He has actually followed up on this in another column, answering the question Morbid Curiousity thought he was asking, and showing evidence that roundworms ditch an unconscious or stressed host like rats fleeing a sinking ship.
BTW, read that column only if you aren’t squeamish. If you have a vivid imagination, the things described there are borderline nightmare fuel.
Anyway, I mention this only because it can be hard to find the tie-in between columns. I found the second column only because it was the top hit for googling “roundworm anesthesia”.
I have seen the parasites leaving after anesthesia phenomenon firsthand. One of my dogs had knee surgery and when I brought him home, after he had the call of duty, his poo had several hookworms wriggling in it. After almost barfing I poured some bleach on them and shoveled it into the doggie poo composter. We had recently treated him for hookworms, but I don’t think the dose was high enough. Needless to say we retreated him for them.
I didn’t look at the reference – that’s why I didn’t want to become a doctor – but hey, you mean you’ve never seen the worms wriggling in your OWN poo? What a first world life you’ve led