We have seen this at Ferret Wise on a 2 year old late alter ferret that
was turned in w/o vaccination information.  The rabies vaccine was
administered ( for adoption purposes) and the ferret nearly died.  Just
moments after injection ( yes benedryl had been pre-treated) the ferret
started vomiting first white foam then blood at the same time blood
poured out the posterior end.
 
The vet immediately injected epinephrine once, and then again and the
ferret was ultimately near dead for another 2 hours.  We finally left
( the ferret & myself) when it looked as if the ferret would survive.
However it was almost 6 months before the ferret was eating right due
to a hepatic condition which resulted.
 
Anaphalaxis is VERY scary it also can leave a ferret with health
impairments--- and we have never vaccinated a marginal ferret since
that date for either rabies or distemper.
 
Alicia
www.ferretwise.org
[Posted in FML issue 5161]