What Is Cryptosporidium, and Should You Be Concerned?

Consider this before you dive in: Cryptosporidium is the leading cause of waterborne illness. REUTERS/Leonhard Foeger

In recent weeks, public health officials have issued warnings about the potential health hazards of Cryptosporidium, a tiny parasite found frequently in swimming pools and other recreational waters. This nasty germ causes a short-lived but very unpleasant stomach illness guaranteed to put a damper on summer fun.

What is crypto?

Crypto is a microscopic protozoan parasite that is the leading cause of waterborne illness in the U.S. It is also found in contaminated food and water.

There are more than 20 different species of Cryptosporidium, but only a few are known to cause illness in humans. Like toxoplasma gondii, the parasite is protected by an outer shell that allows it to live for weeks without a human or animal host.

How do you get it?

The parasite is spread through contact with feces from infected humans and animals. According to the U.S. Centers for Disease Control and Prevention, a person with crypto sheds as many as 10 million to 100 million crypto spores in a single bowel movement. The odds are against us homo sapiens, since a healthy person can become sick by ingesting as few as 10 crypto spores. The parasite will then make a temporary home in the small intestines and start to multiply.

Crypto can potentially survive outside of a human and animal host for weeks and is often resistant to antibacterial cleaners and disinfectants. This includes chlorine, the chemical most commonly used to keep public swimming pools and Jacuzzis hygienic. Swallowing water in swimming pools, lakes or rivers that harbor the parasite can cause a person to become infected. Crypto is also transmitted by ingesting raw or uncooked food and beverages that contain the parasite. The parasite can also be transmitted through food preparation by someone with unwashed hands.

What are the symptoms?

Crypto causes cryptosporidiosis, a nasty gastrointestinal illness with symptoms that include stomach cramping, nausea, vomiting, fever and watery diarrhea (an illness generally known as gastroenteritis). Symptoms usually begin two to seven days after infection. The illness can lead to dehydration and weight loss, and may last anywhere from as little as four days to as long as two weeks. Some people with crypto don't actually develop any symptoms but can potentially still transmit the illness to others through close contact.

How many people contract crypto each year?

According to the CDC, there were 9,313 cryptosporidiosis cases in 2011.

Who is at highest risk?

Anyone who frequently swims in recreational water—such as pools, lakes and rivers—is at risk for coming into contact with crypto. Parents and other people caring for children or infants infected with the parasite should remain hypervigilant about washing thoroughly after handling soiled linens and clothing or changing diapers. International travelers and hikers should stick with filtered or bottled water since crypto is often found in tap water in less developed countries.

Young children, pregnant women and people with compromised immune systems are at highest risk for becoming seriously ill from crypto.

How is crypto treated?

Most people recover from cryptosporidiosis without any treatment; the parasite just needs to run its course. It's important to remember to drink plenty of fluids since dehydration is one risk factor from cryptosporidiosis. Severe dehydration can result in hospitalization. People are advised to eat bland foods and drink plenty of fluids while recovering from the acute illness.

In certain instances, a physician may prescribe a five-day course of nitazoxanide, an antidiarrheal drug approved by the U.S. Food and Drug Administration to treat crypto infections.

How can you prevent an infection?

To reduce the risk for cryptosporidiosis stay away from public pools, Jacuzzis and lakes. Other unpleasant pathogens like the bacterial microorganism Vibrio vulnificus also lurks in these types of recreational waters. If you are going to go swimming, make sure you don't swallow the water.

Also, be a socially responsible swimmer: If you're recovering from a gastrointestinal illness wait several days before hopping into the pool to avoid passing on an infection to others.