Deep in forests around the world a strange fungus is lurking. It doesn’t grow on trees, or from the ground like so many other fungi that we are familiar with. Instead, this fungus infects an unfortunate insect, turning it into a mindless zombie and control of its body until the fungus matures, erupting from the dying insect.
Think this sounds like a plot line from the X-Files? It’s not.
For some unfortunate insects this actually happens; enter the Cordyceps fungus.
So far on this site I’ve tried to address microbiology topics from all areas of the field; from the standards in bacteriology and virology to some more exotic parasites and fungal infections. When you look at the range of infections that people can acquire you see many bacteria, viruses, and parasites. However, invasive fungal infections, especially those that occur in healthy immune-competent hosts, are exceedingly rare when you compare mammals to insects, plans, and amphibians. I never gave this much thought until coming across a group of papers that together indicate that something as fundamental as a warm body temperature could protect us from a variety of pathogenic fungi.
Maybe it’s the Halloween spirit and all the zombies I’ve been seeing everywhere, but this week I can’t help but write about two very different kinds of microbes that infect the brain. I’ve already covered a virus that causes encephalitis and meningitis, and many bacteria can cause septic meningitis. However, the two organisms in the news this week that are causing fatal brain infections are neither a virus or bacteria, and much less common. The first is Naegleria fowleri, a warm-water dwelling amoeba; the second is Exserohilum rostratum, a nearly ubiquitous fungus found in the soil and on plants. These organisms normally live in very different environments but both have the unusual ability to infect the brain under very specific circumstances with fatal outcomes.