09.23.13 9:45 AM ET
This Amoeba Eats Your Brain: Naegleria Fowleri Rattles New Orleans
Health officials have disclosed that a 4-year-old boy who died in August was killed by an extremely rare infection of the brain called Naegleria fowleri. The disease is seen a few times each year in the U.S. and is one of the odd infections caused not by bacteria, viruses, fungi, or parasites. Rather, Naegleria is a free-living amoeba—that one-cell organism familiar to junior high school science class students, then quickly forgotten.
In more than 25 years of practicing as an infectious disease specialist, I have never seen a case of Naegleria, a testament to its rarity. But I have frequent worries if not nightmares about it. Naegleria is altogether Aliens-like. Most human infections are contracted by inhaling, ingesting, or inoculating a pathogen. From there it needs to enter the bloodstream to be carried to the brain. But Naegleria enters the brain directly through the nose. There is a secret passageway that allows access to the central nervous system (the brain and spinal cord) through something called the cribriform plate, a small stretch of skull bone punctured by multiple tiny holes that nerve fibers traverse. Some have conjectured that because of this unique anatomic arrangement, the sense of smell more than other senses is “hardwired” to the brain, perhaps giving smell its uniquely evocative power.
These same small holes though create a weak link in the brain’s otherwise thick-boned defense—the amoeba is able to slither through and gain access to the brain. From there, it is a simple matter to quickly overwhelm the local immune defenses, resulting in death in almost all cases. There is no established treatment for the infection though various experimental therapies have been tried, some with some very modest success. The occurrence in humans of a related amoebic infection, called Acanthamoeba, which causes superficial eye infection, has helped researchers develop treatment strategies. Acanthamoeba infections have occurred in contact-lens wearers probably because the solution may, if improperly stored, lack enough antimicrobials to kill off the various bacteria and fungi that may thrive in the rich solution. Though uncomfortable, Acanthamoeba infection is not fatal, and involves only the cornea, the cell layers on the outside of the eyeball. Treatments for Acanthamoeba are now being tried in those with Naegleria.
In addition to being rattled by the tragedy of a young boy dying, this case has locals in the St. Bernard Parish of New Orleans concerned because of how he acquired the infection. Naegleria lives in fresh-water—ponds and rivers. Most cases occur when someone—usually a young boy—goes for a dip in a pond on a hot summer day and somehow enough Naegleria-infested water gets into his nose to set up a lethal infection. Pond and river water, unlike municipal water, is untreated—not filtered, not spiked with chlorine to kill things like Naegleria. So the occurrence of the infection in a person exposed to pond water is, although heart-breaking, somewhat logical.
This 4-year-old however apparently contracted the disease while playing on a Slip ‘n Slide that was connected to treated municipal water. In other words the hose pumping water into the Slip ‘n Side was contaminated with the amoeba. During the slippery frolicking, water possibly kicked up into a spray that the little boy snorted high into his nostrils. The specifics are important—if indeed this is how he caught the infection, his will be perhaps the only case in the U.S. whose infection occurred after contact with filtered and treated domestic water. Further supporting the theory is the recent disclosure that chlorine levels in the St. Bernard water system were indeed low and that Naegleria had been detected in the municipal water.
The Centers for Disease Control and Prevention (CDC) and local health authorities have gone to great lengths to point out the rarity of the condition and the fact that drinking Naegleria-contaminated water is safe. They are right—it does not cause stomach or intestinal problems, only the devastating brain infection. Plus the St. Bernard water has been flushed with plenty of chlorine, making it almost certainly completely clear of Naegleria or any other dangerous pathogen.
Yet distrust of authorities often worsens after a tragedy—after all, where were they when the opportunity to prevent the infection presented itself? But maintaining adequate levels of chlorine on hot days can be a real challenge—it evaporates quickly on hot summer days and must be frequently replenished. As more facts are known, the tragedy likely will be explained by a failure of government, yet is in fact a screaming endorsement of its necessary-if-annoying presence in everyday life to preserve public health and safety. People have to pay taxes to pay the guy to put the chlorine in the water; if they don’t, we are all in danger.