There are many internal parasites that wild mammals carry.
Some live in the tissues, some are intestinal. (Roundworms, hookworms, whipworms, tapeworms, heartworms)
Dogs and cats get these parasites all the time . Not sure if these particular parasites would harm a reptile,
but it would be very common for wild mice to harbor these parasites.
And all these parasites are specific to North American field mice? They aren't found in any other animals that are eaten by snakes anyplace in the entire world?
I may not be very smart, but what if I am?
Stinky says, "Women should be obscene but not heard." Stinky is one smart man. www.humanewatch.org