I know two people that had dogs that they gave the monthly flea and tick treatment. Both dogs started having respiratory problems. The one had hind leg paralysis kind of similar to what you describe. They took her to a holistic vet in FL and was told that the medicine builds up in the dogs and causes toxicity. They went through a detox protocol and the dog recovered and was fine. Our friends said the flea/tick medicine causes respiratory paralysis in the fleas/ticks and an accumulation in the dogs starts to show similar side effects. I would try to find a holistic vet for treatment or some type of pet detox protocol.