Dear MC:
 
>There has been a discussion on pre treating ferrets before their distemper
>shots and in that discussion a comment was made to the effect that if
>a ferret is pretreated with an antihistamine, the effectiveness of the
>distemper shot would be decreased, due to the body setting up its
>defenses via the antihistamine.  The exact statement follows:
 
>>In general, pre treating reduces immune response, thus reducing the
>>effectiveness of the vaccine, or causing a harm.
 
I didn't make that statement, and if it is being ascribed to the use of
anithistamines prior to a vaccine, then it is incorrect.  Pretreatment
with antihistamine does nothing to reduce the APPROPRIATE vaccine
response - the desired long-term immune boost which we want from our
vaccine.  Corticosteroids, which I have heard INCORRECTLY advocated as
part or pretreatment on the FML, DO profoundly impact on the ferrets
ability to respond properly to vaccine and have no place in a pretreatment
protocol.
 
What we want is an immune-stimulatory reaction to a vaccine, not an
allergic one.  Histamine is the prime substance in the generation of an
allergic reaction - and allergic reactions usually happen within minutes of
exposure in sensitized individuals (other terms for this allergic response
are immediate hypersensitivity, or anaphylaxis).  Anti-histamines, like
benedryl, block the histamine receptors in the ferret's body so that even
if there is an allergic reaction and widespread release of histamine, its
systemic effects are minimized.
 
Corticosteroids, on the other hand, actively decrease the immune system of
the ferret over a long period of time, and this diminished immune system
may not be able to respond properly to the vaccine.
 
Antihistamines are acceptable for pretreatment, steroids are not.  This
is not to say that animals on prednisone for insulinoma or other problems
cannot be vaccinated; but it means that we have to watch the dosage very
carefully.
 
>This is a clarification of that statement:
 
>Certain drugs, such as corticosteroids, are known to adversely affect
>titers in study animals, sometimes leading to infection.
> MMWR Vol. 45 / No. RR-12, p. 18
 
This statement is correct.
 
>W/ other drugs, effects are suspected but unknown/unproven, and for this
>reason only healthy animals are used in studies, w/ no pre-treatment or
>other variables allowed.  Thus, animals pretreated in the field are not
>following vaccination protocol and the results of the efficacy study do
>not apply to them.
 
Antihistamines are not mentioned here - it seems that we are talking about
steroids once again.
 
>My sources for the paragraph above are conversations w/ Charles Rupprecht,
>John Krebs and Michael Niesgoda at the CDC, and Jeannine Gilbert at then
>Rhone-Merieux.
 
It is appropriate in scientific studies - in this case for the rabies
product - not to pre-treat.  Remember however, they were not gathering
information on anaphylactic reactions in ferrets, but addressing the
vaccination protocol for a rabies vaccine in ferrets.  You don't want to
mix apples and oranges...
 
>And, I suppose this also leads into, What is your take on pre treating
>ferrets in general before a distemper vaccination, even if they have
>never shown any sign of reacting in past shots?
 
I am rapidly coming to an opinion, based on the tremendous variation
of vaccination practices out there in the community, of recommending
anti-histamine pretreatment for all distemper shots, all animals.  Benedryl
is cheap and has a high margin of safety in ferrets.  Most vets have it
handy, and even shelter operators can give an oral dosing.  It doesn't hurt
ferrets, and likely saves lives (we'll never know though - if it's working,
the animal doesn't react.)
 
>Dr. Williams, this is a real situation out here in the ferret world.  More
>and more, our gentle readers are really starting to question whether or
>not to vaccinate against distemper out of fear of reaction..even though
>they know that if their ferret gets distemper, it is 99.9% fatal.  As a
>local vet has stated, we ferret owners are damned if we do, and damned if
>we don't.  Not a pleasant spot to be in.
 
No offense taken to this statement, although your implication that I live
in an ivory tower (located far away from the "ferret-world") is noted.  I
have had ferrets for years as members of the family (as many as eight at
once), and I currently have three (recently adopting two with health
problems.)  I vaccinated them upon receiving them, pretreateding, and using
Galaxy D.  I held my breath for an hour just as every other ferret owner
does.  I fully understand the possibility of reactions to any vaccine in a
ferret, not just Fervac.  I fully understand that I was taking a small risk
of having a life-threatening reaction in a normal healthy animal.  But I
have also seen ferrets die of distemper, as I have seen cats die of Feline
Leukemia, and humans die of AIDS.  My business is disease and death, and my
job is to turn it into knowledge that people can use to prevent or treat
it.  Distemper is a miserable way for a pet to die, and it says, above all
else, that a human has slipped up in their responsibility.
 
Right now, people who have had reactions are recounting their tragedy to
the FML.  Let there be no mistake, these reactions are heartbreaking.
However, this is still a handful of individuals.  And the accounting is
wrong - let me explain.
 
I have received email from several people taking issue at my assessment of
the reactions to Fervac at around 2%.  Some people have had three of six
ferrets react.  (That's 50%!)  However, what we don't look at is if you
have five ferrets at five years each, and they have been kept up to date
on distemper reactions, and one reacts - that's three vaccs the first year,
and one each year since then, for a total of thirty-five vaccinations (or
about a 3% incidence) not 20%!
 
Is everyone posting all of their reactions?  - probably not.  But how many
people are currently posting about their LACK of reactions - only three
that I have counted - Bill and Randy and myself - and they have literally
hundreds or thousands between them.  And if all of the other shelters spoke
up, this story would probably play out over and over.
 
I hope no one else will be thinking that I am an apologist for Fervac-D,
or that I am out of touch.  The FML is a wonderful tool for disseminating
information, but it magnifies the incidence of many diseases, as it is
right now magnifying vaccine reactions, and scaring people away from a
necessary vaccination.  Posts are emotional - there is no requirement for
responsible journalism on the FML, nor should there be.  We use terms like
KILLER VACCINE to describe Fervac-D - what are people to think?  A two
percent reaction to a vaccine is HUGE - most vaccines run around 0.01 -
0.001 percent.  But that doesn't make it a killer vaccine, especially
when most reactions are treatable, and possibly even preventable.
 
If people are being frightened away from distemper vaccination, we have
only ourselves to blame.  There are other products available, and
recommendations to minimize reactions.  Be educated, be logical, and
vaccinate.
 
Bruce Williams, dVM
[Posted in FML issue 3240]