From:
RRC
Date: 2001-04-02 10:58:00 UTC
Subject: Re: Dr. Williams - Experience begets Understanding?
Edward Lipinski wrote:
>9.) Why is the incidence of 'cancer' so very much higher in USA pet
>ferrets than in other countries where ferrets are kept?
How do we know it is?
I have pondered this question for quite some time and I am not convinced
disease rates in the USA are much different than those in other
countries. To me, it is a lot like the supposed longer life spans. You
hear a lot of people claiming a lower disease rate or longer life spans,
but no one ever offers solid data to back up the claim. For the sake of
simplicity, suppose a disease rate is determined by the number of
animals seen by a veterinarian and duly reported. Is this an accurate
figure of disease in the ferret population? It well may be for those
animals which are owned by people who take their ferrets to vets, but
what about the population as a whole? What if a segment of the
population considers ferrets "disposable, cheap animals" and when they
become ill, simply euthanize them with a heavy stick rather than take
them to the vet? I believe (and I could easily be wrong) the subset of
people who take their ferrets to vets is larger in the USA than in many
European countries, which results in underreporting European ferret
health problems in comparison.
Ferrets in the United States are primarily kept as pets, and represent a
sizable investment of cash ($70-150). In some European countries, they
are kept as working animals, and can be as cheap as $20 or less. Any vet
on this list can tell you of the difficulty of trying to convince a
client that a $20 rat requires a $500 surgery; many clients will just
euthanize the rat and buy another. The point is, the incidence of
disease in European countries may be vastly underreported, just as the
lifespans may be over reported because sick animals are killed early and
not recorded. (I am NOT saying individual European ferret owners are not
as fanatic about their pets as American ferret owners; I am saying the
historic keeping of ferrets in Europe has not been as pets, but working animals).
It is typical to report disease rates per 1000 individuals (this number
can vary, but it is always reported), which I have not seen done for
either the USA or European ferret populations (this isn't entirely true
for the USA disease rates, but try to find them for European ferrets).
In other words, there is no way of knowing if the two disease rates are
comparable or not.
There is a second problem. Many cancers require a genetic disposition
AND an environmental trigger before they are expressed as a disease. It
is entirely possible both populations of ferrets (USA and European) have
identical genetic dispositions, BUT the USA population is being exposed
to more environmental triggers, so the disease is being expressed more.
So, ferrets in the USA have a higher cancer rate, but it is not due to
the genetics, but more to our particular way of care, housing or
feeding. That is IF there is a significant difference between the two
populations, which would have to be proved first.
One of the things I have been recently investigating is the history of
the ferret in the USA for the last century. I haven't yet traced the
origins of the ferrets which were used to start the big ferret farms
like Marshalls, but I HAVE been able to trace the origins of some of the
ferrets sold in New York and Ohio back in the 1880-1920s. More
importantly, I have strong evidence some of the ferrets sent to New
Zealand and Australia were from those NY and Ohio stocks (I can trace a
single release of ferrets in New Zealand from animals purchased in Ohio
at about 1913). The original NY and Ohio stocks seem to be a combination
of English and German imports, and the ties between the two regions are
extremely strong (I am currently trying to trace family members who
might have memories or papers which could document those connections).
The point is, I have come to wonder if inbreeding is a factor because
early American ferret stocks seem to have multiple origins and a large
founding population. Also, the early breeders were pretty ruthless, and
I suspect sick or weak ferrets were culled (as in killed) as soon as noticed.
I still am trying to document the origin of the ferrets that formed the
breeding nucleus for the large ferret farms (if it is possible; they may
not be willing to share that information). I suspect they came from
English, Scottish or German stocks, and if so, then I would expect
that—since it was typical and common to hybridize ferrets to
polecats—the inbreeding factor to be not as important as we might suspect.
That is not to say inbreeding ISN'T a factor. I'm just saying that there
needs to be some type of proof offered before we can assume the disease
rates are different. One thing is for sure; as some breeders attempt to
create new "types" or "colors" of ferrets, you WILL see an increase in
genetic problems. If you want an idea of the future of ferret problems,
take a look in the back of Kirk's Current Veterinary Therapy: Small
Animal Practice, almost any volume, and read about the genetic disorders
suffered by various breeds of dogs. Current ferret genetic disorders are
nowhere near the problems faced by pooches.
Personally, I think insulinoma rates are correlated to carbohydrates in
the diet, and adrenal disease is due to a combination of environmental
stress (cage stress, early separation stress) and neutering during early
development. I think these problems can be exacerbated by inbreeding,
but I would have to be convinced first.
Bob C