I never appoint doctors in the early stages of the game. When I have that few villagers, as soon as one reaches 14 I give them basic training in everything (including healing, but excluding parenting!). That means I can drag just about any villager to a sick villager and they will heal them without too much trouble. Doctors spend way too much time enjoying themselves for my liking and when everyone else is flat out working I just can't allow it Later on, when I have a lot of villagers, I can spare them to devote full-time to medicine.