Parasites in Water

In the l980's and l990's they became painfully aware of two problems. One was that there were certain protozoan (one celled) parasites which encased themselves in a shell making them resistant to chlorine. Second, that chlorine itself combined with certain organic chemicals to produce toxic chemicals which were cancer causing. They found that increasing the amount of chlorine used would kill more parasite cysts, though not all; and they realized that there was a good reason for not increasing the use of chlorine in water, namely, it increased the toxic by-products.

Question #1: What are Parasites in Water

There are many kinds of parasites, but here we are talking about the kind that are carried by water. They are one-celled microscopic parasites called protozoan parasites. Now in this category there are a whole list. The ones best known and most widespread in the United States are giardia lamblia and cryptosporidium parvum. Besides these some of the better known are, first, entamoeba histolytica (E. histolytica) causing the disease amebiasis. A severe form of amebiasis is amebic dysentery. It is found more commonly in tropical areas and countries with poor sanitation. Second, Cyclospora cayetanensis produces an intestinal infection called cyclosporiasis. It too is a greater risk to those living in the tropics. In the U.S. it is found most often among travelers and immigrants.

Question #2: How do Parasites get into our drinking water?

These kinds of parasites, protozoan parasites, are usually found in the waste of infected animals and humans. They wreak havoc in the intestines of the person infected and multiply themselves. They,in turn, are passed out through the stool in cyst form. The cyst, with a kind of egg shell protection, is capable of surviving a long time inside or outside of the body. Rain and snow runoff carries them into surface water (streams, rivers, lakes, reservoirs) and seeps them into ground water where they can pollute well water.

One can be infected by this kind of parasite not only through the water one drinks but also through anything that enters the mouth. For example, if a person touches anything contaminated, then touches fruit, that fruit can become the source of infection to whoever eats it.

Question #3: How can Parasites in water affect my health?

Each parasite in water has it's corresponding disease. For example, giardia can give you giardiosis, cyclospora gives cyclosporiasis, etc. They all give gastrointestinal symptoms. Some are very mild and others very severe. The symptoms can include such things as diarrhea, even bloody stools, stomach cramps, gas, nausea, vomiting, chills, headaches and fever.After exposure it can take anywhere from a few days to a few weeks to develop symptoms. These symptoms can last two to four weeks or more.

Because of the nature of the diseases, the victim is in danger of dehydration which in itself can be a major cause of infant mortality in third world countries. In general, for many of these parasitic diseases there is little to be done other than to rehydrate and possibly treat symptoms. There are some antibiotics that can help with some parasites. Check with your doctor on specifics.

Question #4: How big a problem are Parasites in water?

It is hard to say exactly how widespread a problem parasites in water is in our surface and ground water. There have been periodic outbreaks of disease caused by giardia or cryptosporidium in towns and cities in the U.S. and Canada during the past few decades. It's also hard to know if one's infection was due to water contamination or from food contamination.

Dr. Gordon Finch in his scholarly article, "Water Industry Challenge --Waterborne parasites --Part I" summarizes the dimensions of the problem of parasites in the United States as follows:

Given the tenuous nature of the methodology used to count parasites in drinking water, the best that one can conclude is that encysted parasites are ubiquitous (everywhere present) in surface waters...

Question #5: How can I know if Parasites are in my drinking water?

First, understand that it is difficult to test for the presence of parasites in water. They are so small and it takes a special process to make them visible under the microscope. Also it takes only a relatively few cysts to infect a person. For example, for giardia, and infectious dose of cysts is around 50 to 100. But some people have been infected by as few as 10 cysts. You can imagine how hard it is to find a few cysts in a quantity of 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 is cryptosporidium, giardia or cysts in your water. They cite the "Level Found" and the "MCL" (Maximum Contaminant Level). For such parasites, the standard set by the EPA is "zero". Any water which has cysts in it is not safe. The water company is required to state in the CCR that parasite cysts are present. They are also required to inform the public through newspapers and television of the presence of such parasites in the water. Usually, they will tell you to boil your water for drinking or food preparation until informed otherwise.

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

When there is an outbreak of cryptosporidiosis or giardiosis 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 you against protozoan parasites in water is that of filtration. There are two kinds of filters that can remove these parasites 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, the NSF International is the organization best suited for certifying water filters.

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 "Parasites in Water".

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