Giardia in Drinking Water

Giardia in Drinking Water

Question #1: What is Giardia?

It is a one celled, protozoan parasite that is microscopic in size. You could fit 10,000 cysts on the period at the end of this sentence they are so small. It is usually transmitted in cyst form. The cyst has an egg-shell type of covering that protects the cyst and makes it able to survive outside the the human or animal body for long periods of time. It is so protected that it can survive chlorine and so small that it can get through even well run community water treatment systems. It causes an intestinal illness that is called giardiasis or more popularly "beaver fever".

Question #2: How does Giardia get into our drinking water?

This parasite lives in the intestines of humans and animals, both wild and domestic animals. In the intestines it multiplies and in cyst form passes out of the body in the stool of humans and animals. One bowel movement can release millions of cysts into the environment. From there they can be passed in numerous ways to other humans. One way is through water. Rain or snow can wash it into lakes, streams and rivers or they can seep into ground water and wells. Hence, runoff water from animal farms or sewage from towns and cities dumped into rivers are often sources of contamination.

The contamination is passed not only through drinking water but also through any contact with human or animal waste that contains cysts. For example, a person who doesn't wash their hands after going to the toilet can pass cysts on with a hand shake. Day care workers who change diapers frequently can pass them on or infect themselves. Places of public swimming can be a source of infection if one accidentally drinks some of the water. Sometimes it is hard to know the exact source of contamination.

Question #3: How can giardia affect my health?

It can take only a few cysts to infect a person. The incubation period for the disease of giardiasis or "beaver fever" is 6 to 16 days and the symptoms can last up to a month or more. There are different degrees of intensity and different variations of the symptoms. A bout of giardiasis can include intense diarrhea, stomach cramps, gas, vomiting, headaches, fever and chills.

The disease resolves usually without treatment within a month. Antibiotics are sometimes used or other drugs that treat the symptoms. See your doctor for treatment. In the case of people with low resistance, like HIV/AIDS or cancer patients or people with transplants, this parasite can be life-threatening. For most people otherwise it's a miserably uncomfortable disease that you just have to endure. Hence, it's worth all the precautions necessary to avoid it.

Question #4: How big a problem is Giardia in our drinking water?

To give you a general idea of how widespread the problem is, let me quote the "Fact Sheet on Giardiasis" put out by the Division of Parasitic Diseases (DPD):

During the past 2 decades, giardia infection has been recognized as one of the most common causes of waterborne diseases (found in both drinking and recreational water) in humans in the United States. Giardia is found worldwide and within every region of the United States.

It is very difficult to know the exact extent of the number of people infected because often it is not reported and even when reported takes time to find in a laboratory. It is believed that far more people are infected annually than we realize.

Question #5: How can I know if Giardia is in my drinking water?

The cyst is so small that it is difficult to find even under a microscope, particularly in water where only a relatively few cysts can be the cause of infection. However, the Environmental Protection Agency has set the standard, namely that it should be totally disinfected (killed) or removed (by filer). Water treatment systems are required to report the presence of this parasite in tap water.

If you get your tap water from a public water system, they are required by law to send you annually a Consumer Confidence Report (CCR). If you don't have a copy you can get one from your city hall. Look to see if there are "cysts" in your water. They cite the "Level Found" and the "MCL" (Maximum Contaminant Level). The standard set by the EPA is "zero". Any water which contains some is not safe. The water company is required to state in the CCR that they are present. They are also required to inform the public through newspapers and television of their presence in the water. Usually, they will tell you to boil your water for drinking or food preparation.

Question #6: How would I go about removing Giardia from my drinking water?

When there is an outbreak of giardiasis in an area due to drinking water, the public is usually advised to boil their drinking water until told otherwise. One should boil the water for a full minute to kill the parasite. This, however, is a short-term solution.

The best long-term solution for protecting yourself against this and other parasites is that of filtration. There are two kinds of filters that can remove it from your tap water: Filtration (carbon/charcoal)with a pore size of 1 micron or smaller and Ultraviolet water treatment systems that meet Standard 55A of the NSF.

Which ever one you choose should not only claim to destroy or remove cysts but also have third party certification of that claim. For example, check the NSF International which is the best source of filter certification.

For further information on the best filters in the categories of Filtration and Ultraviolet go to "Best Water Filters". Or for a broader discussion of the multiple considerations you need to keep in mind in selecting a filter go to "How to Choose a Water Filter".

For more information about this and other toxic contaminants, go to "Giardia in Drinking Water".

SUMMARY TABLE