Parasite That Causes Major Outbreaks Is Immune To Chlorine

Have you had a bout of the stomach flu lately? Are you a fan of the pool? What those two questions have in common is a chlorine-resistant parasite that have been on the rise. Cryptosporidium is behind an illness that can leave you with pain for days.

The parasite Cryptosporidium, or as it’s more often called Crypto has been behind several outbreaks the past few summers. Last year more than 2,000 people in Utah were attacked by the parasite during a state wide outbreak.

Causing bouts of diarrhea, abdominal cramps, nausea, vomiting and low-grade fevers the illness can cause pain so severe that you curl up in tears. It is also a hard hitter to your pocket book. The parasite infection has had patients selling out thousands of dollars for treatment.

Most parasites are killed when chlorine is added to swimming pools. Not this hardy parasite. Because of that it’s hard to kill and easy to cause serious outbreaks. Found in human and animal feces it transmitted easily to others when in water supplies.

The parasite is a single cell 20 times smaller than the width of a human hair. When it is in the water it lives in a small egg that is resistant to cold, moist conditions. It’s a perfect mix for swimming pools. It also can live for a long time, continuing to reinfect people until it is finally eliminated.

Not only have outbreaks taken place in pools and lakes. In 1993 an outbreak in Milwaukee, Wisconsin occurred when it got in the drinking water supply. 400,000 people got sick and about 100 of those died. Most of those who succumbed to the parasite had underlying illnesses such as AIDS and cancer.

There are no medical treatments to cure the parasite. It generally will disappear on its own in two weeks to a month. Until it’s out of the body treatment of diarrhea may be needed if it becomes severe.


One response to “Parasite That Causes Major Outbreaks Is Immune To Chlorine

  • batguano101

    Swimming pools and boil water advisories-

    Atlanta, Georgia

    There was a storm last week and a boil water advisory was announced.

    What does a “Boil Water Advisory” mean?
    What about Swimming pools?

    Here is what the Center for Disease Control has to say about it.

    Cryptosporidiosis (Cryptosporidium Infection)
    Cryptosporidiosis is a diarrheal disease caused by microscopic parasites of the genus Cryptosporidium. Both the disease and the parasite are commonly known as “Crypto.”
    Many species of Cryptosporidium exist that infect humans and a wide range of animals. 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 resistant to chlorine disinfection.
    While this parasite can be transmitted in several different ways, water is a common method of transmission and Cryptosporidium is one of the most frequent causes of waterborne disease (drinking water and recreational water) among humans in the United States.

    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.
    By swallowing recreational water contaminated with Crypto. Recreational water can be contaminated with sewage or feces from humans or animals.
    By swallowing water or beverages contaminated by stool from infected humans or animals.
    By eating uncooked food contaminated with Crypto. All fruits and vegetables you plan to eat raw should be thoroughly washed with uncontaminated water.
    By 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 cow or calf.

    Hikers who drink from unfiltered,
    untreated water sources are at higher
    risk for Crypto infection.
    People with greater exposure to contaminated materials are more at risk for infection, such as:
    Children who attend day care centers, including diaper-aged children
    Child care 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.


    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. Other symptoms include:
    Stomach cramps or pain
    Weight loss
    Some people with Crypto will have no symptoms at all.

    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 spp. at the species level.
    Causal Agent:
    Many species of Cryptosporidium exist that infect humans and a wide range of animals. Although Cryptosporidium parvum and Cryptosporidium hominis (formerly known as C. parvum anthroponotic genotype or genotype 1) are the most prevalent species causing disease in humans, infections by C. felis, C. meleagridis, C. canis, and C. muris have also been reported.


    Hydration applies to all diarrhea.
    Most healthy people recover with only oral intake of fluids.

    nitazoxanide (Alinia®, Romark Laboratories)

    Adult dosage
    500 mg BID x 3 days
    Pediatric dosage
    1-3 years: 100 mg BID x 3 days
    4-11 years: 200 mg BID x 3 days

    Practice good hygiene.
    1.Wash hands thoroughly and frequently with soap and water.
    a.Wash hands after using the toilet and before handling or eating food (especially for persons with diarrhea).
    b.Wash hands after every diaper change, especially if you work with diaper-aged children, even if you are wearing gloves.
    2.Protect others by not swimming if you are experiencing diarrhea (this is essential for children in diapers). Swimming is not recommended for at least 2 weeks after diarrhea stops.
    Avoid water that might be contaminated.
    1.Do not swallow recreational water
    2.Do not drink untreated water from shallow wells, lakes, rivers, springs, ponds, and streams.
    3.Do not drink untreated tap water during community-wide outbreaks of disease caused by contaminated drinking water.
    4.Do not drink tap water that has not been boiled or ice that has not been made from boiled water when the public health department advises boiling water (boil water advisory).
    5.Do not use or consume untreated ice or drinking water when traveling in countries where the water supply might be unsafe.

    If you are unable to avoid using or drinking water that might be contaminated, then you can treat the water for Cryptosporidium by doing one of the following:
    Heat the water to a rolling boil for at least 1 minute.
    Use a filter that has an absolute pore size of 1 micron or smaller, or one that has been NSF rated for “cyst removal.”

    It is important to inform local, state, and federal health authorities about cases of cryptosporidiosis so that appropriate public health responses can be taken to help control the spread of this disease.
    Related Outbreak Management Links
    For more information about public health responses and managing cryptosporidiosis outbreaks, see the recommendations at the following sites:
    Boil Water Advisories
    Day Care Facilities – Control Measures for Outbreaks
    Recreational Water Outbreak Response Toolkit
    Drinking Water Outbreak Response Toolkit
    Foodborne Disease Surveillance and Outbreak Investigation Toolkit
    Cryptosporidium and Water: A Public Health Handbook (PDF – 1.1 MB, 151 pages)
    Note: The “Issuing and Rescinding a Boil Water Advisory” portion of the Handbook is superseded by the Boil Water Advisories that appear on this site. Please note: Some of these publications are available for download only as *.pdf files. These files require Adobe Acrobat Reader in order to be viewed. Please review the information on downloading and using Acrobat Reader software.
    Page last modified: April 16, 2008
    Page last reviewed: April 16, 2008
    Content Source: Division of Parasitic Diseases (DPD)
    National Center for Zoonotic, Vector-Borne, and Enteric Diseases (ZVED)

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