Waterborne parasites, such as Cryptosporidium and Giardia, pose a threat to public health through drinking water. These microscopic protozoans cause severe gastrointestinal illnesses (cryptosporidiosis and giardiasis). They are particularly concerning because their protective outer shells, called oocysts and cysts, make them highly resistant to standard chlorine disinfection used in many water treatment processes. Testing your water for these pathogens is the necessary first step in safeguarding your household water supply.
When and Why Water Testing is Necessary
The primary reason to test for parasites is relying on a private water source, such as a well, which lacks the regulatory oversight of municipal systems. Owners of private wells should consider annual testing for contamination indicators, with specific parasite testing prompted by certain events. Testing should be initiated if any household member experiences unexplained or prolonged gastrointestinal illness linked to the water supply.
Immediate testing is warranted following a natural disaster, such as a flood, which increases the risk of surface water contamination leaching into the source. A change in the water’s taste, odor, or appearance, or maintenance or failure of a nearby septic system, is also a strong signal to check for parasites. While testing for general bacterial indicators like total coliforms can suggest a pathway for parasites, direct parasite testing offers certainty.
Comparing Home Test Kits and Laboratory Analysis
It is important to recognize the significant difference between at-home kits and professional laboratory analysis for parasite detection. Home test kits, while convenient for detecting high levels of chemicals or general bacteria, are inadequate for reliably identifying protozoan parasites. These kits often lack the precision and sensitivity needed to find the low concentrations of Cryptosporidium oocysts or Giardia cysts typically present in water.
Parasite detection requires sophisticated analytical methods, such as Immunofluorescence Assay (IFA) combined with microscopy or Polymerase Chain Reaction (PCR) techniques. These methods concentrate organisms from large volumes of water and identify their specific structures or genetic material. Therefore, professional laboratory testing, often following U.S. EPA Method 1623, is the only trustworthy route for an accurate parasite assessment.
Steps for Professional Water Sample Submission
The process begins by locating a certified environmental laboratory, ideally one accredited by your state or the U.S. Environmental Protection Agency (EPA) for drinking water analysis. You must request a specialized collection kit, as generic bottles are unsuitable and compromise sample integrity. This kit contains sterile containers, often with a preservative like sodium thiosulfate, and detailed instructions for the required test.
Sample Collection
The sample collection itself must be meticulous to prevent contamination and ensure accurate results. Typically, you will flush the tap for several minutes to clear stagnant water before collecting the sample. The lab will specify the required volume, which is often substantial for parasite testing to ensure a low detection limit, sometimes requiring a large-volume filtration device.
Handling and Sealing
It is necessary to handle the container without touching the inside or the cap’s inner surface. Fill the container to the designated mark, and then securely seal it.
The most time-sensitive step after collection is submission and temperature control. Parasite samples have a short holding time, often requiring submission within 96 hours of collection or sooner. The sample must be immediately chilled and transported on ice or with cold packs, maintained between 2 and 8 degrees Celsius, but never frozen. Following the lab’s chain-of-custody procedures and submitting the required paperwork ensures the results are scientifically sound.
Understanding Your Test Results
A laboratory report indicates the presence or absence of Cryptosporidium oocysts and Giardia cysts, often reporting the concentration detected or a statement of “None Detected.” A positive result, even for a single organism, means the water source is contaminated and poses a health risk. Conversely, a “None Detected” result means no organisms were found above the test’s specific detection limit, but does not guarantee complete absence.
In the event of a positive test result, immediate protective measures are necessary to prevent illness. The first action is to issue a boil water advisory, bringing water to a rolling boil for at least one minute to inactivate the cysts and oocysts. For a long-term solution, you must disinfect the well or source and implement a water treatment system certified to remove parasitic cysts, such as a filtration system meeting NSF/ANSI Standard 53 or 58. These follow-up actions restore the safety of the water supply.