Dick B,
 
Although I have vaccinated many ferrets with Imrab Rabies Vaccine, I'v never
seen a ferret develop lethargy, anorrexia, weakness, and tarry stools 2
weeks after the vaccine is given.  Vaccine reactions generally occur within
24-48 hours after the vaccine is administered (usually within the first
hour).  These symptoms are classic of gastric ulcers in ferrets (and its
sounds like 2 ferrets treated for ulcers with amoxicillin and sulcralfate
responded).  If ferrets already have asymptomatic ulcers, and undergo stress
(coming into the new enviornment, diet change, vaccines) this could
potentially cause the ulcers to get worse and the ferrets start to show
symptoms (were there many stresses introduced to these ferrets at once or
were they in the shelter for a while prior to the vaccine?  You mentioned
that the pathology report was inconclusive.  I would be interested to know
if any pathology was seen in the stomach and intestinal tract (ulcers) or if
the pathologist looked for Helicobacter (the bacteria that cause ulcers in
ferrets).  Its always good to send the tissues to a Board Certified
Pathologist familar with ferret pathology like Dr Williams (who is one of
the most experienced ferret pathologists in the world).
 
These don't sound like vaccine reactions, but I would certainly recommend
you have your veterinarian call the vaccine manufactur to see if there have
been any similar reports.  If these were some type of unusual vaccine
reaction the use of benadryl (0.2 ml IM , 1 hour prior to vaccine) may help
prevent any reaction.
 
Good Luck,
Dr Weiss
301-299-4142
[Posted in FML issue 1320]