This work is not in ferrets and it is preliminary, but it appears that in at least one species the "common wisdom" that the immune system weakens with age may simply be wrong. Instead, inappropriate immune responses may be more common. http://www.eurekalert.org/pub_releases/2009-11/yu-ncf111709.php I just wanted to put this here because posts are so very often written as if a weakened immune system with age is to be automatically assumed, AND because I can imagine a mechanism where this could play into the increase of cases of anaphylactic shock at older ages compared to younger (besides there being more exposures), and because of the hefty titer levels our own older ferrets had when their CDV titer levels were done. 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 [Posted in FML 6521]