I’m sure you don’t need to ask how the microbe Naegleria fowleri earned its nickname the “brain-eating amoeba.” Yep, it makes its way into your noggin and starts to gobble down brain tissue using sucker-like structures called amoebostomes, which unfortunately make the hungry organism look like a terrifying human face. But it turns out that scientists may have been a little hasty to solely blame this amoeba’s taste for brain on the horrific and fatal disease which ensues.
According to new research, a major player in the infection is actually our own body’s response to its presence, which causes significant destruction to neurons. But that doesn’t mean N. fowleri is off the hook; it worsens the situation and causes irreversible brain damage, which may even continue after the patient dies. Although infections are currently almost always deadly, with a case fatality rate of 97%, the researchers behind this new study are hopeful that this knowledge could be put to good use and lead to improved treatments, which may boost survival chances. The work has been published in Acta Tropica.
Naegleria fowleri is a tiny free-living amoeba found across the globe in bodies of warm fresh water, like hot springs or lakes. It normally spends its days chomping on bacteria, but in the unfortunate circumstance of a human getting contaminated water forced up their nose, for example during water sports, it can go on to cause an extremely nasty infection, to say the least.
After shooting up the nose, it invades the lining of the nasal cavity and makes its way along the olfactory nerve – the cell responsible for relaying information about smell to the brain—until it reaches the olfactory bulbs. Once here, it starts to munch on brain tissue using its specialized feeding cups, which ultimately results in the patient’s loss of smell and taste. It then continues on a path of destruction, releasing damaging toxins and enzymes but also triggering an intense reaction from the immune system. Although this exists to help fight infections, amongst other things, it actually worsens the situation.
While we already knew that the presence of this microbe in the brain triggered severe swelling due to inflammatory molecules flooding to the area en masse, this new literature analysis suggests that this reaction also disrupts the fragile shield which protects our brain, called the blood brain barrier. Not only does this leave our brain susceptible to other unwelcome visitors, but this excessive bombardment by members of the immune system seems to inadvertently further destroy brain tissue. Eventually, with the blood brain barrier compromised, the inflammation gets to severe that the brainstem gets crushed, a fatal end to the infection, New Scientist reports.
To examine this further, study author Abdul Mannan Baig, from the Aga Khan University in Karachi, and others designed an experiment to compare how well brain tissue survives infection with and without the immune system. They grew brain cells in a dish and infected them with N. fowleri in the presence or absence of relevant members of the immune system, which revealed survival increased by about 8 hours when immune cells weren’t there.
Although further research is warranted, this could indicate that suppressing the immune system in infected individuals before going after the amoeba with drugs may improve the chances of survival. However, as pointed out by the Centers for Disease Control & Prevention’s Jennifer Cope, testing this out will be tricky given that cases are so uncommon. But that could change, thanks to the gradual warming our planet is witnessing, which could encourage the organism to crop up in more and more places as they heat up.
