It sounds like he is just really depressed.  Ferrets will grieve themselves
to death.  They don't eat and sometimes they don't drink.
 
Have you thought about getting him a playmate.  He is lonely.  I am a
definite believer that every ferret needs a companion.  When I got my first
little girl, my friend kept insisting that she needed a companion.  I really
didn't think so, but I gave in and the next day went out and bought another
ferret.  It made so much difference in Faith.  Hope was just what Faith
needed.
 
Please try that.  From what little I know, nothing was strikingly wrong with
the test.  Depression can cause our bodies to get sick.  I bet you can save
him by getting a new ferret, maybe a shelter one.
 
Phyllis and the four Wigglies, Faith, Hope, Charrity and Charlie Brown
[Posted in FML issue 2346]