Re: How to treat for mites?
I'll make this a sticky about treating for mites.
See below for how to tell if your pig has mites.
Don't bathe a pig that you suspect has mites. The water drives the mites crazy, and the mites drive the pig crazy.
Pigs over 350 grams can be treated with ivermectin. Pups who weigh less than that can take kitten Revolution, which requires a prescription from a vet in some countries (including the U.S.) but not others.
This is the easiest stuff to use:
http://www.amazon.com/Ivermectin-Pour-On-For-Cattle/dp/B00JAL3AAW/ref=sr_1_3. (In case this link breaks, it's Durvet Ivermectin Pour-On for Cattle, with 5 mg/ml of ivermectin.) It's the easiest to measure, and the hardest to overdose a pig with.
You need to know how much the pig weighs, in grams.
This is the dosing chart and the instructions for applying the ivermectin:
http://www.guinealynx.info/topical_ivermectin_pour-on.html.
More information is available at
http://www.guinealynx.info/search_ivermectin.html and
http://www.guinealynx.info/search_mites.html.
How to know if your pig has mites:
You can't see them on the pig. They're very tiny, and they burrow under the skin. There is no test that will diagnose them for certain, not even a skin scraping. Those are painful for the pig, expensive for you, miss the mites half the time, and the end result is the same as if you hadn't tested: treat for mites.
If your pig is insistently scratching and you can't see any bugs crawling on it, and there are no lice nits stuck to the hair, it's probably mites. The GL links show some pictures of typical hair loss with mites.
Edited to add: Treat all your pigs once a week for three to four weeks. Apply the medicine (it doesn't matter whether it's the pour-on or injectable kind) in the bald spot behind the ear, fold the ear over and massage it in.