Left: Electron microscope image of Naegleria fowleri in its cyst stage. Center: Electron microscope image of Naegleria fowleri in its ameboid trophozoite stage. Right: Electron microscope image of Naegleria fowleri in its flagellated stage.
Left: Electron microscope image of Naegleria fowleri in its cyst stage. Center: Electron microscope image of Naegleria fowleri in its ameboid trophozoite stage. Right: Electron microscope image of Naegleria fowleri in its flagellated stage. Photo credit: Centers for Disease Control and Prevention.

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By Rose Hoban

Whitewater facilities at a Charlotte water park where a teen acquired a fatal amoebic infection could be closed for long time, according to health authorities in Mecklenburg County.

Mecklenburg County Health Dept. Medical Director Stephen Keener appraises county commissioners about the status of the Whitewater Center. Screenshot of Mecklenburg BOCC webcast

At a county board of commissioners meeting last week, Mecklenburg Health Department Medical Director Stephen Keener told commissioners that the popular whitewater channel at the U.S. National Whitewater Center would be closed while it got a thorough cleaning and disinfecting, and for some time beyond.

“We don’t have a timetable for it because it really is a unique situation,” Keener told county commissioners.

“Yes, but two years, four years or six months?” asked Ella Scarborough (At-Large).

“We don’t want to rush into any decisions,” interjected Cardra Burns, the county’s assistant health director. “So we want to take as long as possible to be sure that we can rectify it.”

The US Whitewater Center in a Google Earth image. The loops on the right and left are each closed and all the water has been drained from the upper pond as the Center cleans.

The unique nature of the facility — an unregulated body of recreational water that’s not really a pool and not really a river — has gotten many folks concerned about how to reduce numbers of the organism that killed Ohio teen Lauren Seitz, 18.

While deaths from Naegleria fowleri are rare, experts in water treatment and engineering say there are ways to keep it from infecting the water at places such as the Whitewater Center.

And they say what the Whitewater Center was doing was “inadequate.”

A persistent organism

Part of the problem with reducing the risk for N. fowleri infection is that it’s everywhere in the environment, in soil and mud.

The cysts — sort of like eggs — of this single-cell organism can survive becoming hot or cold, becoming desiccated, and even being exposed to chlorine, according to Nick Ashbolt, a public health and water engineering professor from the University of Alberta in Canada. N. fowleri thrives in warm water, he said.

Left: Electron microscope image of Naegleria fowleri in its cyst stage. Center: Electron microscope image of Naegleria fowleri in its ameboid trophozoite stage. Right: Electron microscope image of Naegleria fowleri in its flagellated stage. Photo credit: Centers for Disease Control and Prevention.

“In Australia where I grew up, in the mid-’70s we had cases, and identified the organism in treated drinking water carried overland in pipes, where temperatures were able to get up to 28-30 degrees Celsius (82-91 degrees Fahrenheit),” Ashbolt said. “It can even grow if it’s in clean, low-nutrient drinking water with no chlorine residual.”

At those higher temperatures, chlorine evaporates, leaving few agents behind to kill persistent organisms such as N. fowleri cysts and amoebas. When it’s hot, chlorine has to be continually added to the water in order to keep residual levels consistent.

[pullquote_right]According to tests performed by the Centers for Disease Control and Prevention, chlorine at the center’s water came in at below-detectable levels,[/pullquote_right]“What’s being now suggested in the warmer parts of the U.S. is to keep (water) at about 0.5 milligrams per liter of chlorine residual, which is thought to be sufficient to suppress growth,” Ashbolt said.

He said people can detect chlorine in water at about 0.2 milligrams per liter, while swimming pools operate at about 1.0 milligrams per liter.

“At that level, a swimming pool should be quite safe,” he said.

But according to tests performed by the Centers for Disease Control and Prevention, chlorine at the center’s water came in at below-detectable levels: 0.15 milligrams per liter total.

“These results indicate that water did not contain sufficient free chlorine residual for disinfection,” according to Jennifer Cope, a medical epidemiologist and infectious disease specialist from the CDC’s Waterborne Disease Prevention Branch.

See box below: How much is enough?

Turbidity reduces chlorine’s effect

The water at the Whitewater Center had a lot of organics and particulates from the river and from runoff. The channel was only about 4 feet deep, allowing for it to get warm, and the water was continually churning.

“Water like that when you add chlorine to it, the chlorine reacts with all that debris and is automatically consumed, so it’s no longer present to inactivate a pathogen like Naegleria fowleri,” Cope said during a press conference on June 30. Cope told reporters that chlorine, along with ultraviolet light filtration of the type used at the Whitewater Center, can kill the amoeba. However, the system at the center was “inadequate,” she said.

“For reference, turbidity levels in properly chlorinated recreational water venues should not exceed 0.5 NTU (Nephelometric Turbidity Units),” Cope wrote in a subsequent email. But the turbidity measured at the USWWC was 6.7 NTU, more than 13 times that level.

Pumps fill the upper pool from the lower pool at the US Whitewater Center. Currently, the upper pool is closed as the facility is being cleaned and all the water is being stored in the lower basin. Photo credit: HowardMorland, Wikimedia Commons

“Because these measurements were taken from a single spot in the Whitewater system, it’s impossible to say the results are reflective of the state of the water throughout the entire system,” Cope added, noting that turbidity in the nearby Catawba River was 4.1 NTU.

“What is happening at the Whitewater Center is the water isn’t being treated properly,” Travis Heggie, from Bowling Green University in Ohio, wrote in an email. “The water may be slightly treated with chlorine, but not in the right amounts … so we end up with water with a lot of soil and organic content in it and boom — you have a victim.”

Heggie, who researches travel and wilderness medicine, cited an incident at a water park in Arkansas where there were two cases of meningitis related to N. fowleri: “The owners were adding chlorine to the water. They just weren’t adding enough.”

State lawmakers have shown themselves willing to force the Whitewater Center to do more treatment.

Late in the legislative session, which wrapped up July 1, Rep. William Brawley (R-Matthews) tacked an amendment onto a different water bill to pull the Whitewater Center into the state’s regulatory regimen.

The bill passed the House, but didn’t make it through the Senate before lawmakers left Raleigh for the year.

Warmer waters, more cases?

Traditionally, N. fowleri and related infections in the U.S. have been confined to Southern states, where waters warm up in the summer, allowing the amoeba to proliferate. But in recent years, researchers have tracked cases of N. fowleri derived from waters as far north as Minnesota.

Pakistani researchers publishing in 2014 found a rise in the number of deaths in less-developed countries from primary amoebic meningoencephalitis (PAM), the form of meningitis caused by N. fowleri. As noted, cases are usually related to people swimming and jumping into warm rivers, lakes and pools.

“Rising temperatures in recent years due to global warming, together with poor infrastructure of wastewater management and sanitation as well as drug resistance, will cause a further rise in the number of deaths due to infectious diseases in general and PAM in particular,” the researchers concluded.

Warmer waters are a worry for a number of researchers who look into N. fowleri, including Heggie and UNC-Chapel Hill environmental engineer and water researcher Mark Sobsey.

“What we know is that there is this trend towards an average increase in temperature and water temperature and there are more extreme temperature events,” Sobsey said. He pointed to incidents of gastrointestinal problems from people eating shellfish from far northern estuaries, where bacterial loads were traditionally low.

All the researchers said there’s not enough data yet to draw a bright line between the increased numbers of microorganisms and climate change, but Heggie was willing to say climate change was “probably” to blame.

“We think that PAM infections might continue to be seen farther north than we have historically seen,” Cope agreed.

Ashbolt is concerned enough that he’s dispatched a postdoctoral student to test waters near him.

“We have a lot of shallow fresh-water bodies in Alberta and we have temperatures that get up to these levels,” he said. “Luckily we have not found any… yet.”

 

Rose Hoban

Rose Hoban is the founder and editor of NC Health News, as well as being the state government reporter. Hoban has been a registered nurse since 1992, but transitioned to journalism after earning degrees...