Giardia and Cryptosporidium

Giardia lamblia and Cryptosporidium parvum are protozoan parasites, infecting the digestive tract of man and other warm blooded animals. It has been demonstrated that semi-aquatic mammals can serve as a zoonotic host, transmitting the disease to humans who consume contaminated water. Domestic mammals (particularly ruminants) can serve as an infective host of Cryptosporidium, and, as in Giardia, the animal can contaminate a drinking water supply. Research has also shown that both Giardia and Cryptosporidium are highly resistant to chlorine, a commonly used water disinfectant. Due to the small size of Giardia cysts and Cryptosporidium oocysts (8 to 12 microns and 4 to 5 microns, respectively), both are difficult to remove through filtration.

It is currently believed that approximately 7% of the diarrhea cases in the United States are caused by Cryptosporidium. This figure may be misleading, as causes of diarrhea are seldom tested for by physicians. Cryptosporidiosis can be fatal to immuno-compromised patients. The current infectious dose (ID50) in healthy people is approximately 150 oocysts. The ID50 for immuno-compromised people is believed to be approximately 35 to 50 oocysts.

The Environmental Protection Agency's proposed Information Collection Rule will amend the Safe Drinking Water Act to require microparticulate analysis (MPA) testing for all surface water systems serving more than 100,000 people. MPA tests use the immuno-fluorescence assay method to determine whether or not Giardia and Cryptosporidium cysts are present in the drinking water supply. Systems serving populations greater than 100,000 will be required to perform monthly MPA and viral testing for a period of 18 months.

The purpose of this policy is to address outbreaks of both Cryptosporidium and Giardia, and to further define state policy on responding to detection of these parasites in finished water supplies. This policy will also address when a Boil Water Order should be imposed, and when a Boil Water Order may be rescinded.

When the State Epidemiologist (or their designee) deems an outbreak has occurred (or is occurring) they will immediately notify the Drinking Water Program. The Drinking Water Program will then impose a mandatory Boil Water Order on the water system. This Boil Water Order may be rescinded only by The Drinking Water Program or the State Epidemiologist. Boil Water notices will be posted in accordance with the Drinking Water Program's Policy for Boil Water Orders. The water system shall receive an Acute Violation from the Program.

The System shall undertake Microparticulate Analysis Testing as soon as possible. The Boil Water Order will not be rescinded until the system shows that 3 simultaneous test results indicate an absence of both Giardia and Cryptosporidium. If in the judgment of the Drinking Water Program and State Epidemiologist, the system no longer poses a health threat, the Drinking Water program may lift the Boil Water Order. The Drinking Water Program and/or the State Epidemiologist may require further testing, if in their judgment, the system poses a significant health threat.

If a system utilizing MPA testing for USEPA compliance finds greater than 5 cysts or 50 oocysts per liter of water, the system may, at the discretion of the State Epidemiologist or Drinking Water Program, be placed on a precautionary Boil Water Order. Care should be exercised by the State, not to place unwarranted Boil Orders. The procedure for rescinding the Boil Water Order will be the same as above.

A system finding a result between 1 and 5 cysts and 5 to 49 oocysts, will be required to undergo Public Notification, as outlined for community systems in accordance with Title 40 Code of Federal Regulations Section 141.32. The system should attempt to make a attempt to notify the immuno-compromised population that may be at risk.

Other crypto sites:

U.S. Center for Disease Control
U.S.Food and Drug Administration


Other Giardia sites:

Food and Drug Administration