Search the forum boards under 'Disease Immunity' and you'll get an old thread from 2005. From which I will excerpt the following from 'Gold Katana' Nov. 2005:
"Although the worms are destroyed when in a victim's body by casting Remove Disease and Remove Curse, they are neither a disease nor a curse. Per Dungeon 126, they are "a Fine vermin," per Dragon 336 "they are a strange symbiotic form of vermin that subsists upon the decaying flesh of the spawn." Also, per Dragon 336, "Once the worm reaches the brain, ... it begins to consume..." I propose Remove Disease and Curse are applicable per gaming rules because there is no "Remove Vermin" spell. A paladin would not be immune to the worms."
By the same rules the Periapt of Health should not work.
At the end of the day you are the final authority of your game. Since there are many times characters encounter the worms in later adventures, this ruling will effect those games also.
Here's a further post from James Jacobs in the same thread:
"Paladins aren't immune to Kyuss worms. Disease in D&D is a specific game mechanic; you suffer ability damage once per day after an incubation period until the disease is removed or you make your 2 Fortitude saves in a row to recover. Kyuss worms, while they are destroyed by remove disease function in a completely different manner than an actual disease.
Now if you want to say paladins are immune to Kyuss worms in your campaign, that's cool. But keep in mind that once you start to blur things like this, there will be ramifications. If you make a paladin immune to Kyuss worms, then why aren't they also immune to green slime, brown and yellow mold, chaos beast bites, and slaadi egg implantation?"
In my game, I allowed the periapt of health to prevent and cure the worm infestations. On the other hand, I also ruled paladins could become infected by them like anyone else.
To be honest though now that my AOW campaign is completed, I can look back and say I would rather have treated the worms more like an actual infestation and not a disease. That would have allowed me to invent something special to get rid of them that the PCs had to track down before it's too late, and once they find this rare magic concoction, keeping in supply and making it (probably a use for Alchemy) would have been more fun than simply spending a handful of gold on an amulet and being forever immune to them thereafter. It really made things easier on the PCs, but easy on the PCs was not really as much fun in the long run, IMHO.
In my game, I allowed the periapt of health to prevent and cure the worm infestations. On the other hand, I also ruled paladins could become infected by them like anyone else.
To be honest though now that my AOW campaign is completed, I can look back and say I would rather have treated the worms more like an actual infestation and not a disease. That would have allowed me to invent something special to get rid of them that the PCs had to track down before it's too late, and once they find this rare magic concoction, keeping in supply and making it (probably a use for Alchemy) would have been more fun than simply spending a handful of gold on an amulet and being forever immune to them thereafter. It really made things easier on the PCs, but easy on the PCs was not really as much fun in the long run, IMHO.
That's a fairly good point. I'll definitely keep that in mind when i run this in the near future. Thanks for the insight.