Hair Loss bald patches on new pig, no scratching

[pigs down under]

Hi
I got a new pig (Rosie) 3 weeks ago and have started introducing her to my other 3 pigs. I was petting her yesterday when I noticed her fur (she is a smooth hair with quite a glossy coat) was uneven in 2 places. She has 2 bald patches about a centimetre and a half across but didn't seem at all uncomfortable with them being touched. Should I give all the pigs mite spray as a preventative just in case? We were at the vet less than a week ago for another pig and took her for a check up too. The vet checked her over and either didn't notice or wasn't concerned about the bald patches. She is an older female but I cant feel any cysts. Any idea what it could be?
Thanks

 

[bpatters]

First, I wouldn't spray for mites. I'm not a fan of spraying pets that groom themselves, because they'll inevitably get some in their mouths.

Second, the top lesion doesn't look like mites, but the second one and its location does.

I'd do two things. I'd get some antifungal cream or lotion, like Lotrimin, and apply it with a q-tip twice daily for several days and see if that does anything. Fungus and mites often coexist, and the antifungal cream won't hurt even if it's not a fungus.

Second, I'd treat with ivermectin. You want the .5% pour-on or the 1% injectable (DON'T get the cattle/horse paste). Apply either in the bald spot behind the ears, fold the ear over, and rub in well. Here's more information on how to do it: https://www.guineapigcages.com/forum/threads/111160-How-to-treat-for-mites-and-lice