I've had about five or six migraines, three of which I suspect were
brought on by eating contaminated pork or fish.

Each time, the migraine would be preceeded by a visual aura. The aura
basically looked like a long but narrow spider web stretching
horizontally across my field of vision. It glowed a bright white color
and pulsed and flickered as if some kind of electrical current were
flowing through it. The strands of the web seemed thick and flat. The
aura remained in one part of my field of vision; I believe it was the
lower-right side. So that no matter where in the room I looked, the
aura would remain there. It disappeared before the actual pain began.