My cat recently had a upper respiratory infection and ran a high fever
for over a week. That was about 2 weeks ago that he came down with the
illness, not long after adopting him from a local shelter. Since then
the fever appears to have stopped as he is now less lethargic, willing
to play, gets excited for food and follows me everywhere. Whereas
before he slept most of the day, wasn't interested in playing and I had
to syringe or spoon feed him. His nasal and eye discharge cleared up
about a week ago.

At his worst I had to syringe feed him Hill's A/D (at least 1/2 can per
day). I have since switched back to regular cat food (Whiska's pacakged
food in gravy). He eats close to 2 packages per day without any force
feeding. Yet according to his body weight (10 lbs 3 ounces) he should
be eating about 4 1/2 pacakges a day (based on Whiska's
recommendation). He is a 4 year old male maine coon that has tested
negative for FIV and FELV. His water intake is also fairly low. I
assume as I am feeding him foods with a lot of moisture he just doesn't
require a lot of water.

A typical adult male maine coon should weigh 14-17 lbs from what I have
read, so he is a little underweight. I am concerned he will slowly
waste away at his current nutrional intake level. He doesn't appear to
be weak, but I can't see him gaining or maintaining his current weight
if he continues to eat only that much.

My vet has recommended putting him on appetite stimulants. For his
current food intake is this maybe a little overboard? I was thinking of
trying to feed him higher calorie kitten food and maybe some nutrical.

I realize he is in a recovery stage, as a cat with a URI may take a few
weeks to get back to "normal". Should I be terribly concerned for his
health at his current food intake? Or is it something that needs to be
addressed but not deathly urgent?

Thanks
Trevor