Over the years there has been a shift in the profile of diseases
seen by veterinarians. Improvements and developments of antibiotics
and more effective vaccines have controlled many of the infectious
diseases that caused problems in the past.
As the frequency of these infectious diseases has declined, there
has been a relative increase in diseases that have a genetic basis.
Inherited diseases result from mutations or changes to one or
more genes that make up the canine genome. There are two kinds
of gene mutation that can occur: a dominant and a recessive mutation.
In simple dominant diseases, affected offspring inherit just one
copy of the mutant gene from either the father or mother. In simple
recessive diseases, affected offspring have 2 copies of the recessive
mutation, one inherited from the father and one inherited from
the mother. Offspring that have one recessive mutant gene and
one normal version of the gene are termed carriers; such individuals
will not be clinically affected by the condition that results
from the recessive mutation. However, a carrier will pass on the
recessive mutant gene to approximately 50% of its offspring, the
other 50% receiving the normal version of the gene.
Some inherited diseases are however more genetically complex resulting
from mutations of more than one gene. These are called polygenic
inherited diseases such as hip and elbow dysplasia, epilepsy,
and inherited cardiac disease and cancer.
However, the vast majority of canine diseases are a result of
recessive mutations in specific genes.
Around 400 inherited diseases have been recognised in the canine
population most of which have a human equivalent. This interests
the scientists because it has been realised that 75% of the genes
that are in humans also appear to be in dogs. Pedigree dog breeds
are essentially like closed human populations and, therefore,
research in finding gene mutations in dogs also helps research
in human conditions.
Over the past few years, canine molecular biologists have laid
the foundations for a whole new era of informed dog breeding.
The recently published map of the canine genome together with
its component markers provides an invaluable resource to start
addressing inherited diseases in dogs. The vast majority of canine
diseases are a result of recessive mutations in specific genes.
The availability of the map greatly facilitates that search for
the genes that cause inherited disease. Once disease genes have
been identified, relatively simple DNA (Deoxyribonucleic Acid)
based tests can be developed to identify the presence of a mutant,
diseased gene in a DNA sample.
The availability of such tests will provide for the first time,
a method of identifying carriers of recessive mutant genes.
Breeding Programmes
Being able to identify carriers will have an immense impact on
breeding programmes. The removal of carriers from the breeding
stock is not always the ideal solution because although you are
minimising the spread of the mutant gene, you may also be removing
positive qualities that the breed requires in order to maintain
its overall health; in other words, you could be throwing the
baby out with the bath water. The availability of a DNA test allows
much more subtle manipulation of breeding programmes to reduce
the frequency of a particular mutation whilst retaining some of
the positive features present in affected lines
If a bitch is identified as a carrier using a DNA test, rather
than removing this bitch from the breed's gene pool, potential
mates can be screened to identify that they are clear. If a clear
dog and a carrier bitch are mated approximately half of the offspring
will be carriers and the other half will be totally clear of the
disease gene, so there will be no clinically affected puppies
in the litter. The litter can then be DNA tested with a cheek
swab at about four to five weeks of age to show which of them
are carriers and which of them are genetically clear puppies.
Once identified, the genetically clear puppies can be bred from
in the future, thereby removing the mutant gene from the breeding
population, but at the same time retaining the many positive features
the line has to offer.
The availability of a DNA test also means that under some circumstances
genetically affected dogs can be bred from. If an affected dog
is mated to a DNA tested clear mate all the offspring will be
carriers but not clinically affected in any way. If one of these
carrier progeny is subsequently mated to another clear mate, then
approximately half this second generation will be clear and will
be identifiable by DNA testing. Thus a breeder can go from an
affected dog to a clear dog in just 2 generations using a DNA
test driven selection process.
There are now about 50 DNA tests available for different conditions
and for different breeds. The majority of these have been developed
in the USA.
OES DNA PROJECTS in America
Information from Ann Lapp, OESCA Health And Research Committee, Chairperson.
The Old English Sheepdog Club Of America is supporting research
through The American Kennel Clubs Canine Health Foundation in
two major areas.
1. The Genetics of Cerebellar Degeneration. Dr Natasha Olby, North
Carolina State University.
Old English Sheepdogs are affected with hereditary cerebellar
degeneration (abiotrophy). The condition causes ataxia (inco-ordination)
which begins late in life and is inherited as a recessive trait.
While not necessarily fatal ataxia results in frequent falls and
injury and seriously comprises the dog's quality of life. The
delayed onset and recessive inheritance of this disease means
that the trait can be widespread in the population and difficult
to eliminate without a DNA test for carriers.
Through the efforts of OESCA, over 350 blood samples and numerous
tissue samples from OES continue to provide essential data for
Cerebella Ataxia (CA) research. There is still a critical need
for blood and tissue samples from affected dogs and from relatives
of affected dogs. OES breeders and owners, or the veterinarian
of the owners wishing to provide samples should be instructed
to make direct contact with Dr Olby. (Note. Dr Olby is a Cambridge
University UK graduate)
2. Investigation of Candidate Loci For Progressive Retinal
Atrophy, Dr Simon
Peterson-Jones, Michigan State University.
Progressive retinal atrophy (PRA) is a common cause of blindness
in purebred dogs. It is an inherited disease and there are several
different forms resulting from defects in different genes. Most
forms are due to a defect in a single gene and are inherited in
an autosomal recessive manner. PRA has become a problem in OES
and Papillon breeds. In both these breeds, dogs develop the disease
in middle age and slowly and progressively lose vision. A number
of different genes have been identified as the cause of PRA and
these are being researched in the OES and Papillon. A DNA test
will then allow breeders to identify carriers of the disease and
this will prove very valuable in eradicating PRA from their breed.
If someone has a dog with PRA or a closely related dog (immediate
family such as parents, siblings & offspring) contact Dr Simon
Peterson-Jones to be included in the study
Both researchers work directly with OESCA members and their animals
when needed. Research is progressing on schedule with expectations
that results will be forthcoming.
If someone outside of the USA would like to make a financial contribution
to either of these health studies, you may do so through OESCA
Health and Research, contact Ann Lapp Pettiboneoes@aol.com or
phone 715-878-4861
The next possible areas of OESCA supported research will probably be directed to cancer research or autoimmune research.
What is happening in the UK.
In Great Britain, the British Veterinary Association has operated
a hereditary eye disease-screening programme for over 30 years.
OES are listed as suffering from 3 types of Hereditary Cataract.
The checks are voluntary but conscientious breeders do this with
their breeding stock. The results are published in the Kennel
Club's quarterly issue of the Breed Records Supplement along with
litter registrations and hip scoring results.
The dogs, which are eye-screened, are either affected or clear
but with recessive genes we have no way of knowing which dogs
are the carriers until affected offspring are produced. We are
now seeing failures in the OES results and hearing of more dogs
being affected and of puppies failing litter screening.
The OES Breed Council was made aware of worsening eye problems
in the breed in April 2003.
In January 2004, I wrote an article in the Greater London OES
Club's magazine "Yours Faithfully" no 41 about recessive
genes and hereditary eye disease to try and educate and inform
the readers of the possible dangerous situation. Close breeding
and a shrinking gene pool could cause the problem of hereditary
cataract to become much worse in the next few generations.
The Kennel Club in its remit to promote the health and welfare
of pedigree dogs is embracing the new DNA technology and through
The KC Health Foundation will provide top up funding for research
projects leading to the development of DNA tests. In the last
2 years, the KC has granted £500.000 funding for research.
This included money for the Animal Health Trust's research into
Hereditary Cataract in the Staffordshire Bull Terrier and American
Cocker Spaniel.
The OES Health committee commenced fundraising to try and further
the research for a DNA test to be developed. The OES Breed Council,
held a Seminar on Sunday 23rd October 2005 at which Dr Jeff Samson,
the Kennel Club's Genetics Co-ordinator gave a talk on DNA testing
for Hereditary Diseases in Dogs and answered many questions.
The OES Health committee has already spoken to Dr Cathryn Mellersh
of The Animal Health Trust and she has agreed to take on our plight.
There is also the possibility of researching one other condition
at the same time which has yet to be decided. The Animal Health
Trust requires a blood sample, a copy pedigree and any other health
certificates i.e. Eye Test and Hip Score and any other test relevant
to your OES. Send these in confidence to the address on the AHT
form which can be printed from the Breed Councils website, www.oesbreedcouncil.org.uk
Dr C Mellersh is pleased to receive the blood samples now and
will store them until there are enough to start the research.
Groups of possibly10 related dogs make a good family gathering.
Urgently required are 20 affected animals. We need at least 100
blood samples for an effective outcome.
If anyone in Europe can help with this research by submitting
blood samples and the pedigree information you will be helping
your beloved breed to be more healthy and when a DNA Test is available
it will benefit the OES Breed worldwide as will the American DNA
research which is currently being undertaken.
The OES Health committee has written to all the UK OES Breed
Clubs to help with fundraising efforts and donating money towards
this research. The Breed Council's website will monitor the fundraising
efforts.
We have this opportunity now to embrace this new scientific technology
for the benefit of the whole breed the world over. The Kennel
Club is offering to help with the funding and as more research
projects get off the ground, the research is going to be quicker
and cheaper.
If Breed Clubs, whether in the UK or in the countries of Europe, America or Australasia contributed towards this cause, together with donations from exhibitors, breeders and pet owners of Old English Sheepdogs, the money raised would result in a DNA test being available for future generations of healthy OES.
What a wonderful legacy this would be to the breed from the present day OES enthusiasts who hold the breed in trust for the future generations of Old English Sheepdog lovers to come.
Helen Harris
July 2005
For further information or questions please contact Helen Harris.
Tel 020 8776 1437
Email helen.harris8@ntlworld.com
or Mr Ray Owen. Email owen@amblegait.freeserve.co.uk
Donations should be made payable to "OES Health." And
sent to:-
The Treasurer of the Old English Sheepdog breed council.
Mrs G Bigger.
61 Woodlands Drive Offerton, Stockport, Cheshire SK2 5AP
The information for this article has been compiled with the help from reliable sources on the Internet, The Animal Health Trust, The Kennel Club Website www.the-kennel-club.org.uk and the Dog Press.