Vitiligo in Manchester mix

Question
I adopted a black Manchester mix,about a year ago and a few months ago I noticed some white flecks in her coat,no big deal at the time,so anyways she started getting more and as i parted the fur,I noticed the colour of her skin was also becoming white.So when she went to vet's a week ago they it's vitiligo,and while not comon,it's not uncomon either.And they also said her's is spreading more quickly than normally seen.she has been tested for other underlaying problems,and luckly so far she doesn't have anything else

And anyways here my questions,first is there any thing that can trigger it in the first place? She was adopted here in Canada but came from lousianna,and before she came up here she had Sarcoptic mange,heartworms,was pregnant and later found out she had a broken leg that healed on it's own.Could this type of stress trigger it? And the second is there anything I can do to slow down the spread? Right now it's a few spots under her chin,between her toes are white as well,and a number of spots on her back and it looks as if her muzzle might be next,as it's starting to get white hairs

Sorry if it's involved just wanted to gather as much info as possible-thanks for your time

Answer
The white flecks and vitiligo do not go together.  Vitiligo is an absence of pigment production in the basal layer of the skin.  The flake is surface skin.  That will happen in chronic skin infections.  I would first try 2-3 weeks of an antibiotic like cephalexin.  If there is a true vitiligo, then sometimes low dose steroids will help.  Your vet can do a skin biopsy to confirm the true vitiligo.