Dog preventative care is kind of a misunderstanding. We call things like flea, tick, and heartworm products preventative care but, honestly, preventative care is primarily an annual exam, at the very least, by your veterinarian to talk about adding certain prescriptions or making lifestyle changes at home.

Technically yes, and it's called the slow kill method. It is not recommended anymore. There's a totally different way of treating that now that your veterinarian has to do in a hospital.