Cryptosporidiosis is an intestinal infection caused by Cryptosporidium, a protozoan parasite. The main symptoms are abdominal cramping and diarrhea.
People acquire the infection by consuming contaminated water or food or by having contact with infected people or animals.
Abdominal cramping and watery diarrhea may begin suddenly, sometimes accompanied by nausea, vomiting, fever, and weakness.
Doctors diagnose the infection by examining or analyzing a stool sample for signs of the parasite.
Adequate sanitation and hand washing can help prevent spread of the infection, as can boiling water before drinking it.
Healthy people often recover on their own, but they may require treatment with an antiparasitic drug.
People with AIDS or a weakened immune system may continue to have diarrhea even after they have been treated with an antiparasitic drug.
(See also Overview of Parasitic Infections.)
Cryptosporidium parasites are protozoa that infect people and many kinds of animals throughout the world.
Cryptosporidiosis is acquired by
Ingesting Cryptosporidium parasites in water or food contaminated by human or animal feces containing the parasite's eggs
Ingesting parasites from soil or an item that has been contaminated with eggs
Ingesting parasites acquired from close contact with an infected person or animal
The thick-walled eggs of Cryptosporidium are very hardy and are frequently present in swimming pools, hot tubes, water parks, lakes, and rivers around the world. The parasite is not killed by freezing or by the usual levels of chlorine in swimming pools or drinking water.
After people swallow the eggs, the eggs move to the intestine, where they release an immature form of the parasite, which enters the cells that line the intestine. The parasite matures, multiplies, and produces eggs. People then pass the eggs in their feces. Only a small number of Cryptosporidium eggs are required to cause infection. Because of the enormous number of Cryptosporidium that an infected person or animal can shed (10 million to 100 million) in their stool and the ability of just a few ingested organisms to start an infection, the infection can easily spread person-to-person, for example, in day care centers or petting zoos.
Image from the Centers for Disease Control and Prevention, Global Health, Division of Parasitic Diseases and Malaria.
Cryptosporidiosis is a common cause of diarrhea among children living in areas where sanitation is poor. It occasionally occurs among travelers to such areas. Cryptosporidiosis also causes diarrhea outbreaks in the United States. In Baker City, Oregon, 2,780 people became sick when the city's water supply was contaminated with Cryptosporidium in 2013. Outbreaks have occurred in other cities and in day care centers.
People with a weakened immune system, particularly those with advanced AIDS, are prone to cryptosporidiosis and are more likely to have severe, persistent disease.
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Symptoms of Cryptosporidiosis
Cryptosporidiosis symptoms may begin abruptly about 7 days after people are infected and consist mainly of abdominal cramps and watery diarrhea. Nausea, vomiting, loss of appetite, fever, and weakness may also occur. Symptoms usually last 1 to 2 weeks, then subside. People may pass eggs in their stool for several weeks after symptoms have disappeared.
In people with a weakened immune system, symptoms of cryptosporidiosis may begin gradually, and the diarrhea can vary from mild to severe (as much as 3 to 4 gallons [11 to 15 liters] of watery stool per day in people with AIDS) and may persist for a long time.
Cryptosporidiosis is also associated with undernutrition in children living in areas with poor sanitation.
Diagnosis of Cryptosporidiosis
Stool tests
To diagnose cryptosporidiosis, a doctor sends a stool sample to be tested for a protein released by the parasite (antigen testing) or for the parasite's genetic material (DNA).
Another approach is to examine stool under a microscope for Cryptosporidium eggs, but this method is less sensitive, and several stool samples may be needed to find the parasite. Specialized techniques can be used to increase the chances of identifying the eggs.
Doctors may use a flexible viewing tube (endoscope) to examine the upper part of digestive tract, including the first part of the small intestine (duodenum), when diagnostic tests of stool do not identify a cause for persistent diarrhea. Doctors may use this procedure to obtain a sample of tissue to be examined and analyzed (biopsied). Cryptosporidium, if present, can be seen in a biopsy sample from the intestine.
Prevention of Cryptosporidiosis
Cryptosporidiosis prevention involves adequate sanitation and hand washing, particularly in health care facilities and day care centers and after contact with soil, animals, or infected people. People should not drink or swallow water that could be contaminated, such as that from a swimming pool, hot tub, water park, stream, river, lake or ocean, or tap water during international travel to areas where sanitation is poor. Safer sex practices are important in preventing infection from anal contact.
When public health departments discover a localized outbreak of the disease, they typically advise people to
Boil drinking water (including water for toothbrushing and food washing)
Eat only cooked foods
Avoid unpasteurized milk and juice
Tap water filters that use reverse osmosis or have the words "tested and certified by NSF/ANSI Standard No. 53 or No. 58 for cyst removal/reduction" are likely to be effective. Other types of filters may not be.
Treatment of Cryptosporidiosis
For people with a normal immune system
For people with AIDS
If diarrhea is severe, fluids and an antidiarrheal drug
People with a healthy immune system
people who have AIDS. The most important therapy is to treat the HIV infection
Select Medical Literature
1. Gharpure R, Perez A, Miller AD, et al: Cryptosporidiosis Outbreaks—United States, 2009-2017. MMWR Morb Mortal Wkly Rep 68:568-72, 2019.
2. Pantenburg B, Cabada MM, White AC Jr: Treatment of cryptosporidiosis. Expert Rev Anti Infect Ther 7(4):385-91, 2009. doi: 10.1586/eri.09.24
