Dear Holly,
How about a recluse spider bite?  On humans it looks like a circle size red
spot, and in the center it looks like a scab, it starts out small and the
circle enlargens, the ventom eats away at the flesh, and gets really nasty,
eventually it reaches the bone.
 
I am so scared of them, I have worked with a Woman who was bitten on her
wrist while sleeping in her water bed.  Within 24 hours she was rushed to
the hospital and they did surgery to remove the infected area, and there was
a woman there who was being treated for 7 recluse bites on her legs :( And
my sister, while crawling under the crawlspace of her house in Oklahoma, was
bitten, unknown to her, and by the 3rd day, couldn't sit or lay down, my
mother went over to inspect her tailbone, and found the nastiest circle of
red, the size of half dollar, and what looked like a scab in the center, my
sister went to the doctor and started treatment.  She is fine now.
 
Ask your Vet about it, I would rather sleep with a snake, which I am afraid
of, than get bit by a brown recluse spider!!!!!!!!!  And since ferrets crawl
into weird places, they probably come into contact with them more often.
Good luck, and if your vet can't help you FIND SOMEONE who can determine the
cause of the suspicious looking sore, and take immediate action.
 
Marti
[Posted in FML issue 1776]