From the Center for Disease Control and Prevention (CDC)
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.
Cryptosporidiosis (or “Crypto” for short) is a disease that causes watery diarrhea. It is caused by microscopic germs—parasites called Cryptosporidium. Although Crypto can affect all people, some groups are likely to develop more serious illness. For people with weakened immune systems, symptoms can be severe and could lead to severe or life-threatening illness. Examples of people with weakened immune systems include those with AIDS; those with inherited diseases that affect the immune system; and cancer and transplant patients who are taking certain immunosuppressive drugs.
Illness and symptoms
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
- Weight loss
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 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 and detection
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.
Sources of infection and risk factors
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
- 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.