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There is a delicate balance between fact and assumption. Here we will present what
we know to be true and what we are able to infer as high probabilities given our
extensive pedigree research into this disease. We expect more information to come
forward over time which may change our conclusions.
In October of 2006, SRI sent our pedigree review of
Siberian HCM to Dr Leslie Lyons. After she reviewed the documentation, the research was
forwarded
to Dr. Kathryn Meurs for DNA study and analysis. During this interim period,
we would like to provide breeders with some additional tools and insight.
Here we will review known facts of Siberian HCM and make some general
assumptions using those facts.
Preliminary pedigree analysis of Siberian HCM showed the disease had
multiple points of origin. The Moscow strain of HCM is only one
of four points where HCM seems to have originated in the
Siberian breed.
A general understanding of both HCM and cattery practices is useful in
demonstrating how it seems to disappear for generations. Due to the
greater number of cases, the strain from Moscow is easier to illustrate.
HCM is described as genetically dominant, variable expression, and delayed
onset. In layman terms this means:
- Only a single gene from one parent is needed for a cat to show symptoms or die from HCM.
- The severity and progression of the disease is not predictable.
- The first symptoms may occur at a young age or later in life.
Secondary genes may be present that suppress all symptoms or activate
the HCM gene. Presence of these “modifiers” or “helper genes”
are a strong part of the reason HCM seems to disappear or reappear
suddenly within a given line. It is highly improbable
that HCM spontaneously appears without a genetic component.
Cattery practices vary widely when it comes to disease or death.
Some catteries simply neuter breeding cats with heart murmur
and do not have echocardiograms performed. This is particularly
true in Russia, where ultrasound machines and veterinarian
cardiologists are very uncommon as well as expensive.
There are a few catteries that have knowingly continued breeding
despite the presence of HCM positive offspring. This is most
common where cats demonstrated excellent conformation, size or color.
A large number of cases have been reported on prominent
Moscow lines. High levels of inbreeding seem to be
responsible for the majority of deaths reported. Several maps
were created illustrating potential lines
where
the Moscow strain of HCM might have traveled. These charts
were
effective in demonstrating how HCM surfaces in irregular intervals,
but had severe flaws due to inbreeding with other types of HCM.
Of particular interest,
The most severe group of Siberian HCM has been tracked to a
cat in Germany. To date, we have been unable to track her
pedigrees into Russia, but are still researching the lineage.
In reviewing echocardiograms, two distinct
strains of HCM originated from St. Petersburg.
The milder type of HCM has only two known fatalities, but does require veterinarian
care. These cats are found primarily in Germany, as they originated from a
cat used as a foundation line there. These lines have recently begun to appear in
other countries more frequently.
Both St Petersburg and Moscow clubs have much older and more
extensive pedigrees than are generally available to the Western world.
At this time, the clubs in both cities have been less than forthcoming
with old pedigrees, nor do Russian breeders report HCM or early
deaths in their breeding stock. This information could be
crucial in the effort to isolate foundation cats
with HCM.
We encourage breeders to study HCM cases and compare
their current breed stock with known cases. While some
catteries have only a few potential carriers, others are
less fortunate. The ultimate goal is to eliminate this
and other genetic diseases from a cattery. If this is
not possible, then studs with no risk factors
for the disease should be introduced into the cattery, diluting
the genetic risks for HCM.
We encourage breeders to study HCM cases and compare their
current breed stock pedigrees with the pedigrees of known cases. Asking for echocardiogram results of the parents
and grandparents, veterinarian certification of the health of
parents, and a two-year warranty against genetic diseases is not
unreasonable.
Active SRI members who are concerned about HCM can submit pedigrees
to SRI for review against known lines. This might include your
current cats or potential breeders you would like to add
to your cattery.
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