If your cat / dog is in need of weight gain there are a few options available through a vet and without. I have been working at a vet Clinic as a technician for 6 years if that gives you any confidence in what I am suggesting.
For the cats that do like to eat wet food ask your vet about adding...
Ask your vet about using capstar on your cat if it is indeed fleas it will kill them within 30 minutes and it's a very tiny pill given as(if) needed daily so no licking off chemicals.
