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Identification of Naegleria fowleri in domestic water sources by nested PCR
Francine Marciano-Cabral1, Rebecca MacLean, Alex Mensah
1Department of Microbiology and Immunology, Virginia Commonwealth University/Medical College of Virginia Campus, Richmond, Virginia 23298-0678, USA. fmcabral@hsc.vcu.edu
Abstract:
The free-living amoeboflagellate Naegleria fowleri is the causative agent of primary amoebic meningoencephalitis (PAM), a rapidly fatal disease of the central nervous system. In the United States, the disease is generally acquired while swimming and diving in freshwater lakes and ponds. In addition to swimming, exposure to N. fowleri and the associated disease can occur by total submersion in bathwater or small backyard wading pools. In the present study, swipe samples and residual pipe water from homes in Arizona were examined for N. fowleri by nested PCR due to the death of two previously healthy children from PAM. Since neither child had a history of swimming in a freshwater lake or pond prior to the onset of disease symptoms, the domestic water supply was the suspected source of infection. Of 19 samples collected from bathroom and kitchen pipes and sink traps, 17 samples were positive for N. fowleri by PCR. A sample from a Micro-Wynd II filter was obtained by passing water from bathtubs through the filter. Organisms attached to the filter also tested positive by PCR. The two samples that tested negative for N. fowleri were one that was obtained from a kitchen sink trap and a swipe sample from the garbage disposal of one home.
Insights
Naegleria fowleri, the cause of fatal primary amoebic meningoencephalitis (PAM), was found in domestic tap water. This finding suggests household plumbing may be a source of infection, even without swimming exposure.
Area of Science:
- Environmental microbiology
- Infectious diseases
- Public health
Background:
- Naegleria fowleri causes primary amoebic meningoencephalitis (PAM), a severe and often fatal central nervous system infection.
- PAM is typically acquired through recreational water activities like swimming and diving in freshwater.
- Recent cases in children lacking typical exposure histories prompted investigation into alternative infection sources.
Purpose of the Study:
- To investigate the domestic water supply as a potential source of Naegleria fowleri infection.
- To determine the prevalence of N. fowleri in household plumbing systems in Arizona.
Main Methods:
- Nested PCR was used to detect N. fowleri DNA in water samples.
- Samples included swipe samples and residual water from pipes, sink traps, and filters from homes.
- Testing was prompted by two pediatric PAM cases with no history of swimming.
Main Results:
- Naegleria fowleri was detected in 17 out of 19 samples collected from household plumbing.
- Positive samples included bathroom and kitchen pipes and sink traps.
- N. fowleri was also identified on a filter used for bathtub water, confirming its presence in the water system.
Conclusions:
- Household plumbing systems, including pipes and filters, can harbor Naegleria fowleri.
- Domestic water supply represents a significant, previously underestimated, route for N. fowleri exposure and PAM infection.
- This highlights the need for increased awareness and potential interventions targeting domestic water sources.
