Protozoan Drinking Water Contaminants
Protozoa represent another type of drinking water contamination. These creatures live in soil, water, and in the intestines of humans and other mammals and contaminate water when it comes into contact with sewage and animal waste. Protozoa are neither bacteria nor viruses and have fairly complex life cycles compared to other waterborne pathogens. Although the cycles of different protozoa vary somewhat, the basic cycle consists of these stages:
Stage One: The protozoan oocysts (eggs) enter the body via food or water that has come in contact with feces.
Stage Two: Upon ingestion, the cysts break open from contact with stomach acids.
Stage Three: The organisms move into the intestines and begin to reproduce.
Stage Four: The new eggs leave the body in fecal material and wait for the opportunity to begin the process again.
This is a very simplified example of the protozoan life cycle, but even a small sample of feces from an infected host may contain millions of protozoan cysts.
The Main Protozoan Culprits
These three protozoans are the most common threats to drinking water safety as they are somewhat resistant to normal levels of the chlorine used to control waterborne pathogens.
Cryptosporidium parvum is responsible for cryptosporidiosis which causes symptoms such as fever, headache, vomiting, nausea, cramps, and diarrhea. Usually, the symptoms subside after one week and rarely last longer than two weeks. For people with compromised immune systems such as infants, the elderly, and AIDS patients, cryptosporidiosis can be deadly. The most notable outbreak of this disease occurred in Milwaukee, Wisconsin in 1993. It killed more than 100 people and sickened over 400,000 more in what has become one of the most infamous cases of waterborne illness in recent memory.
Giardia lamblia causes giardiasis with symptoms such as diarrhea, cramps, nausea, general intestinal distress, and weight loss. The symptoms begin within the first week of exposure, rarely last longer than two weeks, and seldom result in anything more serious than intestinal cramps and frequent trips to the bathroom. The most recent significant outbreak of giardiasis occurred in a suburban Boston children�s swimming pool in 2003. Thirty primary cases of infection resulted in more than 105 cases of secondary infection, and new cases were found over four months later.
Naegleria fowleri causes amebic meningoencephalitis which inflames the tissues of the brain and can lead to death in three to seven days if not diagnosed and treated quickly. The initial symptoms are headache, fever, nausea, vomiting, and stiffness in the neck. As the brain tissues are destroyed, people experience dizziness, seizures, hallucinations, and loss of balance. In 2002, two five year-old boys near Phoenix, Arizona died when they drank water from a municipal water supply that was contaminated with Naegleria fowleri. Studies suggest that this pathogen becomes most active in underground water in warmer climates.
Because protozoa tend to be more resistant to standard chemical filtration like chlorination, a multi-step approach seems to be the best way to filter these critters out of our drinking water. A whole house filtration system consisting of activated carbon, ultraviolet light, reverse-osmosis, and other filtration methods seems to be the most effective way to eliminate these pathogens.
If you�re camping or looking for a quick method for removing protozoans from smaller amounts of drinking water, bringing water to a boil for a couple of minutes is a very reliable way to kill them and prevent contamination. If you get your drinking water from a private well and are concerned about protozoan contamination in your water, you can call your county water commission for a list of reputable laboratories nearby that can perform a comprehensive test of contaminants for a reasonable fee.