I’ve read about Leprosy a few times.
You seem to know much more about it than me.
Why are there no cases here?
There are. Certain “immigrants” bring a in few cases every year.
I don’t know the answer to your question. It may be a hygiene issue, or perhaps more virulent in certain populations, but I’m just speculating here. Also it may be here as well in which case they would be institutionalized and away from common view.