OK, well, you need to have someone find the nest, and get rid of it; and you will have to make sure there are no other places other than the vent where they can get in, and close those up.
I am here as well; I have merely been keeping a low profile. Wishing you well with your diagnosis @Charlet. Knowing for certain what it is that ails you is the first step toward effective management of it.
Breaking news: historians believe that they've uncovered a cache of pencils that once belonged to William Shakespeare. A spokesperson said, "They're so badly chewed on the ends, we can't tell if they're 2B or not 2B."
"Napoleon attacked by rabbits" so I had to go google search it. "The story of Napoleon being "defeated" by rabbits during a hunt in 1807 is a humorous anecdote, but it's not a confirmed historical fact, though it is mentioned in General Thiébault's memoirs. "