My pigs had it on two or three occasions, including our own home born piglets vaccinated with the double dose of PorcEry at the correct ages. Each time we had a problem could be linked to having introduced bought in weaners to our own herd, or a sow had come back from visiting a boar elsewhere. The critical thing when you seen those symptoms, listlessness, loss of appetite and weakness in the back legs, is to take their temperature at once, and if it is very high, start antibiotics as soon as possible, within hours or minutes if possible. The pigs who got antibiotics really fast always made the fullest and quickest recovery, and their temperature would be down within 24 hours. We had quite a range of skin lesions - some very obvious raised, red, diamond shaped things, others just a bit of a red blob and others no skin lesions at all. Mostly, skin lesions came on later than the high temperature. Fortunately we never lost a pig, but the speed they go downhill with it if left untreated is terrifying. They all went on to be perfectly normal pigs, normal weight at slaughter and the usual delicious pork at the end.