About a year ago I was raising mice in a 10 gallon glass tank with a screen top. I was out loading hay in a barn and found a nest of mice pinkies and decided to bring them home and put them under my feeder mouse to raise up. Let me tell you those mice were something else, they were so fast in the tank that there was no way I was going to catch them by hand. And it's not because they grew up in the wild, I'm pretty sure our common domesticated mice are bred to be very slow moving. These wild mice were so fast the only way I could get them out of the tank was to seal it up and gas the whole thing with CO2. I'll never mess with wild mice again.
In addition to considering parasites and poison, you have to understand that your snake is eating anything that the mouse ate -- and mice eat practically everything -- and some of those things can be quite toxic to snakes.
Remember, your snake isn't getting a choice in this. It simply eats what you put in front of it -- to its nourishment, or its peril. And THAT, is your decision!