Having been a wildlife rehabber since 2008, I've seen some pretty gross things, but the thing that gets me every...single...time...are warbles. SO gross! These are the larvae of a botfly. There are many species of botflies all over the world. In the U.S they generally start to lay their eggs around mid-summer to the first frost. This fuzzy-looking fly will land on a host, be it a wild or domestic animal OR a human, and lay its eggs. When the eggs hatch on the skin of the host, the larvae enter into the host by way of its mouth or nose, and get under the skin where they grow. When I got this little squirrel in October 2016, it looked like it had an abscess but..when I put water in the opening, I could see little air bubbles coming up...the larvae trying to breath through the water. Ah ha! I knew right away what was going on. I took the squirrel to my vet and she used forceps to remove the warble. They have little hooks that they hang onto the animal with and it's vital that you get the entire thing; if it breaks apart the section left in the animal can cause infection. Once the warble was removed, the hole closed up within days and the squirrel was fine. These parasites generally do not permanently affect their hosts; they grow up, climb up out of the hole and drop onto the ground where they continue to grow. Only in cases where there are excessive larvae will the host be harmed. These little buggers are one of my least favorite things to deal with as a rehabber!