When and where was syphilis originated?

The truth is we are not yet sure about the origin of Syphilis. Both Greek and Roman writers as well as later European writers described "leprosy" diseases that could have been Syphilis, though this is speculation.
It is often believed to be a New World disease which came from another disease known as Yaws. One reason for this is that the first well documented European outbreak began a few years after Columbus and his men returned from the new world.

At this point there doesn't seem to be any good reason to blame sheep, the French, or French sheep for the disease. Though if you've ever seen Woody Allen's "Everything You Always Wanted to Know About Sex, But Were Afraid to Ask," you already know how a sheep can look in French underwear.

So make your own decision, but first read this short article supporting the New World origin theory. It describes how we are trying to uncover the truth:

http://www.archaeology.org/9701/newsbriefs/syphilis.html