Vulture feathers are every bit as sanitary as any other molted bird feather. Vultures take advantage of the UV germ killing of natural sunlight to bake the creepie-crawlies off their heads and feathers. And just to add to the general information out there, large hawk/vulture/eagle feathers are no better than wild turkey feathers. In some cases the web of the feather is actually less stiff than that of turkey feathers. I've handled enough of them at various raptor centers to get a feel for them. BUT you really don't want even a single unauthorized feather to show up in your possession because once you have an arrest on your record you are under suspicion for life. Ain't worth it. Not even with my Federal Raptor Permits is it worth it!
Many of the parrot breeders that you might go to for these macaw feathers are shipping all their molted feathers to an organization that distributes them between a number of Native American tribes. These feathers often have greater religious significance than those of raptors. Trade routes into Mexico, Central America, and even South America provided these feathers and even the live birds to these Southwestern peoples.