Why take the risk, use a piece of wood you know is safe, if you do decide you want to use it, at least bake it or pour boiling water on it to kill the parasites and scrub it down with steel wool.
Hmmmm... I would be hesitant with anything from the outdoors. If you choose to do so, then I would highly recommend first soaking it in a 15% bleach solution for atleast an hour, then baking it at around 350-400*F for another hour or two before putting it in with your leo.