Naegleria Risk May Rise When Water Supplies are Underchlorinated

A new outbreak of the brain-attacking amoeba Naegleria fowleri claimed the lives of ten victims in Karachi, Pakistan this year, according to an October 10 CNN report. Tests of the city’s water supply found either no chlorine or insufficient chlorine levels in 22 percent (198 of 900) of samples taken around Karachi. Officials linked the outbreak to inhaling Naegleria-contaminated water during the Muslim nostril cleansing ritual known as Waddu. A Karachi Water Board official vowed to increase the chlorine level of the city water supply, which serves over 15 million consumers. The tragedy underscores the importance of maintaining a protective level of disinfectant in public drinking water supplies.

Naegleria: Rare but Dead

Last December, we reported on the deaths of two Louisiana residents who had succumbed to Naegleria. Both victims had used “Neti pots” filled with warm tap water to flush their sinuses. Subsequent investigations (see study) showed no detected amoeba in either the municipal water treatment plant or distribution systems serving these residents. Naegleria was found, however, colonizing the household hot water systems of these residences. It is not known how Naegleria was introduced into household plumbing. Remediation of these systems included raising hot tap water temperatures.

Until recently, the rare Naegleria infection was associated mainly with swimming in freshwater lakes and rivers, particularly during periods of high water temperature and low water levels. Improperly chlorinated swimming pool water can also host Naegleria, highlighting another reason to maintain adequate pool water chemistry, with free chlorine in the range of 1 to 3 parts per million and pH between 7.2 and 7.8.

The Centers for Disease Control & Prevention (see online resource) urges Neti pot users to use distilled, sterile or previously boiled water (least expensive option) to prepare the irrigation solution. People cannot be infected with Naegleria by drinking contaminated water, but if Naegleria-contaminated water is inhaled, the parasite can migrate from the human nose to the brain, causing amoebic meningoencephalitis and almost certain death.

The Value of a Chlorine Residual

The World Health Organization resource, “Measuring chlorine levels in water supplies” explains that chlorine not only kills microorganisms effectively at the point of disinfection but also supplies a residual level of disinfectant downstream from the point of treatment. If enough chlorine is added to water, some will remain in the water after all possible organisms have been destroyed, leaving a low level of “free chlorine” residual, a kind of public health “bodyguard” for water.

As water flows from the treatment plant to the tap, residual chlorine remains available to destroy new contaminants encountered in the distribution system. By monitoring the residual chlorine level at points along the distribution system, the physical integrity of the distribution system can be gaged. If, for example, a chlorine residual level disappears between Monitoring Point A and Monitoring Point B, it may be inferred that there is a potential source of contamination in the distribution system between these two points that should be addressed.

It is very good that Karachi officials will be more attentive to appropriate chlorine levels in the city’s water supply. Meanwhile, however, and in view of the Louisiana deaths from Naegleria, forewarned is forearmed: Muslims participating in Waddu and Neti pot users everywhere should exercise precaution and heed the warning to use distilled, sterile or previously boiled water for nasal irrigation.

Chris Wiant, M.P.H., Ph.D., is president and CEO of the Caring for Colorado Foundation. He is also chair of the Water Quality & Health Council.