>OK.  Time out.  I get really confused by discussions of allergy and
>allergic reacon the FML, but I hear physicians, nurses, and other health
>professionals misuse terminology, too.  Maybe someone can clarify things
>for me here.  I was always taught that a TRUE allergic reactions occur only
>when an animal is exposed to an antigen that it had been previously exposed
>to.  My immunology book characterizes allergic reactions (type I
>hypersensitivity) as follows: "Hypersensitivity is characteristic of the
>individual and is manifested on second contact with the particular antigen
>evoking hypersensivity."
 
I guess I am getting my introductory workout on this one. Jeff is absolutely
correct in his discussion on true allergic reactions. Most veterinarians
(M.D.'s, R.N.'s, etc.) use more common terminology (e.g., allergic reaction)
to their clients to convey what is comfortable and understandable to the
clients.
 
A true anaphylaxis (i.e., allergic) reaction requires that the pet (or
person) have been sensitized to the offending allergan (a protein,
carbohydrate, etc.  that induces an allergic reaction.  Also termed an
antigen.) at least once prior.  This exposure can occur as shortly as two
weeks before or as long as years before.  The technical department at Rhone
Merieux (makers of the Imrab3 rabies vaccine) also takes this view when you
discuss rabies vaccine reactions.
 
Also understand that the preservatives or adjuvant (the stuff that makes the
vaccine more likely to elicit an immune response to protect the ferret) may
also cause anaphylaxis. Many vaccines contain the same or similar adjuvants
and/or preservatives.
 
In New Hampshire, all ferrets are typically sold with at least one distemper
vaccine given prior to the sell.  Hence, most of the ferrets I see might
already have a prior exposure to an allergan.
 
More to Jeff's point.  In a ferret whose has never been vaccinated before,
any illness that results from the first vaccine cannot, by definition, have
a vaccine reaction.  Serum sickness is also unlikely since we are seeing an
acute response and serum sickness is usually a later type hypersensitivity
reaction.
 
So what is causing the reactions in the ferrets receiving their first
vaccines?  A couple of possibilities.  First, a true allergic reaction may
be occurring.  Response to anti-histamines and/or steroids reverses the
symptoms quite quickly leading me to believe that a histamine release type
of reaction is occurring somewhere in the ferret.
 
Second, the vaccine (and associated stuff) may be taken up in the
bloodstream too quickly.  Certain chemicals, etc.  when given intravenously
might induce low blood pressure, mimicing an allergic symptom.
 
In my experience, most all the ferrets who have had an allergic reaction
have been vaccinated before.  From a practical point of view, they are all
treated the same (see the posting a couple of days ago).
 
Hope that helps clarify things some.
 
Schedule of vaccines (at least at my Hospital).
 
Distemper (young ferret)
6-8 weeks of age
12 weeks
16 weeks
Then once yearly.
 
Distemper (older ferret who has never been vaccinated or history is
questionable) one vaccine now, repeat in 4 weeks.
 
The main point is that the ferret needs at least two vaccines 1 month apart
with the last vaccine being when the ferret is at least 16 weeks of age for
initial immunity.
 
Rabies
16 weeks of age (or first visit if older than 16 weeks) Then once yearly.
 
Mike Dutton, DVM, DAVBP
Weare Animal Hospital
Weare, NH
[Posted in FML issue 1412]