A nod to Ockham's Razor should be given here if indeed groups with chronic parasitosis have less Multiple Sclerosis: "Plurality (of disease in this case) should not be posited without necessity".
I would be quite interested in learning of MS disease rates in those worm infected Mexican children I encountered thirty years ago. I suspect MS prevalence is quite low in such a parasitically challenged population. Ockham would agree they've got enough problems.

