Health and Genetics of Border Collies -
A Breeder and Buyer's Guide 2002
The
Border Collie stands alone in its exceptional ability
to work livestock. ABCA defines the breed by this working ability. The
main goal of any Border Collie breeder should be to
produce sound, useful, working dogs. While Border Collies also excel in many
non-herding activities, they should be bred primarily to work livestock. The
ultimate responsibility for maintaining the integrity of this as yet unspoiled
breed lies with the breeders. Breeders are urged to take this responsibility
seriously. Puppy buyers are encouraged to buy only from those breeders who do
take this responsibility seriously.
Both
breeders and buyers should understand there are risks involved in any breeding,
regardless of the amount of care taken to avoid problems. In order to ensure a
healthy gene pool for future generations of Border Collies, breeding prospects
should be evaluated with reasonable concern for potential problems and
realistic goals for what will be produced. The breeding prospect should be
considered as a whole being, with positive and negative aspects of the
individual being weighed and balanced for an overall picture of a dog's
suitability. Breeding should be undertaken with thoughts of what the parents
have to offer to their pups that could benefit the breed.
Genetic
Diseases
To be
considered a genetic disease, a health problem needs to have been demonstrated
to be heritable, that is, passed on through one or both parents. Some diseases
have high heritability, which means if the genes are present, the individual
will have the disease, and some diseases have low heritability, meaning both
genetic and environmental factors are involved in whether the disease occurs.
It is generally easier to control diseases with high heritability because all
individuals with the genetic makeup for the disease can usually be identified.
The term heritable disease should be distinguished from the term congenital
disease, or problems that are present from birth,
which may or may not be heritable.
Border
Collies are considered to be a generally healthy breed. However, as in all
animals, there are some potential health problems. This information is
presented to help both breeders and buyers to become more aware of some of the
health and genetic issues in the breed at this time.
The
primary genetic diseases currently thought to be a problem in the breed are as
follows:
Hip Dysplasia (HD) HD is by far the most prevalent known genetic disease that affects
Border Collies. Factors that contribute to the development of HD ultimately
cause the hip joint to be damaged. Joint damage called osteoarthritis, also
known as degenerative joint disease (DJD) is manifested by cartilage and bone
breakdown and irregular bony remodeling in response
to stresses and inflammatory processes in the joint. DJD is, in effect, the
identifiable result of factors that cause HD. The standard for diagnosing HD at
this time is still the front extended-leg view of the hips on x-ray such as
that evaluated by The Orthopedic Foundation for
Animals (OFA). OFA reports a 12.6% affected rate for Border Collies evaluated
from 1974-2000. This HD incidence ranks them somewhere in the middle of the dog
breeds. Pre-submission screening and selection for probable favorable
OFA results by owners and their veterinarians very likely skews this percentage
significantly to the low side. Therefore, the true incidence of HD is probably
much higher, possibly as high as double the OFA
figure. If true, this would mean, on average, one out of every four Border
Collies has HD.
Despite
what some may claim, data from numerous scientific studies provide overwhelming
evidence that HD is an inherited disease. It is
thought to be caused by at least three and possibly as many as six primary
genes. The number of genes involved, combined with the high incidence, means
it's probable that most Border Collies are at least carriers of one or more of
the genes that can contribute to the development of HD, even if they don't have
the disease themselves. To confuse matters more, the expression of the disease
is affected by environmental conditions such as the type and amount of food a dog
gets at critical growth stages, as well as the type and amount of exercise and
activity it gets. It must be remembered, however, that these environmental
factors do not cause HD. They merely affect whether the HD genes present in
that individual will be expressed to the fullest. Even if the expression of HD
in a certain individual is suppressed by careful control of environmental
factors, you have not changed the dog's genetic makeup. That dog will still
pass on the genetic tendency for HD just as if it actually had the disease.
Conversely, if a dog does not have the genes for HD, it won't develop the
disease no matter how it's raised.
The
possible incidence of one in four dogs may seem falsely high if the presence of
HD is defined by dogs showing significant lameness. The clinical symptoms
of HD do not always correlate well with the severity of the disease as judged
by radiological findings. Border Collies with HD that are
fortunate enough to show few if any symptoms may have progeny that are not so fortunate.
The exact complex combination of genetic and environmental factors that
contributed to an individual's lack of symptoms will not occur in its
pups. Therefore, it is important to remember that a high tolerance of an
individual for the effects of HD does not mean that individual is suitable as a
breeding prospect.
The
best way, at this time, to avoid producing puppies with a predisposition to
develop HD is to test both parents and be aware of the hip status of other
related dogs such as the parents' other progeny, the parents' parents, and the
littermates and half siblings of the parents. The more tested, unaffected dogs
there are in the pedigrees, the better the chances of producing unaffected
pups. Unfortunately, even following the most stringent guidelines, puppies may
still be produced that will develop HD. This does not mean there's no point in
testing parents before breeding them. This line of false reasoning is akin to arguing that,
because working parents will occasionally produce pups that won't work, there's
no point in testing the working ability of breeding stock.
Selection for good hips will increase your chances of producing pups with good
hips, but it's unrealistic to expect that puppies with HD will never be
produced from tested, unaffected parents. Likewise, it is unrealistic to expect
every dog who has ever produced a pup with HD to be
banned from breeding. Since it's likely that most non HD-affected Border
Collies are carriers of one or more of the genes for HD, most dogs will produce
at least one pup with HD if bred enough times. Sooner or later, a cross with
another carrier will produce the wrong combination of the HD genes and an
affected pup will result.
Given
the incidence and complexities involved with HD in our breed, the
recommendations at this time are to breed only hip tested, unaffected
parents. Also, try to plan crosses having as many tested,
unaffected dogs in the pedigrees of both parents as possible. If an affected
puppy is produced from a cross of two unaffected parents, at the very least,
don't repeat that particular cross because that affected puppy has
proven that the two parents can together provide the right combinations of
genes to create more puppies with HD.
The
ABCA Health and Genetics Committee is investigating a
promising new technique that measures several factors involved in the
development of HD. This procedure involves taking hip x-rays on a sedated dog
while the dog is in a kneeling position. This angle is favorable
for identifying strengths and weaknesses in the hip joint in a more natural,
weight-bearing position. This type of measurement is called a Dorsolateral Subluxation (DLS)
measurement. ABCA is planning a study to evaluate this technique in 8-12 month
old Border Collies.
Diagram of the position for
x-ray in the DLS procedure
Collie
Eye Anomaly (CEA)
CEA is a congenital disorder where the parts of the eye, particularly the
retinal area, do not develop normally. The severity of the disease ranges from
no visual impairment to blindness. It is not a progressive disease and affected
dogs normally only have mildly impaired vision. Puppies should be tested before
12 weeks of age, if possible, by a Diplomate of the
Association of Canine Veterinary Ophthalmologists (DACVO) because some dogs
have a mild form of the disease called "go normal", where normal tissue
grows over and covers up the diseased area as the dog matures. Identification
of "go normals" is important, as these dogs
are affected with CEA and will produce affected puppies just as if they had
full blown expression of the disease.
This
disease is much more straightforward than HD in both its inheritance patterns
and in our ability to control it. CEA is an autosomal
recessive disorder. Autosomal means it is passed on
and expressed equally in males or females. Recessive means a dog may carry a
bad CEA gene and pass it on to its offspring without having the disease itself.
A dog is defined as Clear if it has no bad CEA genes. A dog is defined as a
Carrier if it has one bad CEA gene and one normal gene. Both the Carrier and
the Clear dogs will be unaffected and will test negative for CEA in the eye
exam. A dog is defined as Affected if it eye tests positive for CEA. The
outcomes of the different crosses of these dogs are as follows:
|
Clear
X Clear = 100% CEA Clear puppies Clear
X Carrier = on average, 50% Clear, 50% Carriers Clear
X Affected = 100% Carriers Carrier
X Carrier = on average, 25% Clear, 50% Carriers, 25% Affected Carrier
X Affected = on average, 50% Affected, 50% Carriers Affected
X Affected = 100% Affected |
The
incidence of CEA in Border Collies in
The
ABCA, with support from other working Border Collie
groups and owners, has funded Dr Gregory Acland from
the James A. Baker Institute for Animal Health,
v
For owners of known Carriers (unaffected dogs that have produced a
CEA affected puppy) - ABCA recommends that anyone who inquires about the dog's
progeny or as a mate be told that it is a Carrier. It also recommends that people
who have any of this dog's progeny be informed that all its offspring have at
least a 50% chance of also being a Carrier even if the other parent is neither
a Carrier nor Affected.
v
For breeders of a litter in which one parent is a known Carrier -
The ABCA recommends that all puppies in the litter have an ophthalmic
examination by a DACVO by 12 weeks for accurate detection of "go
normal" CEA. If this examination cannot be done, it is recommended that
the puppy buyers be informed that they must determine from an ophthalmic
examination that the dog is not affected with CEA before it is considered for
breeding, as the progeny of affected dogs are not eligible for registration.
v
Do not breed two known Carriers together, as this will likely
result in Affected puppies.
v
Do not breed CEA affected dogs. These dogs and their progeny are
not eligible for registration with ABCA at this time.
Epilepsy Epilepsy
is a disease characterized by seizures or "fits" as they are
sometimes called. Although it's clear Border Collies can be affected with
epilepsy, the incidence and heritability in our breed are unknown. The ABCA is
conducting a health survey to determine the extent of this problem in the
breed. Please help us in this effort, whether you have an affected dog or not,
by responding to the health survey on ABCA's web page
listed below.
Since
there can be many causes, determining why a dog has seizures is a complex
process. The diagnosis of primary epilepsy is made based on negative results
for other causes of seizures. Therefore, it is a diagnosis made by exclusion
rather than by a specific test. Since we have little breed-specific information
to go on, ABCA breeding recommendations concerning this disease are based on
those for other affected breeds in which the disease is more well-defined.
Recommendations are: Do not breed affected dogs. If two unaffected dogs
produce an affected puppy, do not repeat that cross.
Genetic diseases not considered to be a significant problem in the
breed at this time:
Progressive
Retinal Atrophy
(PRA) PRA is a progressive disease where tissue in the retina of the eye is
destroyed. It may initially be noticed as decreased ability of the dog to see
at night, and may eventually progress to total blindness.
Despite
the persisting impression that this genetic disease is prevalent in the breed,
extensive investigation has shown the incidence of PRA in Border Collies in
Elbow
dysplasia Elbow dysplasia is a general term used
for what is essentially three different types of
degenerative elbow disease. These diseases may occur singly or together and are
thought to be caused by several different genes.
More
and more owners are having their Border Collies' elbows evaluated each year.
However, OFA reports a 0% incidence of elbow dysplasia
for 210 Border Collies tested from January 1974-December 1999. ABCA does not
consider elbow dysplasia a significant health problem
in the breed at this time.
Common diseases with questionable heritable cause:
Osteochondritis Dissecans (OCD) OCD is a condition that
occurs primarily in puppies between the ages of 4-9 months, but can also be
found in older puppies. It is considered to be a common disease in rapidly
growing dogs of large breeds. However, medium breeds such as the Border Collie can also have a high incidence of this disease. It is
seen twice as often in males as in females. The shoulder joint is the most
commonly affected site but it can be seen in stifles, elbows, hocks or other
joints. The diagnosis is usually confirmed by x-ray of the involved
joints. In approximately one third of the cases of OCD, the disease is
bilateral (in both joints). Occasionally, it is present in several different
joints in the same individual. OCD is thought to be caused by a problem in the
growth rate of the joint cartilage relative to the underlying subchondral bone.
Although
the factors that cause OCD are not completely understood, direct factors
considered to be involved in the development of OCD are rapid growth and trauma
to the joint. Indirect factors affecting rapid growth include nutrition,
hormones, and genetic predisposition to rapid growth and large size. Indirect
influences that may lead to increased trauma to the joint include conformation
and behavior, which are also influenced by heredity.
Therefore, the genetic link for most types of OCD is considered to be indirect,
that is, an inherited tendency. Certain sites for OCD lesions, such as the
elbow, appear to have a greater direct genetic contribution and a higher
heritability than other sites, such as the shoulder. The most important
contributing factor in OCD of the shoulder, the most common site, is thought to
be trauma. OCD can best be prevented in growing puppies by controlling the main
precipitating factors, overnutrition and activities
that could result in injury to the joints.
Because
factors involved in the heritability of OCD are considered to be indirect, and
therefore not easily controlled by selection, ABCA has no breeding
recommendations for OCD at this time.
Common diseases with no known heritable contribution:
Focal/Multifocal Acquired Retinopathy (FMAR): This inflammatory eye disease
is common in many working breeds and is probably the most frequently seen
retinal lesion in Border Collies. Sometimes called "distemper scars"
or "worm scars", it is characterized by lesions in the retina that
can accumulate over the years, often leading to impaired vision and sometimes
leading to blindness. The lesions have a typical "bull's eye"
pattern, and tend to be asymmetrical (affect one eye more than the
other). The age of onset and rate of progression varies greatly from
individual to individual. Males are more frequently affected than
females. The characteristics of this disease strongly suggest
environmental cause; no heritable pattern has ever been established for its
occurrence. Its pathology clearly distinguishes it from
PRA, although it is sometimes mistaken for PRA, especially in the later
stages of the disease.
In
summary, this
brochure is meant to provide a brief description of some common diseases, some
current knowledge about their heritability in our breed, and relevant breeding
recommendations. Please remember, diseases present in Border Collies are not
limited to those discussed here. Also remember, these recommendations are
guidelines, not restrictions. Keep track of updated and more in depth
Border Collie health and genetics information by checking the ABCA web site at www.americanbordercollie.org .
Copyright © American Border Collie
Association. All rights reserved.
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