In the first edition it is on page 225 first column about halfway down and I did not accurately enough recall the numbers: what it says is that after an outbreak occurs in ferrets who do not have sufficient immunity even if as many as 90% of the ferrets are vaccinated the disease will still infect a number, BUT if 70% or more were sufficiently immune then it was difficult to create an outbreak. The reference is Kelker, D The effect of immunes on the spread of distemper in small ferret populations Comput. Biol. Med. 10;53 1980 I knew it was in that edition so to save time did not check the second edition. Sadly, there is no abstract at http://www.ncbi.nlm.nih.gov/pubmed?term=Kelker%20distemper%20ferret and I do not find it for free online. Sukie (not a vet) Recommended ferret health links: http://pets.groups.yahoo.com/group/ferrethealth/ http://ferrethealth.org/archive/ http://www.afip.org/ferrets/index.html http://www.miamiferret.org/ http://www.ferrethealth.msu.edu/ http://www.ferretcongress.org/ http://www.trifl.org/index.shtml http://homepage.mac.com/sukie/sukiesferretlinks.html all ferret topics: http://listserv.ferretmailinglist.org/archives/ferret-search.html "All hail the procrastinators for they shall rule the world tomorrow." (2010, Steve Crandall) [Posted in FML 7110]