From:
Sukie Crandall
Date: 2001-04-25 14:53:00 UTC
Subject: Re: adrenal shocker
>
>Dear MC,
>
>I discovered adrenal disease (and insulinomas) in the 1980's prior to
>any published reports of these diseases and so have been tracking the
>incidence of these tumors longer than most people. There is no
>question that the incidence of adrenal disease has changed alarmingly
>in the decade of the 90's. I used to see 10 to 20 insulinomas for
>each adrenal tumor and adrenal disease was an occasional problem of
>older ferrets, mostly 5 or older. Now the adrenal tumors are more
>frequent than insulinomas, and start at much younger ages. Also I
>rarely saw bilateral adrenal lesions in the "old days", and these are
>common now. The only thing that has changed significantly in the past
>decade is the switch from small local breeding programs (where the
>ferrets were neutered at 5 to 6 months old), to huge breeding
>facilities where neutering occurs at a few weeks of age. The ferrets
>are still fed and housed by owners much as they were in the 80's, so
>day cycles, etc, do not account for the change in incidence. I
>suppose one could hypothesize heavy inbreeding as a cause, but the
>time span is probably too short to change the genetic pool that
>severely, and different breeders with different breeding stock all
>show the same problem. The only common link is early neutering.
>There was a ferret study in Europe in the past 12 to 18 months which
>claimed a direct link between age of neutering and adrenal tumors,
>although it wasn't a really good study protocol. Also a recent study
>in rats (who are not prone to adrenal tumors) produced adrenal lesions
>similar to ferrets when the rats were neutered very young. So, you
>have to draw your own conclusion, but there is no doubt that something
>has radically altered the tumor incidence in the past 12 to 14 years
>in American ferrets. It's not just "increased awareness" by
>veterinarians. I was very aware of the disease in the 1980's and it
>just wasn't that common. To my knowledge no other theory proposed,
>really adequately explains my observations over the past 15 years.
>Best Wishes,
>Mark Burgess DVM
Mark, you'll possibly recall talks about our Hjalmar who had adrenal
disease in the either the pre-FML days or early FML days. He was an
early neuter.
In fact, except for Haleakala we have had ALL early neuters, from an
assortment of breeding locations. Yet, we, too, have seen the age of
occurrence decrease -- that's over 19 years in a population of
practically all early neuters, and the rate of problem increase. For
this reason I suspect it's something else going on besides early
neutering (though I do suspect that any neutering increases the risk
of developing adrenal growths since they SEEM to possibly be more
rare in whole ferrets from the correspondence exchanged with many
people over those years). During the years that they became more
common multiple things have changed: the proportions of "fancies"
in the population has changed DRAMATICALLY -- partly in response to
past show emphasis of fancies and partly due to demand, nutrition has
changed from poor foods to the current ones, etc. If there is any
viral precursor as some vets have suggested then that could also have
increased in prevalence as the population of ferrets increased
rapidly.
Now, we are just one household so our experience could simply be
aberrant (sampling problem with sample size, etc.), but with us
having had early neuters for so very long, but STILL seeing the same
pattern as you describe I have to wonder if there is more to find.
As you noticed and mentioned: the study from the Netherlands had
some math and techniques that weren't up to recognizing patterns of
onset; I had some research mathematicians look at it, too, and they
said that the 3 and 1/2 year "pattern" wasn't really there. There's
the ENORMOUS slush factor (Could push a bus and the barn to put it in
through that gap.), the sampling techniques' weak aspects, etc. Now,
it might be that such a pattern could show up in a study designed to
look at that sort of aspect, but it wasn't what they were going for
in study design; they were trying to find out how common adrenal
disease was in ferrets and wound up wondering if they had a pattern.
They achieved what they had set out to do, and very likely their hint
that there could be a pattern warrants a study designed to actually
look at that, but the existing data is just not worth any conclusions
of patterns.
Having spoken with you a good deal "back when" I can verify that you
certainly were early on aware of a LOT of the problems which since
have become better known.