cryptosporidiosis spread?

Crypto lives in the gut of infected humans or animals. An infected person or animal sheds Crypto parasites in their poop. An infected person can shed 10,000,000 to 100,000,000 Crypto germs in a single bowel movement. Shedding of Crypto in poop begins when symptoms like diarrhea begin and can last for weeks after symptoms stop. Swallowing as few as 10 Crypto germs can cause infection.

Crypto can be spread by:

• Swallowing recreational water (for example, the water in swimming pools, fountains, lakes, rivers) contaminated with Crypto
  • Crypto’s high tolerance to chlorine enables the parasite to survive for long periods of time in chlorinated drinking and swimming pool water
• Drinking untreated water from a lake or river that is contaminated with Crypto
• Swallowing water, ice, or beverages contaminated with poop from infected humans or animals
• Eating undercooked food or drinking unpasteurized/raw apple cider or milk that gets contaminated with Crypto
• Touching your mouth with contaminated hands
  • Hands can become contaminated through a variety of activities, such as touching surfaces or objects (e.g., toys, bathroom fixtures, changing tables, diaper pails) that have been contaminated by poop from an infected person, changing diapers, caring for an infected person, and touching an infected animal
• Exposure to poop from an infected person through oral-anal sexual contact

Crypto is not spread through contact with blood.

What are the symptoms of cryptosporidiosis, when do they begin, and how long do they last?

Symptoms of Crypto generally begin 2 to 10 days (average 7 days) after becoming infected with the parasite. Symptoms include:

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

Symptoms usually last about 1 to 2 weeks (with a range of a few days to 4 or more weeks) in people with healthy immune systems.

The most common symptom of cryptosporidiosis is watery diarrhea. Some people with Crypto will have no symptoms at all.

Who is most at risk for cryptosporidiosis?

People who are most likely to become infected with Cryptosporidium include :

• Children who attend childcare centers, including diaper-aged children
• Childcare workers
• Parents of infected children
• Older adults (ages 75 years and older)
• People who take care of other people with Crypto
• International travelers
• Backpackers, hikers, and campers who drink unfiltered, untreated water
• People who drink from untreated shallow, unprotected wells
• People, including swimmers, who swallow water from contaminated sources
• People who handle infected calves or other ruminants like sheep
• People exposed to human poop through sexual contact

Contaminated water might include water that has not been boiled or filtered, as well as contaminated recreational water sources (e.g., swimming pools, lakes, rivers, ponds, and streams). Several community-wide outbreaks have been linked to drinking tap water or recreational water contaminated with Cryptosporidium. Crypto’s high tolerance to chlorine enables the parasite to survive for long periods of time in chlorinated drinking and swimming pool water. This means anyone swallowing contaminated water could get ill.

Note: Although Crypto can infect all people, some groups are likely to develop more serious illness.

• Young children and pregnant women may be more likely to get dehydrated because of their diarrhea so they should drink plenty of fluids while ill.
• People with severely weakened immune systems are at risk for more serious disease. Symptoms may be more severe and could lead to serious or life-threatening illness. Examples of people with weakened immune systems include those with HIV/AIDS; those with inherited diseases that affect the immune system; and cancer and transplant patients who are taking certain immunosuppressive drugs.

What should I do if I think I might have cryptosporidiosis?

For diarrhea whose cause has not been determined, the following actions may help relieve symptoms:

• Drink plenty of fluids to remain well hydrated and avoid dehydration. Serious health problems can occur if the body does not maintain proper fluid levels. For some people, diarrhea can be severe resulting in hospitalization due to dehydration.
• Maintain a well-balanced diet. Doing so may help speed recovery.
• Avoid beverages that contain caffeine, such as tea, coffee, and many soft drinks.
• Avoid alcohol, as it can lead to dehydration.

Contact your healthcare provider if you suspect that you have cryptosporidiosis.

How is cryptosporidiosis diagnosed?

Cryptosporidiosis is a diarrheal disease that is spread through contact with the stool of an infected person or animal. The disease is diagnosed by examining stool samples. People infected with Crypto can shed the parasite irregularly in their poop (for example, one day they shed parasite, the next day they don’t, the third day they do) so patients may need to give three samples collected on three different days to help make sure that a negative test result is accurate and really means they do not have Crypto. Healthcare providers should specifically request testing for Crypto. Routine ova and parasite testing does not normally include Crypto testing.

What is the treatment for cryptosporidiosis?

Most people with healthy immune systems will recover from cryptosporidiosis without treatment. The following actions may help relieve symptoms:

• Drink plenty of fluids to remain well hydrated and avoid dehydration. Serious health problems can occur if the body does not maintain proper fluid levels. For some people, diarrhea can be severe resulting in hospitalization due to dehydration.
• Maintain a well-balanced diet. Doing so may help speed recovery.
• Avoid beverages that contain caffeine, such as tea, coffee, and many soft drinks.
• Avoid alcohol, as it can lead to dehydration.

Over-the-counter anti-diarrheal medicine might help slow down diarrhea, but a healthcare provider should be consulted before such medicine is taken.

A drug called nitazoxanide has been FDA-approved for treatment of diarrhea caused by Cryptosporidium in people with healthy immune systems and is available by prescription. Consult with your healthcare provider for more information about potential advantages and disadvantages of taking nitazoxanide.

Individuals who have health concerns should talk to their healthcare provider.

Note: Infants, young children, and pregnant women may be more likely than others to suffer from dehydration. Losing a lot of fluids from diarrhea can be dangerous—and especially life-threatening in infants. These people should drink extra fluids when they are sick. Severe dehydration may require hospitalization for treatment with fluids given through your vein (intravenous or IV fluids). If you are pregnant or a parent and you suspect you or your child are severely dehydrated, contact a healthcare provider about fluid replacement options.

How should I clean my house to help prevent the spread of cryptosporidiosis?

No cleaning method is guaranteed to be completely effective against Crypto. However, you can lower the chance of spreading Crypto by taking the following precautions:

• Wash linens, clothing, dishwasher- or dryer-safe soft toys, etc. soiled with poop or vomit as soon as possible.
  • Flush excess vomit or poop on clothes or objects down the toilet.
  • Use laundry detergent, and wash in hot water: 113°F or hotter for at least 20 minutes or at 122°F or hotter for at least 5 minutes.
  • Machine dry on the highest heat setting.
• For other household object and surfaces (for example, diaper-change areas):
  • Remove all visible poop.
  • Clean with soap and water.
  • Let dry completely for at least 4 hours.
    • If possible, expose to direct sunlight during the 4 hours.
• Wash your hands with soap and water after cleaning objects or surfaces that could be contaminated with Crypto.

Note: The best way to prevent the spread of Cryptosporidium in the home is by practicing good hygiene. Wash your hands frequently with soap and water, especially after using the toilet, after changing diapers, and before eating or preparing food. Alcohol-based hand sanitizers are not effective against Crypto.