Rat Losing Fur???

[jasbus]

You say she was fine the day before? No obvious skin irritation? Then, my call is either mites, or overgrooming. With the little blood spots around the perimeter, it looks more like a grooming issue... I see little spots around her head as well, looks like more blood spotting. If you can check her fur around the neck and underbelly for more of these spots, it may be parasites.
But, judging by what you say, nothing the day before, I call grooming.

Another issue I find in rats and fur loss is, an improper diet. If their food source is not correct, they can get hot spots, just like a dog or cat. In rodents, it's usually from too much protein. It generally takes several months to become a problem though. Do you know what the breeder was using for rodent diet? Generally, a protein of 17--19% is perfect for rats, lower range if you're not breeding them. But, like I said, it usually takes several months for diet related issues to become obvious.

Ringworm usually starts with a little hair loss in a patch, then after several days, you see the classic ringworm and the hair comes off on that spot. And, the spot has a ring of dark around it. If the rats aren't scratching alot, it's probably an overgrooming issue. It doesn't look like ringworm, but I've been fooled before!

The only real other common fur loss issue is gonna be molting, but 90% of the time molting happens with the fine new fur already in place. Molting can happen in round spots that can "resemble" ringworm, and some people(Rasputin) will argue that can never happen, but every rat and every molt is different.

Personally, I'd cull the rat. Ringworm is very contagious, but sometimes you only see it in one rat, and it never spreads. But, it's not worth the few bucks to wait and find out in my opinion.
If you want to isolate her and just wait and see, it only takes a few days for the ringworm to totally be obvious. Any over the counter jock itch or athletes foot spray will cure it, but you have to wait weeks for the anti-fungal med to clear out before you can safely use the female again.
Feed her off, and move on, the easiest, safest and smartest way to get on with life in my opinion....