Its hard when feral cats are unwell because they just want to run away and hide. We had a cat called baby who was feral, she disappeared and we were desperately looking for her for a couple of days. We eventually found her, she had a paralysis tick and went inside one of our rabbits tunnels, she died there and we were devestated. If we would have seen her symptoms and known what was wrong, we would have taken her straight to the vet.