I'm sorry to hear that. It's very important that you quarantine that pig as soon as possible because it will spread quickly. There are three agents that can treat the pig: carbadox, lincomycin and tiamulin. Try to get your hands on some of that. Honestly though, it might be less expensive to kill the animal and count it as a loss.
Oh no! Do you know how they got it? I think it often occurs when the pigs eat contaminated fecal matter from rodents, so clear that up if you rodent problem. Muck out their area and keep it meticulously clean for a while. I hope you're able to make some headway. I wish you lots of luck!