‘Brain eating’ perhaps sounds rather dramatic, but the Naegleria fowleri amoeba, which is usually found in warm, freshwater lakes and rivers, has an unpleasant effect in human beings – if it enters the nose it can migrate to the brain via a nerve, and cause a rare form of meningitis called primary amoebic meningoencephalitis. Researchers used PCR (polymerase chain reaction) to trace two deaths in Louisiana back to contaminated water used in nasal irrigation, with the results published in Clinical Infectious Diseases.

Neti pot

Source: Aikhan

Primary amoebic meningoencephalitis is almost always fatal, with death within one to 12 days of infection. Symptoms include headache, fever, nausea and vomiting, stiff neck, fits and hallucinations. There have been incidents and outbreaks seen in Czechoslovakia, New Zealand, the UK, the USA, Pakistan and Vietnam.

Infection with this amoeba usually happens when swimming, but neither of the people who had died in Louisiana had recently been swimming in open waters. However, both people (who were unrelated) had used tap water and neti pots for nasal irrigation. The researchers tested water samples, tap swab samples and neti pots from both households, and found a variety of amoebae. Using PCR, they identified some of these as Naegleria fowleri in water samples in both homes, including in the water heater, tap, bath, sink or shower.

According to Jonathan Yoder, coordinator of waterborne diseases and outbreak surveillance at Centers for Disease Control and Prevention (CDC) said, these were “not found in the treatment plants or distribution systems of the municipal water systems servicing the patients’ homes.” The research could not pinpoint how the amoeba got into the plumbing of the patients’ houses, but once they were there, the organisms were able to colonize the hot water systems. This is the first time that contaminated tap water has been linked to Naegleria fowleri infections in the USA.

People often use salt to decontaminate the water before nasal irrigation, but the team found that these did not have any effect on reducing the number of Naegleria fowleri amoeba over four hours, let alone the few minutes that generally happens in practice.

Deaths from N. fowleri infection, which remain very rare, “are tragic for the families of those infected,” Yoder said. He and his team suggest that only boiled water or water labelled as sterile should be used for nasal irrigation, because simply adding salt will not kill the amoeba. Doctors in areas that have seen Naegleria fowleri outbreaks should also be aware of this as a possible cause for meningitis, especially as climate change could increase the organism’s range, and as it has been found in warm spa waters as well.

Suzanne Elvidge is a freelance science, biopharma, business and health writer with more than 20 years of experience. She is editor of Genome Engineering, a blog that monitors the latest developments in genome engineering and that aims to educate (and sometimes to entertain!) and has written for a range of online and print publications including FierceBiomarkers, FierceDrugDelivery, European Life Science, the Journal of Life Sciences (now the Burrill Report), In Vivo, Life Science Leader, Nature Biotechnology, PR Week and Start-Up. She specialises in writing on pharmaceuticals, biotechnology, healthcare, science, lifestyle and green living, but can write on any topic given enough tea and chocolate biscuits. She lives just beyond the neck end of nowhere in the Peak District with her second-hand bookseller husband and two second-hand cats.