If you have other mounts, I'd suggest inspecting them and keeping an eye on them. Typically if one mount has "bugs' then others most likely do too. Setting off a "bug bomb" with your mounts in an enclosed room will eventually kill them, but you will need to do it more than once as the eggs are rarely killed. Doing multiple treatments spaced out a week or so should catch them in one of their other stages after hatching. It's actually an on-going thing as dermistids are everywhere and can enter your house at about any time. Just a matter of time before they find something nice to chew on.