Pathogen Census Study

Tuberculosis, other potential human pathogens in Charleston waterways, CofC study finds

By Shamira McCray, Post and Courier, May 28, 2022 

A DNA project conducted last fall found a number of potential human pathogens in Charleston’s waterways, with some of the top being tuberculosis, staph, cholera and E. coli.

When bacteria levels are high, there’s an elevated risk of coming into contact with one of these pathogens. Charleston Waterkeeper reports the bacteria levels online each week from May to October. 

Charleston Waterkeeper collected water samples in October 2021 from 20 different locations in the Charleston area. College of Charleston biology professor Michael Janech then used the samples to determine the different viruses, bacterium and other microorganisms present in the water.

Andrew Wunderley, executive director of Charleston Waterkeeper, said 12,000 different bacteria and fungal species were found in the samples, including some genes that are antibiotic resistant. More than 5,000 of the species were potential human pathogens, or ones that could cause disease in the right environment.

Biologists have known for some time that after storms and floods, bacteria levels tend to skyrocket in Charleston waterways. 

“But this new data shows that it’s not just high bacterial levels,” Wunderley said. “We can confirm that a lot of these nasty pathogens are also present.

Samples were taken from a number of areas around the Charleston Harbor including the Cooper River, Shem Creek, James Island Creek and the Ashley River.

Janech and other researchers wanted to build a database of the findings. And he said he wasn’t surprised by what showed up in the samples.

“Many of these human pathogens exist either in reservoir hosts, such as animals, or they exist in soil and water and they’re always there, but they’re not necessarily infectious,” Janech said. 

It is likely that the species entered the water through human and animal waste. Floodwater could be a potential pathway, as could untreated or poorly treated sewage discharges, septic tanks or congregations of wildlife. 

Getting rid of septic tanks in the immediate Charleston Harbor watershed is critical to prevent this type of pollution, Wunderley said.

Floodwater and heavy rains can overwhelm the drain fields and pull the waste out with it. 

Investing deeply in sewer infrastructure is another important measure to prevent accidental spills or sewer overflows.

“Generally speaking, our sewer plants operate pretty well except for when we’re having a big flood or like a heavy downpour during a hurricane or something like that,” Wunderley said. “It can really experience problems during those events.”

While is is possible that the tuberculosis found in Charleston Waterkeeper’s samples can cause disease in humans, it’s difficult to predict when it would happen, Janech said.

For example, a potential human pathogen can exist in seawater and not cause disease there. But it could possibly produce a disease if it gets into freshwater. Janech said these species are sensitive to salts and different environmental conditions.

Findings from this study were taken from samples collected on a single morning in October 2021. Janech said that leaves researchers wondering what else might be in the water the rest of the year, especially on rainy days or during warmer temperatures.

But the current data could be helpful for public health workers interested in better understanding the environment or people who are immunocompromised and want to decide whether to go swimming in Charleston’s waterways.