Revolution AND Ivomec both treat BLOODSUCKING and PARASITIC internal AND external bugs - that is, mange mites, worms etc.
Fido's treats NON-BLOODSUCKING external bugs - such as lice. It will also treat external bloodsucking bugs such as mange mites, but many of these actually burrow into the skin so the Fido's doesn't get to most of them...
Pigs scratch - doesn't mean they have any bugs...and one thing you don't want to do is overmedicate - if you treat your pigs too often for mites etc, then you can potentialy be breeding up a strain of mites that become resistant to the Revolution or Ivomec...Inital treatment for quarantine pigs (newcomers!) is a single dose of revolution, repeated every 3 months or so OR a weekly dose of Ivomec for a few weeks, then dose every 2-3 months as preventative.
WHenever I wash my pigs, they get some sort of preventative treatment. I only bath them every 2-3 months, and the first time I'll use Fido's -first a little of the Fido's shampoo, then the rinse - as prevenative against lice, then the next time I use Malaseb as treatment against possible fungal.