Digitally Detecting Waterborne Illnesses

By Marguerite Huber

Toxoplasma gondii oocysts

Toxoplasma gondii oocysts

The smaller something is, the harder it is to find. Just try finding a needle in a haystack, or low concentrations of pathogens such as Toxoplasma gondii (T. gondii) and Cryptosporidium in drinking water. These two human pathogens are the leading causes of protozoan waterborne illnesses (toxoplasmosis and cryptosporidiosis), so they are something the drinking water industries are working hard to monitor.

To understand exposure risks associated with T. gondii and Cryptosporidium, sensitive and accurate detection and clinical diagnostic tools must be in place. The lack of such tools make environmental monitoring for these parasites challenging.

One of the biggest issues with monitoring human pathogens is that if it is environmentally transmitted (such as through drinking water), its concentrations can be very low, making it difficult to detect with current water monitoring practices.

EPA researchers have recognized that detection is the biggest challenge. They are working to help bring current methods–which rely on a technique known as polymerase chain reaction (PCR) that amplifies genetic material (DNA) for further analysis—into the digital age. They have designed software to assess the performance and detection limits of digital PCR (dPCR) to accurately quantify low concentration levels of T. gondii and Cryptosporidium.

Dr. Eric Villegas, a scientist working on the project explains, “Digital PCR can perform up to a million reactions in the same amount of time that standard techniques take, improving how we model the detection of waterborne pathogens.”

This capability of dPCR offers a whole new set of opportunities, including greater statistical power to detect if the pathogen is present and, if so, to determine its concentration. “The software that we developed assesses the quality of the data collected and determines the concentration of pathogens with high precision and accuracy,” researcher Dr. Scott Keely, explains. Ultimately, this approach will provide additional sensitivity for quick and accurate diagnosis of parasite infections.

Overall, this research will detect pathogens better and faster than existing methods, which will allow policymakers, drinking water utilities, and managers to scrutinize available data, analyze it with confidence, and learn what type of data to collect in the future. Most importantly, it will help minimize any health risk related to drinking and recreational water quality by providing decision-makers with methods and tools that decrease the amount of time to reach decisions regarding the management of water bodies or other sources of drinking water where these pathogens are of potential concern.

About the Author: Marguerite Huber is a Student Contractor with EPA’s Science Communications Team.

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