Cyclosporiasis and Cryptosporidiosis

Cyclosporiasis (sy-klo-spor-I-a-sis) and Cryptosporidiosis (krip-to-spo-rid-e-O-sis) are infections in the intestines that result from eating or drinking food or water contaminated by the parasites Cyclospora cayetanensis and Cryptosporidium parvum. These infections can result in diarrhea, stomach cramps, and nausea.


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Thousands of people in Milwaukee, Wisconsin, started to get sick in early 1993. They had stomach pains, nausea, fever, and diarrhea, as if perhaps they had influenza. But authorities soon discovered that dangerous one-celled parasites * were in the city's water supply. When people drank water, the parasite caused cryptosporidiosis, one of several infections that parasites can cause.

In the end, more than 400,000 people came down with symptoms of cryptosporidiosis. More than 100 people died, including many who had other diseases like AIDS. The parasite had entered the water system from human waste in Lake Michigan, a water source for the city. Filters on the city's water plant had not removed the parasite. That problem has been remedied.

How Do People Get Cyclosporiasis
and Cryptosporidiosis?

Cryptosporidiosis and cyclosporiasis, a closely related illness, are two of the most common infections that result from contaminated water and food. They (and similar illnesses) affect millions of people worldwide and are especially dangerous to children, the elderly, and people with other illnesses, especially those (like AIDS) that weaken the immune system. The infections are common in developing nations, but they also are found increasingly in developed nations like the United States that import food. For example, a 1996 outbreak of cyclosporiasis in Houston, Texas, was linked with raspberries imported from Guatemala.

Both cyclosporiasis and cryptosporidiosis result when humans eat food or drink water containing microscopic parasites from infected human or animal waste. The Cyclospora cayetanensis and Cryptosporidium parvum parasites also can enter the human body when people touch objects that have come in contact with infected fecal matter and then place fingers in their mouths. Fresh fruits and vegetables can become contaminated if they are irrigated with water that contains the parasites.

* parasites are creatures that live in and feed on the bodies of other organisms. The animal or plant harboring the parasite is called its host.

What Happens When People Get Cyclosporiasis and


Although caused by different parasites, cyclosporiasis and cryptosporidiosis cause many of the same symptoms: watery diarrhea, stomach pain, nausea, fever, and vomiting. Weight loss is common, because of the diarrhea and loss of appetite. The first symptoms of cyclosporiasis often appear a week after the parasite enters the body, but the first symptoms of cryptosporidiosis may appear as soon as two days after infection or as long as ten days after. The illnesses can last for a few days to two weeks. Infections from cyclosporiasis sometimes can last more than a month and return one or more times.


It can be hard to diagnose cyclosporiasis and cryptosporidiosis, because many illnesses can cause similar symptoms. If doctors suspect these infections, they may order tests to examine patients' stool for signs of the parasites.


The danger of intestinal infections like cyclosporiasis and cryptosporidiosis is dehydration from the loss of water through diarrhea. Doctors will remind patients to drink plenty of fluids, like water and sports drinks. Cyclosporiasis also can be treated with antibiotics. Cryptosporidiosis, however, has no special drug cure. Usually people will completely recover from either illness in a week or two. People with AIDS and other diseases that weaken the immune system need extra medical attention, because they are at higher risk of severe infections.

How Are These Infections Prevented?

Intestinal infections like cyclosporiasis and cryptosporidiosis are among the most common illnesses in the world. Several activities can lower the chances of getting these or similar intestinal illnesses:

  • Washing hands frequently and thoroughly with hot water, especially after going to the bathroom, changing diapers, playing with animals or cleaning up after them, and gardening, because the soil can be contaminated by animal or human waste. It also is important to clean hands before eating.
  • Washing fresh fruits and vegetables thoroughly before eating. Even fruit that can be peeled should be washed.
  • Avoiding unfiltered water from lakes, rivers, and other sources. Even a sparkling spring might be contaminated and should not be used for drinking water. It also is important to avoid swallowing water in lakes and rivers as well as in swimming pools and spas, because chlorine might not be enough to kill the parasites.

Did You Know?

Intestinal infections like cyclosporiasis and cryptosporidiosis are among the most common illnesses in the world. More than 2.2 million people worldwide died from illnesses that cause severe diarrhea, making it the sixth leading cause of death in 1998. All but 7,000 of those deaths occurred in low-and middle-income nations.

Water quality varies, even in industrialized nations like the United States. Tap water led to the 1993 outbreak of cryptosporidiosis in Milwaukee. Some people choose to drink only bottled water or use special filters for drinking water and ice. When overseas, and especially when in developing nations, it is never a good idea to drink tap water or use ice made from tap water. It also is recommended that fruits and vegetables be avoided when traveling outside the United States, unless they can be cooked or peeled.

See also
Parasitic Diseases


The U.S. National Center for Infectious Diseases has a Division of Parasitic Diseases that posts fact sheets about cyclosporiasis and cryptosporidiosis at its website.

The U.S. Food and Drug Administration posts a Bad Bug Book at its website with fact sheets about Cyclospora cayetanensis, Cryptosporidium parvum, and other parasitic protozoa.

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