What is it? Cryptosporidium, commonly known as “Crypto,” is a protozoan parasite that can live in human and animal intestines. Only the species Cryptosporidium parvum is known to cause infection in humans.

Why is it dangerous/what is its effect on bathers? A strong outer shell, called an “oocyst,” makes Crypto highly resistant to the levels of sanitizer commonly found in a pool. In some cases, it may take as long as six or seven days in a properly sanitized and filtered pool for Crypto to be completely killed.
Two to ten days after accidental ingestion of Crypto, a disease called “cryptosporidiosis” may develop. Symptoms include diarrhea, upset stomach, cramps and fever. Some who ingest Crypto may not get sick; nonetheless, they may still carry and transmit the parasite. People with weakened immune systems, including HIV, chemotherapy and transplant patients, will have a much harder time recovering from illness. Small children and pregnant women can quickly become dehydrated.

How can it get into pool water? Transmission occurs through introduction of fecal matter into poorly treated pool water. Although young, nontoilet-trained children are the most common culprits, fecal contamination can occur through deposit of fecal droppings from animals, rodents and birds; guests or staff tracking fecal matter into the pool from adjoining landscaping; supply water taken from contaminated ground water, reservoirs or wells; rain and storm water run-off; and illegal cross-connections between pool circulation and sewage systems.

How can you safeguard your pool against it? To protect your pool, maintain proper, recommended sanitation levels. In addition, make it clear that people who have experienced any symptoms of diarrhea within the past two weeks should not enter the pool. Require the wearing of swimsuit diapers or tightfitting rubber or plastic pants by children not yet toilet trained. Post signs that ask patrons to shower before entering the pool.

What are some indications that it’s in your water? There are no good, consistent indications that Crypto is present in your pool. Any suggestion of fecal contamination should be treated immediately, as this could lead to possible infection.

How can you test for it? A general bacteria test can best ascertain the presence of Crypto. Although no simple test exists that specifically targets Crypto, a total bacteria test will alert you to any infiltration of harmful bacteria in your water. State and private laboratory facilities can test for the presence of Crypto. By the time you suspect Crypto, however it will most likely be dead.

If present, how do you remove it from pool water? Remove any visible fecal debris and superchlorinate the water. Keep swimmers out of the water for at least 30 minutes. If loose, watery stools are found in the water, close the pool, create a concentration-over-time (CT) value of 9,600, turn over the pool three or four times, dechlorinate the pool and restore water balance before reopening.

How do you treat cryptosporidium? There’s no commonly advised specific treatment for cryptosporidiosis, and recovery usually depends on the health of your immune system. Most healthy people recover within two weeks without medical attention.

If you have a compromised immune system, the illness can last and lead to significant malnutrition and wasting. The goal of treatment is to alleviate symptoms and improve your immune response. Cryptosporidiosis treatment options include:

  • Anti-parasitic drugs. Medications, such as nitazoxanide (Alinia), can help alleviate diarrhea by attacking the metabolic processes of the cryptosporidium organisms. Azithromycin (Zithromax) may be given along with one of these medications in people with compromised immune systems.
  • Anti-motility agents. These medications slow down the movements of your intestines and increase fluid absorption to relieve diarrhea and restore normal stools. Anti-motility drugs include loperamide and its derivatives (Imodium A-D, others). Talk with your doctor before taking any of these medications.
  • Fluid replacement. You’ll need either oral or intravenous replacement of fluids and electrolytes — minerals, such as sodium, potassium and calcium, that maintain the balance of fluids in your body — lost to persistent diarrhea. These precautions will help keep your body hydrated and functioning properly.
  • Antiretroviral therapies. If you have HIV/AIDS, highly active antiretroviral therapy (HAART) can reduce the viral load in your body and boost your immune response. Restoring your immune system to a certain level may completely resolve symptoms of cryptosporidiosis.


References: Aquatic Council, Mayo Clinic