Well since no-one has the faintest guess I'll answer my own question. I haven't seen the feathers on my feather duster for a long time -weeks. But I always noticed it was still attached to some CC I used to have. It wasn't mushy either. Last night I was very close to throwing it out, but noticed just the very tips of it coming out - first time in a month I bet. I think its still alive.
I've asked about this in an earlier thread - weeks ago, and no one answered that one either. Are you telling me nobody has had this happen, or nobody knows anything about sick feather dusters>????????