Update on my sick Moose

I just left the Vets. Moose continues to run a fever but it is slowly coming down. They have him on an IV and oral antibiotic. He is eatting now & had 2 BMs today (both clear of any foreign body, no blood, and no diarrhea.) The abdominal x-ray today showed no peritonitis, his incisions look good, and he does not seem to be hurting when they feel his abdomen. He is however still very lethargic & seems to be in pain with the rectal temp checks. I asked the Vet what he thought might be going on. He asked if we noticed any ticks (I have not but we do live near the woods and I don't check his body all over for them.) He asked about salmon posioning (we havn't had salmon for 3+ weeks and I don't think he got any out of the garbage when we did.) He says he keeps going back to his surgery and the possibility of an abcess but Moose would have abdominal tenderness and pain if that was the case. We just don't know what in the heck is going on. I am hopeful that we can bring Moose home in a couple of days. I am so worried about him and miss him. He did seem to be moving a bit better today, I actually saw his tail wiggle when I came in. He doesn't look like he is in severe pain with any kind of movement like he did on Monday, but he is still moving very slowly and seems to have little to no energy.
If anyone has any idea what it could possibly be or advice on what we should be doing, I would love to hear from you.
Thanks for all the well wishes for Moose.
Shell