A few years back a young man in Australia ate a garden slug on a dare and ended up in the hospital with his own immune system chewing through his brain. He survived, barely, and only after months of chaos. The culprit was a parasite you have probably never heard of, a tiny nematode called Angiostrongylus cantonensis, the rat lungworm. The reason that story stuck with me is not the gross-out factor. It is the part nobody talks about. Once that worm gets into your spinal fluid, doctors mostly throw up their hands. There is no proven drug that reliably clears it. People get steroids to calm the swelling and a…