just to add on Lankeela's comments, a Pyo is generally more common on older dogs, and starts anytime from a month after they finish their season. But is not always the case, I had a nine month old bitch, on her first season, all was normal until her last day. She was still eating, did not have a temperature, but was sick,...just once, and she kept lying outside not wanting to come in the house. I wanted to be sure she was ok and asked the vet to scan her, and she had a closed pyo. The vet had never seen one on such a young dog, and we were so lucky to catch it early.