I rescued a gp that had all the typical mange symptoms including seizures even multiple times a day and it had been treated with ivermectin, even more times than usually needed I understand, but it wasn't helping so the vet suggested that the pig should be put down.
That's when I luckily ran into the pig and offered to take him home with me, where I took my chances and treated him for skin fungus (I've had experience with it before but nothing this bad) which was regular washing every few days with nizoral shampoo. Also I had multiple open sores to worry about that was the hard part in treating him.
Just see how the ivermectin affects, unfortunately there's not much to do for the itching if it is mange mites because anything moist or vet makes the creatures crawl deeper and that's painful for the pig. In a fungal chase I found that coconut oil eased the itching a lot.
Here's a picture of my boy to brighten up the day
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