Although I do feel a bit moralistic about dog breeds that have been selected for specific physical appearance characteristics without much apparent attention given to the animals health. Pugs are a good (bad) example, the RSPCA takes a pretty dim view.[2]
Papillons have only minor health concerns although patellar luxation, seizures, and dental problems can be issues. Additionally they can be at risk for PRA, intervertebral disk disease, and allergies. [3]
It amazes me a bit that "dogs" are all the one species, Canis familiaris (which translates from Latin to 'family dog', cute). I wonder what we could do with humans if we selectively bread them for hundreds of generations.
1. http://www.abs.gov.au/ausstats/abs@.nsf/mf/7218.0.55 2. http://www.rspca.org.au/campaigns/pedigree-dogs/the-pug 3. https://en.wikipedia.org/wiki/Papillon_(dog)#Health
So the 2,000 that they have today doesn't say much about how many foxes they were breeding in the earlier generations (but over 50 generations the numbers culled probably do get into the thousands).