I mentioned there seemed to be at least two different things going on in
ferrets, resulting in adrenal disease.  Mind you, there may actually be
more, but from the data collected and the stuff in print, I think right now
all you can safely say is more than one factor lurks behind this disease.
So what is the implication of "more than one?"
 
Before we answer, let's address the question of what can *cause* adrenal
disease.  One of the first steps to any scientific investigation is to try
and limit the study to the possibilities, rather than the "but what ifs..."
So, making the assumption that adrenal disease is initiated by some sort of
abnormal growth within or adjacent to the adrenal gland, what basic things
could cause it?
 
The list could include genetics, environmental pollutants, diet, body
condition, stress, chance, or even that the disease is a species "weakness"
(like how specific diseases tend to be more common in certain animals than
others).  While some people may be convinced that only one of these is the
"real" reason, remember I said the disease appeared to have at least two
different manifestations.  Now do you see the implication?  It suggests at
least two factors may be responsible.  These two factors could be linked, or
they could be independent, but only scientific testing will ever prove the
relationship--or the reasons--one way or another.
 
I believe there is a genetic component involved; those that kept track of
their kits noticed adrenal disease sometimes ran in family lines.  The
statistics are very poor for this because few breeders care to follow the
babies they pump out.  This is a shame, because it is quite conceivable that
vigorous and healthy hobbs and jills may be spreading a recessive trait
within the population.  This is what all the hoopla about blood lines is all
about, as well as the "Marshall Farms Hypothesis," (being that MF ferrets
are predisposed to adrenal disease).  If you accept the idea that
non-American ferrets have a very low incidence of adrenal disease, its quite
easy to point the finger at the DNA and blame it, when in fact there may not
be any relationship at all and the reason could be because of some other
factor within the US and Canadian populations.
 
For a moment, lets assume it is genetics.  Do MF ferrets have a higher
proportion of adrenal disease than other ferrets?  Not if the people who
sent data are to be trusted.  About half of the ill ferrets did not come
from MF at all.  Assuming MF supplies about half of the ferrets for the pet
market, if they were more prone to adrenal disease, there would have more
cases reported in proportion.  The reported statistics suggests parity; in
other words, it seems as if all "brands" of ferrets are equally susceptable
in contracting the disease.  (I don't know what the actual percentages
regarding how many MF ferrets are produced compared to other breeders, nor
do I supect anyone does because few breeders report their kit placement.  If
you disagree with my assumption that 50% of ferrets are MF, then by all
means provide a substantiated source).  One thing that has struck me is the
apparent inability of people to look past what the numbers *are*, and see
what they *mean*.  For example, suppose 100 ferrets are MF and 100 from
other sources.  20 ferrets get adrenal disease and about half are MF.  That
is parity because all populations contract the disease equally.  But what if
150 ferrets are MF and only 50 from other sources and out of 20 cases, 15
are MF and 5 are other?  Well, that's STILL parity, but it appears MF
ferrets get the disease more than others; after all, its 15 to 5 right?  The
result is many people point out the majority of adrenal cases occur in MF
ferrets, but they never correct for the proportionality of breeder
demographics.  And even if Path Valley, MF, and all the other major breeders
opened their books to our inspection, it would still be useless until you
figured out how many ferrets were coming from unnamed hobby breeders.
 
The underlying assumption behind the idea that New World ferrets get adrenal
disease in higher proportions than other ferrets is that some sort of
founder's effect or breeding bottleneck has taken place.  In other words, if
true, then some breeders have inbred their ferrets so much that a genetic
mistake has become visible.  This looks good on paper, but I don't buy it
for many reasons, especially two major ones.  First, look around you; you
see albinos, sables, silvers, dark eyed whites, and so forth.  Body sizes
are small to large, whippet, standard and bulldog.  The amount of variation
within the USA ferret-line suggests inbreeding is not a problem.  Remember
the old biological axiom; the older the species, the more variation, the
older the genera, the more species, and so forth?  Of course the exceptions
are lines that are dying out, but that is not a problem in our furry
mustelids.  We have *LOTS* of variation.  If inbreeding is a problem
anywhere, it would be minor and essentially isolated.  Support for this
contention comes from there being absolutely *NO* significant difference in
the numbers of one type of coloration or of body type being predisposed
towards adrenal problems.  Albinos had adrenal problems about as frequently
as sables.  I only had 87 reports of coloration, so obviously the sample is
small and better investigation may find such a link....maybe.
 
I also think the idea is flawed simply because the ferrets in the USA came
from Great Britain and Europe, precisely where the ferrets in New Zealand
and Australia came from.  Those populations tend to follow the basic
European lead in lack of adrenal disease.  Remember, we are assuming
accounts of rare adrenal disease are factual, and without contrary evidence
such assumptions are valid.  I also have to say that in reading dozens of
European ferreting books published during the last 80 years, every medical
ailment from blackheads to distemper to swollen prostates to torn nails is
discussed, but significantly, no mention of a class of symptoms that could
be interpreted as adrenal disease is mentioned.  These "ferrets and
ferreting" books include three from Germany, one from France and 17 from
Britain.  I've noticed the same pattern in American ferret books; the
mention of adrenal disease only dates back slightly more than a score of
years ago.  Like I said, interesting.  Considering the slow acting nature of
the disease, if it was a common problem, it would have been mentioned in one
of these books.
 
The same is true in the veterinary literature.  I scoured every possible
source, from data bases to biological abstracts to the journal indices to
books.  Nothing in the laboratory papers, nothing in the literature *UNTIL*
about a score of years ago, and those reports were almost exclusively
American in origin.  This lends great support to foreign claims that the
disease is largely an phenonmenon of the Americas.  This is not a claim that
should be ignored nor dismissed.  Remember this for later.
 
Back to the idea of founder populations in the USA/Canada, Australia and New
Zealand.  Modern day populations in all three countries had origins in
initial founding colonies that date to the turn of the century.  In
Australia and New Zealand, except for a handful of exceptions, the present
populations are essentially direct descendants from those founding ferrets,
and adrenal disease is rare.  In the USA, because of the ratting industry
from the 1880s to the 1920s, the initial populations were supplanted several
times from fresh European stock.  Now, understand, founder effects take
place because a breeding restriction took place which shifted *EXISTING*
gene frequencies, or introduced a new mutation into the breeding pool; if it
isn't in other populations, then it must have been "invented." Now, this
begs the following two questions.  If the problem preexisted, why hasn't it
shown up as much in non-New World ferrets, especially those with similar
founding populations?  And if it is a New World specific mutation, why is
only now showing up and not 40 years ago?
 
This is the trouble.  Ever try to introduce a new trait into a population?
It takes time; considering the existing range of variation in body types,
coloration, color patterns, and sizes, there is virtually no possibility
that such a trait could have become established in such a large population
is such a short time; if everyone looked about the same or the variation was
limited, weeelll maybe.  Of course, this is assuming the trait is recessive,
which it has to be because more than 70% of you stated the trait does not
effect all siblings in a birthing, and if it were dominant, it would.  (Of
course, the jill could have been bred to more than one male, but that is not
common in USA breeding practices, and induced ovulation makes it basically a
moot point).  So, if adrenal problems are genetic, it must be something
brought in with the original founding ferrets that only affected USA
populations, or something that started within a few generations of the
founding of USA populations.
 
But Bob, didn't you say you thought adrenal disease had a genetic component?
Yes I did.  The truth is, I'm beginning to wonder if the disease doesn't
parallel a similar situation in some forms of human diabetes.  In Native
Americans, diabetes is quite common, but in earlier populations it was never
manifested.  So a group of people lived in the Americas for 12,000+ years,
and diabetes was rare.  Europeans come over, teach the locals how to eat
better food, and the locals respond with obesity and diabetes.  In this
case, there is an demonstrated underlying predisposition for the disease,
but without the proper environmental factors, the disease never comes out.
 
Its the old "nature-nurture/genotype-phenotype" debate.  And it makes
perfect sense.  Why is human cancer so difficult to control?  Because, in
many cancers you don't get cancer unless you have the predisposition AND are
exposed to an environmental stimuli.  That is why some smokers get lung
cancer and others merely die from emphazema or heart disease.  Smoking is
the environmental component, but some studies have shown that a genetic
component is present as well.  Remember the last post (and the top of this
one) where I said the adrenal problems seem to have more than a single
causality?  This would go a long way in explaining why more than 60% of you
said your adrenal ferret was currently in or came from a shelter.  This
suggests some sort of commonality that is causing this predisposition to
manifest itself.  What if the environmental component (if indeed this is the
case) was something that was common in the USA/Canada, but rare in Europe,
Australia and New Zealand?
 
Could this help explain 1) why adrenal disease is so common in the New
World; 2) why, with the introduction of USA practices, adrenal disease seems
to have been lately increasing in Britain; 3) why the disease appears to be
common in animals exposed--in mass--to similar environments, such as in
shelters or mass groups in pet stores; and 4) why the disease responds
poorly to non-surgical treatment (because even with the treatment, the
ferret is *still* exposed to the triggering factor)?  Stay tuned for further
details when Bob pulls down his shorts and dares all to light their
flamethrowers.
 
Bob C and 20 MO Socksharks
[Posted in FML issue 2218]