ForestWind Siberian Cats
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HCM in Siberians
Unfortunately, there have been some unscrupulous breeders who purport to be able to predict which Siberian cats will develop HCM. They are following a flawed practice and have been blacklisting certain Russian catteries and breeders who work with those lines. Through intimidation and insinuation they have been spreading their "facts" widely. It is sad that rather than focussing on healthy breeding to type they have chosen to concentrate on pseudo science.
What can you do as a Pet Buyer to guage risk? Ask to see copies of your proposed kitten's pedigree; ask your breeder about any genetic diseases in the pedigree; and request the coefficient of inbreeding (COI) percentage for the litter you are looking at. This percentage tells you how closely related a cat's relatives are.
COI is easily calculated. In order to set type in a young breed, some breeders have elected to move quickly to linebreeding or inbreeding. This means breeding cats together who are related to each other. While some breeders will tell you linebreeding and inbreeding are different practices, in actuality they are the same thing. The artificial separation that is claimed is that linebreeding is breeding less related cats together, and inbreeding is a practice of breeding very close relatives together, such as sibling-sibling, parent-child, or grandparent-grandchild.
If a breeder practices inbreeding, they collect together similar traits. This is beneficial in terms of getting cats to resembe each other ("Set type"), but is a negative practice in terms of maintaining the genetic diversity necessary for a healthy breed. When genetic diversity is descreased, the chances of a cat "collecting" a set of disease genes is heightened. This appears to be true for HCM. The more clsoely related a line of cats is the higher the chance that breeding them together will create disease. This is not an issue restricted to Russia, or any country. Instead it is related to individual breeder practice. Rather than relying on innuendo or psuedo science, be sure you look into the health of the relatives of the kitten you are considering adopting.
Our Practices
We contribute monthly to a WINN Foundation fund for HCM research in Siberians.
When this research generates reliable data, it will be shared here. Until then, ForestWind Siberians works with their veterinarian to check all breeding cats yearly for observable signs of HCM, as well as ascultate them to detect potential heart sounds indicating health problems. Any breeding cat that is found to have signs indicating HCM will be removed from our breeding program, and all kitten owners will be notified. Additionally, we strive to pair breeding partners whose litters are COIs of 5% or lower. While this results in a slower trip to "winner's circle" in the show hall, it also protects the entire breed for many generations to come. We beleive that individual and breed health and temperament should be the number one priorities of any person committed to cat breeding.
Below is information from a UC Davis Researcher who has been studying health problems in felines for many years. She explains about HCM in cats and steps breeders can take to get involved in research.
At the bottom of this page, there is a link to an HCM Study and Support Group for Siberian Cat Breeders to join.
As a prospective ForestWind kitten owner, it is important for you to know the steps we take to keep our cats and kittens healthy and vibrant.
About Research on Heart Disease
The most common types of
heart disease found in cats are dilated cardiomyopathy (DCM) and hypertrophic
cardiomyopathy (HCM). DCM is associated with taurine deficiency in cats, while
the cause of HCM in cats is genetic or has an unknown etiology. The
presentations of these two diseases are easily distinguished by ultrasonic and
ECG examinations. Both diseases are progressive but only DCM can be corrected by
dietary supplementation. Heart murmurs are also common in cats, but of
different severities. Although a murmur is indicative of a heart abnormality,
they do not indicate the exact type of the heart problem. Most congenital
murmurs resolve (in kittenhood) and are generally no more severe than a
Grade Y murmur. (Murmurs rank from Grade 1 to Grade 3 being the most severe).
Thus, persistent and severe murmurs generally do indicate a heart abnormality.
Researchers have studied
both DCM and HCM in cats for many years. HCM has been proven to be inherited as
an autosomal dominant, single gene in Maine Coon cats. But, this DOES NOT mean
that all murmurs indicate HCM in cats and DOES NOT indicate that HCM found in
other breeds is the same genes as found in Maine Coons. The genes could be
different in different breeds. Since the genes could be different, there may be
more than one gene in a particular breed that causes HCM, and the inheritance
pattern may be different. If a gene is found for one breed, it would have to be
tested in the other breeds that have heart abnormalities
The clinical presentation of
heart disease makes it a very difficult trait for genetic study. Heart disease
often presents early as a murmur, but many cats with HCM do not have audible
murmurs. Genetic traits generally have early ages of onset. HCM has been
detected in cats from X to Y years. The disease can be very mild or very
severe, but both can be associated with sudden death. Veterinarians with
different training and equipment often do not have consistent diagnoses for the
same cats with heart disease, thus this can complicate the collection of
accurate samples. Thus, genetic studies can suffer when mildly affected cats
are diagnosed as normal (false negatives). Inaccurate data makes it difficult
to determine how a disease is inherited and if it is a single gene or a
multiple gene affect. A cat may have the gene that causes heart disease but has
such a mild presentation that it is undetectable, this is known as Incomplete
Penetrance. Although Incomplete Penetrance can be estimated, it also causes
inaccuracies, which can only be overcome by larger sample sizes.
There are a variety of genes
that have been shown to cause heart disease in other species, including humans.
At least six genes cause HCM, thus, each of these genes are strong candidates
for feline HCM. These genes are being analyzed in HCM found in Maine Coons.
This type of genetic approach for testing a known heart disease gene is called
the "Candidate Gene Approach". Although a very valid approach, this
type of study is often assisted by other genetic studies.
A second approach that supports the Candidate Gene Approach is called an
"Association Study". These studies make use of samples from affected
and absolutely normal cats only, samples are not collected from complete
families or pedigrees of cats. This is a valid approach for HCM in cats because
of the difficulties in disease diagnosis and sample collection. Although an
affected cat can be identified, it is often difficult to collect samples from
all the related cats and even more difficult to get high quality and accurate
heart examinations. Genetic studies are highly compromised by inaccurate and
missing information. Unfortunately, association studies generally require hundreds
of samples, both normal and affected, in order to be statistically powerful.
A third and very common approach to detect the genes causing a disease is a
"Family or Linkage) Study". Family studies require at least three
generations of cats to be completely sampled and to have repeated clinical
examinations. This approach is very common for diseases that have a clear
inheritance pattern, are caused by one gene, and are frequent in the
population. Often, a few large and dedicated catteries will supply information
for several years to contribute to a Family Study. Often, investigators will
establish their own breeding programs to develop the pedigrees for a Linkage
Study.
All three genetic approaches
can be used to help find the genes causing HCM in the different cat breeds.
Investigators will continue the "Candidate Gene Approach", only a few
samples are required for these types of studies. But, for an Association or
Family Study, many samples and breeder cooperation is required. DNA samples must
be collected from affected and normal cats and relatives for the Family
Studies. The heart condition of each cat must be confirmed by health records.
Our laboratory will assist cat breeders who want to eliminate heart disease
from their breeds. We will help develop a sample and record database for the
future study of heart disease in cats. Breeders can participate if they have
identified isolated cases of heart disease for an Association Study or they can
provide extensive family data for a Family Study.
Samples for DNA isolation can be
collected in a variety of ways:
1) If a cat has been diagnosed with heart disease and is alive, a blood
sample can be collected and sent to the laboratory along with records on the
cat.
2) If HCM was detected after
sudden death, the heart needs to be saved in formalin and the spleen and/or
kidney must be IMMEDIATELY removed from the cat and frozen until shipment to
the laboratory. Health records also need to be sent with the samples. These
samples should also be collected if a cat with known heart disease succumbs tot
he disease or is euthanized.
3) If a cat is normal but is
a direct relative of a cat with heart disease, a blood sample can be collected
and stored in the database. These samples should be collected when a breeder can
collect samples from many relatives and can continue monitoring of most related
cats for heart disease.
From Dr. Lyons at UC Davis http://faculty.vetmed.ucdavis.edu/Faculty/lalyons/Sites/heart.htm
