Seresto Flea and Tick Collar WARNING

There should be an option for no stars. Yesterday I replaced my cat's SERESTO flea and tick collar. Within less than an hour, his hips and back legs were almost lame. He was walking with a typical post-anaesthesia gait. I called the Distributor, they never got back to me after a few tries. I called Bayer, I was looking for an antidote urgently. Eventually reached their Animal Health, eventually reached a person who had not left the company, no clear answer re antidote. Vet said it should wear off by today. No change. Nothing about this possible side effect in the package insert, I found it by googling.