My understanding is that mange is caused by mites and is only really a problem when the population gets big. I don't even touch any mangy dogs I shoot. I hear some guys say they bury them to stop the spread. That seems like a good idea however most of the time I'm coyote hunting
the ground is frozen and I don't have a shovel in hand.
In regards to dogs howling but not coming in it is my opinion that in those situations the coyotes have busted you and they're not coming in. I have only seen a few coyotes come in after howling. Mostly when they come in they are silent but not necessarily every time.