Naegleria fowleri, often called the “brain-eating amoeba,” is a microscopic organism that causes a severe brain infection. Public concern frequently arises regarding its presence in tap water, but infections are exceedingly rare. This article clarifies facts about Naegleria fowleri and its connection to water systems, helping to understand the organism and minimize risks.
Understanding Naegleria Fowleri
Naegleria fowleri is a single-celled organism classified as a free-living amoeba. It thrives in warm freshwater environments, such as lakes, rivers, ponds, and hot springs. This amoeba is also commonly found in soil. It is a thermophilic organism, meaning it prefers warm temperatures, growing best between 25°C and 46°C (77°F and 115°F).
The amoeba exists in three main life stages: the cyst, the trophozoite, and the flagellate. The trophozoite is the infectious form, which can transform into a temporary flagellate stage. The cyst stage allows the amoeba to survive unfavorable conditions. Only the trophozoite stage is infectious to humans.
Presence in Water Systems
Properly treated public tap water is safe and free of Naegleria fowleri due to disinfection processes like chlorination. Water utilities maintain disinfectant levels to control harmful microorganisms throughout the distribution system. Naegleria fowleri cannot survive in water that is adequately chlorinated.
However, there are rare circumstances where the amoeba could be detected in tap water systems. This might occur in cases of inadequate water treatment, insufficient disinfectant, or breaches in water infrastructure. For instance, it has been found in poorly maintained swimming pools, water heaters, untreated private well water, or water stored in tanks at high temperatures. While uncommon in municipal systems, these instances highlight the importance of proper water management.
How Infection Occurs
Infection with Naegleria fowleri occurs exclusively when water containing the amoeba is forced up the nose. This can happen during activities like swimming, diving, or playing in warm freshwater, where water might enter the nasal passages under pressure. Another route of infection can be through the use of unboiled tap water for nasal rinsing, such as with neti pots.
Once the amoeba enters the nose, it travels along the olfactory nerve to the brain, causing a severe and rapidly progressing brain infection called Primary Amebic Meningoencephalitis (PAM). Swallowing water contaminated with Naegleria fowleri does not cause infection, as the amoeba is destroyed by stomach acid. This means there is no risk from drinking tap water.
Minimizing Risk
To reduce the risk of Naegleria fowleri infection, especially during activities involving nasal contact with water, several precautions can be taken. When performing nasal irrigation using devices like neti pots, use distilled, sterile, or previously boiled and cooled tap water. Boiling tap water for at least one minute effectively kills potential pathogens, including this amoeba.
For those engaging in recreational activities in warm freshwater bodies like lakes or rivers, limiting the amount of water going up the nose can be helpful. This includes holding the nose shut, wearing nose clips, or keeping the head above water. Avoiding stirring up sediment in shallow, warm freshwater areas is also recommended, as the amoeba is more likely to reside there. Proper chlorination in swimming pools and spas also prevents the amoeba’s survival.
Recognizing Infection
The infection caused by Naegleria fowleri leads to Primary Amebic Meningoencephalitis (PAM), a rapidly progressing condition. Initial symptoms, such as headache, fever, nausea, and vomiting, typically appear about five days after exposure, though this can range from one to twelve days.
As the disease advances, more severe symptoms may develop, such as a stiff neck, confusion, lack of attention, loss of balance, seizures, and hallucinations. PAM progresses quickly, often leading to a coma and death within one to eighteen days after symptoms begin. If these symptoms occur after exposure to warm freshwater or after nasal irrigation with potentially contaminated water, immediate medical attention is important.