BLACKOUT open thread!

What is going on with toxoplasmosis in humans is that the parasite is trying to modify behaviour as though it were still in the normal small-rodent host, and getting things a little bit wrong. That it even gets a lot of things to work just shows how much brain chemistry is conserved in mammalian physiology; this isn't always the case. With parasites like loa-loa what you get is infected with a nematode parasite which isn't a human or even a primate parasite and once in humans gets a bit lost. The larval nematodes know that they have to migrate, and do just that (feeding along the way) but the biochemical markers that say "You have now arrived in the right spot to complete development" don't exist, so they just wander and wander.

To be honest, the notion of zombie-like behaviour being caused by a parasite has occurred to several authors before; "Night on Mispec Moor" by Larry Niven, for instance, but a parasite that acts somewhat like the Cordyceps fungi do on ants would be interesting to see.

There is also a school of thought expounded by myself and a friend, Mr Jon Downes, that quite a few of the supposed lake monsters of northern Europe and America can be explained as giant eels. European eels are strange creatures; they spawn in the Sargasso sea, then migrate to Europe across the Atlantic and enter river systems here, and spend years growing to a size at which they can spawn again. When this comes, a biochemical switch in their heads gets flipped (and can be flipped back to the "grow up" setting in a few cases) and they develop sexual characteristics, and migrate back to the Sargasso to breed and die.

It is a common characteristic of fish parasites, though, that they castrate their hosts. This in the case of eels (which I do not think are the principal host of this parasite, merely occasional victims) would prevent migration leaving the eel to live on, growing bigger, and bigger, and bigger. Captive eels have been recorded as surviving over thirty years; who knows how big a wild-living one could get?

BTW, I have a PhD in parasitology.