Avoid flea and tick powders, sprays, shampoos, foams, gels and wipes -- many contain pesticides that are dangerous for cavies. Read the ingredients. Some of these products have caused death. If your pet has mites, USE IVERMECTIN. When used according to directions and dosed carefully, it is a much more effective and safe product.
This excerpt is from this page of
Guinea Lynx :: A Medical and Care Guide for Your Guinea Pig --
Guinea Lynx :: Mange Mites
Zodiac Flea Shampoo contains permethrins, which are pesticides.
I hope there are no long lasting effects on your pigs.
I know several people from Canada who can find ivermectin. Why not post on
Guinea Lynx :: A Medical and Care Guide for Your Guinea Pig 's forums and see? There are a lot of Canadian members there who could help you find some, I'm sure.