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Cryptosporidium in Water: CDC Guidelines on How to Protect


AIDS Treatment News Issue #227, July 21, 1995

Cryptosporidiosis is caused by a microscopic parasite, Cryptosporidium parvum, and may cause severe diarrhea. Persons with normal immunity get cryptosporidiosis, but recover without treatment within several weeks. In persons with immune deficiency, however, the disease can be life- threatening; there are treatments which sometimes reduce the symptoms, but no known treatment is effective in getting rid of the parasite in severely immunosuppressed persons.

Cryptosporidium is spread by contaminated water, as well as by contact with infected persons or animals. The risk from water came to national attention in 1993, when over 400,000 people got cryptosporidiosis from the Milwaukee water supply, despite purification according to Federal standards. Cryptosporidium can be found in most U.S. rivers, lakes, and streams. While a well-operated and equipped municipal water purification system can remove most of it in drinking water, these systems cannot guarantee its complete removal.

On June 16, 1995, the U.S. Centers for Disease Control and Prevention (CDC) issued guidance regarding Cryptosporidium and water supplies.(1) This 19-page document includes two and a half pages concerning immunocompromised persons. Points include: * "All immunocompromised persons should be educated and counseled about the ways that Cryptosporidium can be transmitted (e.g., sexual practices involving fecal exposure, contact with infected adults or with infected children who wear diapers, contact with infected animals, drinking or eating contaminated water or food, and exposure to contaminated recreational water." * "All persons, especially immunocompromised persons, should avoid drinking water directly from lakes or rivers. Because water can be ingested unintentionally, immunocompromised persons should be advised that swimming in lakes, rivers, or public swimming pools can also place them at increased risk for infection." * "During waterborne outbreaks or other situations in which a community boil-water advisory is issued, immunocompromised persons should boil water for 1 minute to eliminate the risk for acquiring cryptosporidiosis. Using submicron, personal- use filters (i.e., home or office types of water filters) or high-quality bottled water also can reduce the risk for transmission. However, boiling water is the most certain method of killing Cryptosporidium oocysts [the infectious stage of the parasite's life cycle]." * "Only microstraining filters capable of removing particles less than or equal to 1 micrometer in size should be used by immunocompromised persons and other persons who choose to use a personal-use filter (i.e., home or office water filters) to reduce the risk for transmission of Cryptosporidium.

Filters in this category that provide the greatest certainty of Cryptosporidium removal include those that produce water by reverse osmosis, those labeled according to filter manufacturing industry standards as "Absolute" 1 micrometer filters, and those labeled as meeting American National Standards Institute (ANSI)/NSF (formerly the National Sanitary Foundation) International Standard #53 for "Cyst Removal." [Footnote: NSF International certifies water filters according to the ANSI/NSF International Standard #53: Drinking Water Treatment Units -- Health Effects.

To obtain information regarding the current status of any water filter, contact NSF International, 3475 Plymouth Road, P.O. Box 130140, Ann Arbor, Michigan 48113-0140. Telephone 800/673- 8010.] The "Nominal" 1 micrometer filter rating is not standardized, and many filters in this category might not reliably remove oocysts.

Filters that only employ ultraviolet light, activated carbon, or pentiodide-impregnated resins are not effective against Cryptosporidium. Not all filters advertised as effective against Giardia are effective against Cryptosporidium.

Because bacterial overgrowth on filters can be a additional health risk and oocysts are likely to concentrate on the outside of filter cartridges, persons should carefully follow the manufacturer's instructions for filter replacement and use.

Immunocompromised patients should either have someone else change the used cartridges or use disposable gloves if they themselves change the cartridges." * In a longer discussion on bottled water, the CDC recommendations noted, "Many brands of bottled water adequately reduce the risk for cryptosporidiosis and, thus, provide a reasonable alternative to boiling tap water. However, labeling of bottled water is not standardized with regard to the manufacturing practices used to test for and remove or kill Cryptosporidium oocysts...." The recommendation discusses risks from different sources of bottled water. But whatever the source, "Bottlers who treat water before bottling by distillation or reverse osmosis filtration, regardless of the source (e.g. well, spring, and municipal tap water), insure removal of oocysts if they are present. Similarly, water that has been passaged through an "Absolute" 1 micrometer or smaller filter or through a filter labeled as meeting ANSI/NSF International Standard #53 for "Cyst Removal" before bottling will provide almost the same level of oocyst removal..." The document suggests, "Persons who use bottled water as an alternative to tap water that has been boiled must carefully research and choose their supplier." Unfortunately no list of safe waters is provided; there is a voluntary effort by the bottling industry to improve labeling, but it will probably take about a year to put into place.

"Current data are inadequate to make a general recommendation that immunocompromised persons in the United States boil or avoid drinking tap water in nonoutbreak settings. However, immunocompromised persons should be advised that the risk for waterborne transmission is possible and that they can choose to reduce their risk for waterborne cryptosporidiosis by using precautions similar to those recommended during outbreaks. Immunocompromised persons should consult their health-care provider before making such a decision." Whatever precaution one uses, it is important to use them for all water consumed. "Preliminary data from outbreak investigations indicate that persons who did not consistently use bottled water or filters were as likely to become ill as those who did not use such products." Who Is at Risk? We asked Dr. Dennis D. Juranek at the CDC who should be most concerned about water safety -- is there any agreement that people below a certain CD4 (T-helper) count should take the special precautions? He said that had been discussed in the workshop which developed the guidelines. But while clearly those with low CD4 counts -- under 200, or especially under 100 -- are at greater risk for getting serious illness immediately from Cryptosporidium, it may be possible that persons earlier in HIV disease could recover from cryptosporidiosis but not clear the parasite completely, allowing it to cause serious illness later. Until more is known about this possibility, the guidelines are targeted at everyone with HIV.

Dr. Juranek explained that the CDC did not have enough information to issue a "recommendation" that immunocompromised persons not use tap water everywhere in the U.S., and issued "guidance" instead. "Basically the reason is that we do not know what the magnitude of risk is for acquiring Cryptosporidium from drinking water during non- outbreak periods, and we do not know what percent of Cryptosporidium infections are acquired from drinking water vs. the other modes of transmission. We have some preliminary data indicating that sexual practices that result in fecal exposure may be among the highest risk activities; remember that not all Cryptosporidium infections in HIV/AIDS patients are symptomatic...

"Also, the risk of waterborne infection is likely to vary considerably from city to city depending on the quality of a city's source of drinking water and water treatment processes. For example, in some cities water comes from high- quality well water (no evidence of fecal contamination ever). Persons in such towns would not be at risk for waterborne cryptosporidiosis. Other towns have a lot of human sewage discharge upstream (sewage treatment does not kill all Cryptosporidium), and even brief treatment interruptions at a water treatment plant using such water may place AIDS patients at high risk.

"We are also concerned about the life-style changes that may be necessary for a person to make sure that all his/her drinking water is boiled/filtered/bottled. This basically means that one has to carry water to work and for recreation, e.g. no fountain drinks (syrup mixed with carbonated tap water) at fast food establishments, restaurants, movie theaters, etc. At home people would have to remember to use boiled, etc., water to prepare juices or other cold beverages normally reconstituted with tap water.

"So the question each person must ask him/herself is, 'Is this worth it? Is the waterborne risk in my town great enough for me to do this?' We would not answer these questions for immunosuppressed persons who live a variety of life styles in cities whose water quality is also highly variable." Bottled Water Quality We also asked Dr. Juranek about choice of bottled water. He said that there is no adequate technology today for testing either bottled or city water to see if it is safe. Water treated by distillation or reverse osmosis should be OK -- but if the label says it is treated by ultraviolet light, ozone, or microfiltration, that may not be enough to remove or kill the parasite.

Also, the source of the water is important. Water from a well which is tested twice a week for years and has shown no fecal contamination ever is probably free of the parasite. Some of the major bottlers in Europe and the U.S. take pride in their wells; they own the land around the site and take care of it to maintain their water quality.

Another View AIDS TREATMENT NEWS spoke with Donald P. Kotler, M.D., a leading AIDS gastroenterologist. He is not happy that the CDC refuses to make a recommendation on drinking water and leaves it to each patient to make his or her own decision.

Dr. Kotler recommends taking the special precautions with drinking water if one's CD4 count is below 200. This is based on a study which found that above 190, people usually recovered from cryptosporidiosis spontaneously, while below 190 they seldom did. Dr. Kotler said there is little evidence that Cryptosporidium not being completely cleared is a common problem, although of course there are asymptomatic cases. And if a person is exposed to the parasite in the course of their usual lifestyle, they have probably been exposed to it already.


Copyright © 1995 -AIDS Treatment News, Publisher. All rights reserved to AIDS Treatment News (ATN), Email AIDS Treatment News .

Information in this article was accurate in July 21, 1995. The state of the art may have changed since the publication date. This material is designed to support, not replace, the relationship that exists between you and your doctor. Always discuss treatment options with a doctor who specializes in treating HIV.