August 23, 2012 — A rare brain disease previously seen mainly in swimmers is now turning up in some people who use tap water for nasal irrigation.
Jonathan S. Yoder, MSW, MPH, an epidemiologist from the National Center for Emerging and Zoonotic Infectious Diseases at the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, and colleagues studied 2 cases of primary amebic meningoencephalitis (PAM) that occurred in patients who irrigated their sinuses with neti pots and contaminated tap water. The authors report their findings in an article published online August 23 in Clinical Infectious Diseases.
PAM is caused by Naegleria fowleri, a free-living ameba that feeds on bacteria and is often found in natural bodies of warm freshwater. It thrives in warm water (up to 45°C) and most often infects swimmers by traveling up the nose, along the olfactory nerve, through the cribriform plate, and to the brain, killing its victim within about 5 days.
"The 2 cases in Louisiana in 2011 represent the first time disinfected tap water has been implicated in N. fowleri infection. Although N. fowleri are ubiquitous in freshwater aquatic environments, tap water in the United States has previously been implicated only as an uncommon exposure source," the authors write.
The first case was a 28-year-old man from southern Louisiana who became ill in June 2011. He had a 24-hour history of severe occipital headache that radiated down his neck, neck stiffness, back pain, and intermittent vomiting when he arrived at the emergency department and was intubated. On arrival, he was confused, febrile (38.5°C), disoriented, and combative. Despite neurological critical care, he died 2 days later.
The patient had no recent history of exposure to warm freshwater, but did irrigate his sinuses at least once daily with an irrigation device. He used tap water that he treated with a commercially available salt packet.
Investigators took water samples from the municipal water treatment plant and distribution system, and they also took water samples and swabs from the patient's household, sending the samples, along with the irrigation device, to the CDC for additional testing. Water temperatures throughout the home ranged from 103°F to 113°F (39°C - 45°C).
The samples from the municipal water treatment plant and distribution system serving this household contained no amebae, but several types of amebae (Hartmannella, Vannella, and Naegleria sp) were found in some of the samples from the household. Using polymerase chain reaction techniques, CDC scientists found those organisms in water from the home's tankless water heater.
The second case was a 51-year-old woman admitted to the hospital with a 3-day history of altered mental status, nausea, vomiting, poor appetite, listlessness, fatigue, and high fever. On admission she had a temperature of 38.6°C and was lethargic, with neck stiffness and thyromegaly. Tests for specific viral, bacterial, and fungal pathogens as well as the bacterial culture were negative. She died 4 days after admission.
This woman also had no recreational exposure to freshwater in the 2 weeks before she became ill, but similar to the other patient, she used a neti pot to irrigate her sinuses on a regular basis. Her parents did not believe she used distilled, filtered, or previously boiled water in the neti pot.
Water temperatures in her household ranged from 91°F to 115°F (33°C - 46°C). Investigators found N fowleri ameba in water samples from the kitchen faucet, shower, bathtub faucet, and bathroom sink faucet. They found no amebae in the neti pot culture.
Both households were given instructions for remediating the home plumbing.
The researchers also tested the effectiveness of the salt packets to inactivate N fowleri. Four hours after mixing the salt and water, few of the amebae had decreased or degraded, but after 18 hours, more than half had died. The researchers believe that most people use the solution much too soon for the salt to be an effective amebicide.
The authors note that single cases of PAM have also been reported in Minnesota and Kansas.
Patients should be instructed to only use sterile, distilled, filtered (using a filter with an absolute pore size of 1 μm or smaller), or previously boiled water for nasal irrigation, the authors write.
"[I]mproved and systematic environmental sampling of water bodies and systems in the United States is needed to create a baseline for N. fowleri occurrence, followed by systematic monitoring over time to better interpret, understand, and predict potential changes in N. fowleri ecology that could lead to improved prevention activities," the authors write. "In addition, developing efficacious therapies and raising the level of clinical awareness about PAM infections may improve the prognosis for future patients," they conclude.
The authors have disclosed no relevant financial relationships.
Clin Infect Dis. Published online August 23, 2012.
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