Not sure about the poo bit but i have a cat who gets scabs on her back and when i have taken her to vet she has a anti biotic injection that lasts a few days as she wont take tabs but this clears it up.She has a skin allergy to something she used to eat alsorts of different biscuits and meats but not really had the problem since putting her on science plan biscuits.Woud get cat to vets and have him checked out once you get a new carrier .Hope he feels better soon