We had 5 horses with pigeon fever a couple of years ago. Three had abcesses drained by the vet and two ruptured on their own. The gelding that was the worst happened to be staying at the vet's for an unrelated injury when the pigeon fever showed up, so we were lucky. None of the horses had any difficulties recovering and they all seemed more disturbed at the shots they got 2x a day than the disease itself. None even seemed sick or depressed. No other horses on the saee pasture have ever gotten it.