I would like to thank everyone who posted-I had no idea that such a good discussion would result from my original post. I did some work in a laboratory in Baltimore in the 1960's where anthrax cultures existed for vaccine development purposes, and there were EXTREME precautions in the building; negative air flow to each lab, which was filtered through acid before being discharged into the air outside the building. Anthrax is an extremely dangerous disease and untreated, and has a very high mortality rate, especially the pulmonary form. So, I will post pictures of the dangerously attractive NOS horsehair brush in question later this weekend, but not use it until I can have it gas or gamma sterilized. The bleach and boiling suggestions would likely loosen the bristles and damage the wood finish, so I will take a pass on those. Thanks again, all!