Concern over ameba-infested tap water deaths

By Helen Albert, Senior medwireNews Reporter

People with sinusitis who regularly treat their condition using nasal irrigation should be aware of a potential contamination risk associated with using inadequately filtered tap water, say US researchers.

They report two deaths occurring following nasal irrigation using disinfected tap water that was contaminated with the Naegleria fowleri ameba.

Infection with N. fowleri is rare, with 32 reported cases in the USA between 2002 and 2011, but is 97% fatal. This is due to destruction of brain tissue by the organism during primary amebic meningoencephalitis (PAM) following its migration up the nasal passage. Occasionally patients respond to being treated with very high doses of the antifungal drug amphotericin B, but treatment is usually given too late to be effective and even if effective has severe side effects, such as nephrotoxicity.

The two cases described by Jonathan Yoder (Centers for Disease Control and Prevention, Atlanta, Georgia) and colleagues in Clinical and Infectious Diseases are the first reported cases of PAM occurring after exposure to contaminated tap water. N. fowleri infection usually occurs after swimming in warm, contaminated open water such as lakes, ponds, or rivers.

The two individuals who died, a 28-year-old man and a 51-year-old woman, both from Louisiana, were admitted to hospital and died within 5 days from PAM. They had both been using neti pots, a sinus irrigation device, to treat their sinusitis. On testing, the water systems of both households were found to be contaminated with the ameba.

Worryingly, the reconstituted salt packets provided with the neti pots for disinfection purposes were ineffective at reducing the amount of N. fowleri present in water over a 4-hour period.

However, Yoder emphasizes that other simple methods of filtration and disinfection can ensure the safety of water used for nasal irrigation purposes.

When asked about the best ways to avoid using contaminated water for nasal irrigation, Yoder told MedWire News that people should use water that has been "previously boiled for 1 minute (at elevations above 6,500 feet, boil for 3 minutes) and left to cool; filtered, using a filter with an absolute pore size of 1 micron or smaller; or purchased with a label specifying that it contains distilled or sterile water."

He also suggested that people should "rinse the irrigation device after each use with water that has been previously boiled, filtered, distilled, or sterilized, then wipe the inside dry or leave the device open to air dry completely."

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