It won't have a negative effect on your snakes, but you should fix the problem. It's not right to ignore the problem, just because they are going to be fed off (not that that's what you're doing) You'll probably have to start over, with new stock. Healthy stock should basically never get sick.
I haven't had any health issues in my mice in over a year.
What kind of bedding are you using? Are you keeping your rats outside? Do they havep roper ventilation? Is there any blood on their noses?