I have a number of types of Lycanthropes, and I don't tell the players what type they've run into, they have to figure it out:
Curse: may be Transmittable or Confined (non-transmittable)
Disease: treated as a blood disease
Birth: racial sub-type, may be transmittable or not
There can be overlap, a player in a friends game is suffering from a curse one of his ancestors acquired: it is only passed down through the male descendent's. This is primarily a confined transmission curse, but it is also by birth.
The disease form can be treated as an STD, where it may not only have a chance to infect the mother, it also has a chance to infect the child (which is a good explanation for where birth lycanthropes originate from)