Yes, indeed it is. I think for me, the hardest was with bitchy old Mo. She was an ancient Calico that had lost her home because wifey was allergic/hated cats. She had been with the husband since she was a kitten, found in a graveyard in winter. He was a contact of mine with a recording studio and the bitch wife wanted rid of Mo so much that he had taken Mo to the studio until he could find a new home. Apparently she made friends with some rappers.
We took Mo because she had nowhere else to go. Our cats and dog and her did not really take to each other … we took her to the vet for assessment and discovered that her front claws and not been trimmed for so long that they had grown into her little pads and had become infected.. She had serious liver disease and really matted hair. No wonder she was cross all the time.
Once the claws were cut and she had been given antibiotics for the infection, and mats were brushed out of her fur, she was much better. We dedicated one room to her, which she took full control of. Gandalf refused to let her brush him off and joined her on the window shelf. they had an uneasy relationship for two years until we had to send her over the rainbow bridge.
I always felt horrible that we were unable to help her get over the liver disease, and wished we could have done more for her.
