This is supposed to be a throwaway gag, but the joke's totally sinister when you spend 10 seconds unraveling it. First off, Santa Claus and his reindeer are immortal -- that's why we don't change the reindeer names in "Rudolph the Red-Nosed Reindeer" to, like, Roshambo and Cuisinart and Dongle every year.
So precluding the possibility of some sort of peppermint-scented protozoan infection -- which we can't even imagine is a thing, as there are no Christmas carols about such a topic -- Santa Claus upgraded to 4G wireless and promptly slaughtered Vixen and Blitzen and the rest. But why? The reindeer would've happily lived forever, flying around the rafters of a barn, raining endless shit on stable elves for all eternity ... actually, we kind of see where Santa's coming from.