The cat probably has worms & should be wormed. You can get wormer from the veterinary. I had a cat dumped off last year that was skin & bones & very freightened of everything. She is still not trusting of us or other cats but is fat & sassy. Another thing if the cat has bitten someone that wound should be washed throughly. I was bitten by a cat once & ended up with blood poisoning & ended up in the ER receiving a penicllian shot & pills. It took a long time for the puncture wound to heal too. Cats have a lot of bad bacteria in their mouths that can harm humans. I do have a milk formulal given to me by our veterinary with lots of protein in it that may help the cat. Here goes 1/2 Cup Evaporated Milk, 1 egg Yolk, & 1 tsp. of Light Karo Syrup, you can add liquid vitamins to this formula also. I got some liquid cat vitamins at Wal Mart & added that also. I mix this formula up to feed motherless kittens. Also Bless You for taking this cat in. Be patient & work slowly around it.