Hi, Megan!  While I don't have any ideas on what might be wrong with your
fuzzy, I do have ideas on fattening him back up!  Basically, these are
things I did with my Scooter, when he was recovering from helicobacter.
(The helicobacter had made him VERY skinny!)
 
Alicia from Ferretwise and my vet helped me to figure out a formula to
fatten him back up.  Some of the ingredients were:
 
- Brewer's yeast
- Ground ferret food (I used TF, and kitten food)
- Molasses
- Lecithin
- Papaya enzyme
- Cooked egg yolks
- Rice water (water which has had rice boiled in it for a bit)
- Chromium
- Nutrical
 
(There might have been some other ingredients, which I am forgetting).
Basically, you make it up in a blender, and feed it to the fuzzy using
feeding syringes - no needles).  It will keep in your fridge for a couple
of days, and then you let individual servings warm to room temperature
before serving.  Hope this helps!
 
- Ela
 
P.S.  Scooter loved it!
 
P.P.S.  Might want to run it by your vet. before starting on it; we sort of
"custom-tailored" this design to Scooter's condition - other conditions
might require different combinations of ingredients ...
[Posted in FML issue 2450]