Canine Distemper Virus (CDV) is a risk to ferrets, from contact with bodily fluids (snot and eye discharge) & urine & faeces of infected animals. Domestic cats seem to be immune but unvaccinated dogs can transmit the disease, as can foxes. CDV will generally be fatal to ferrets, slight chance of survival if treatment given early enough, but highly unlikely.
You can vaccinate your ferrets against CDV, lasts for about a year, maybe 2 years. No real answer as the vaccine isn't designed for ferrets. Only drawback is the vaccine can also be fatal for ferrets due to an anaphylactic shock