[Stefan-A]

They can weaken it and make it susceptible to other illnesses. They could probably spread diseases as well, but I don't think people are as concerned about that.

If you use branches, bark or other stuff you find outdoors, you might want to heat it or at least pour boiling hot water over it before putting it in the terrarium. New snakes should be quarantined and observed, especially if they are wildcaught.