Some Inherited Disorders in Labradors
Most purebred dogs, including Labrador Retrievers, are
occasionally born with
an inherited disorder. The more common genetic disorders
include hip dysplasia, elbow dysplasia, retinal dysplasia, and
PRA. Epilepsy,
heart defects, canine hypothyroidism, and bleeding
disorders are rarely seen in Labradors. Some disorders, including hip dysplasia, elbow dysplasia, seizures, heart defects, and some bleeding disorders, can be the result of non-genetic factors.
EIC (Exercise Induced Collapse)
EIC is an inherited disorder in Labradors. The gene responsible for this disorder is recessive, therefore, only dogs that inherit a defective gene from both parents will develop EIC. Carriers with one normal gene and one abnormal gene will not develop this disorder. Dogs with 2 abnormal genes may experience EIC episodes. These dogs may collapse following physical activity (more often in hot weather). They usually recover with rest, but the condition is sometime fatal. Once diagnosed, careful monitoring of the dogs exercise intensity may prevent future episodes.
Reducing the risk of genetic disorders in Labradors: There is a genetic test available, and this disorder can be prevented. EIC-normal dogs bred to EIC-carriers will not produce any affected puppies. Approximately 25% of the puppies from the breeding of 2 EIC-carriets will be affected. An EIC-normal dog bred to an EIC-affected dog will not produce any affected puppies. All the puppies from 2 EIC-affected dogs will have this disorder.
Eye Disorders
There are several
minor inherited disorders associated with eyelids. The eyelashes
are turned inward in
Entropion. In Ectropion, the eyelashes are turned outward.
Distichiasis is associated with extra eyelashes. Most of the
conditions are
easily corrected with minor surgery.
More serious inherited eye disorders in Labradors include
cataracts,
Retinal Dysplasia, and Progressive Retinal Atrophy (PRA). Not all
eye diseases result in
blindness. Surgery is a possible treatment for
cataracts.
Reducing the risk of genetic disorders in Labradors:
Annual eye examinations by
certified veterinary ophthalmologists are recommended since some eye
disorders are not detected in young dogs. There is a genetic test available for prcd- PRA (progressive rod-cone degeneration PRA). The gene that is associated with this disorder is a recessive trait. As long as one parent has 2 normal genes, none of the offspring will develop prcd-PRA. Generally, affected dogs should not be bred. However, dog affected with prcd-PRA can be bred to a dog with 2 normal genes, and all the offspring will be unaffected carriers with one normal gene and one defective gene.
Hip and Elbow Dysplasia
Hip and elbow dysplasia affects many breeds. Hip
dysplasia is associated with a deterioration of the ball and socket hip
joint. The dog experiences pain and progressive lameness.
The severity of the condition ranges from slight to severe.
Surgical repair is often very successful. Elbow dysplasia
also occurs in Labradors and a surgical repair may be an option for
affected dogs. Factors other than genes are associated with
dysplasia in joints. Nutrition, excessive joint stress
and extra weight at a young age contribute to hip and elbow dysplasia.
Reducing the risk of these genetic disorders in Labradors:
Orthopedic Foundation for Animals (OFA) certifies hip structure based
on x-ray evaluation. OFA certifies hips as excellent,
good and fair. PennHIP evaluates hips based on
hip laxity. Dogs that score 50% or better are potential
candidates for
breeding. Affected dogs should be excluded from their breeding
program.
OFA also certifies elbows. Since inherited elbow diseases
are usually detected in affected dogs at a young age, some established
"old
school" breeders do not have elbow x-rays taken if the dog has not been
lame. Most responsible breeders obtain elbow clearance.
Affected dogs should not be
bred.
Seizure disorders and epilepsy
Seizures in Labradors can be
due to an inherited form of epilepsy. Seizures are often a result
of a wide variety of non-genetic factors.
Infections, trauma, low blood sugar levels, toxins and pesticides
exposure can result in seizures. This disorder is very difficult
for dog owners to cope with. Fortunately, this
disorder is rare and many dogs respond well to medication.
Reducing the risk of this genetic disorder in Labradors:
There is no screening test for the inherited form of epilepsy.
Affected dogs should not be bred. Dogs with several close
relatives with a seizure disorder may not be good candidates for
breeding.
Thyroid Disease
Canine hypothyroidism is due to a deficiency of the hormones
produced by the
thyroid gland. Autoimmune lymphocytic thyroiditis is an inherited
form of
hypothyroidism that very rarely occurs in Labradors. Symptoms of
the
disorder include weight gain, lethargy and hair loss. The
disorder usually
develops by the time the dogs is 5 years old. It is easily
treated with a
daily dose of thyroxin. This inherited form of hypothyroidism is
very rare in Labradors.
Reducing the risk of this genetic disorder in Labradors:
OFA offers a thyroid registry, but this clearance is
not
recommended for Labradors. Dogs with close relatives should be screened. Affected dogs should not be
breed.
Tricuspid Valve Dyslasia
Tricuspid
Valve Dysplasia, or TVD, is a congenital defect that is rarely seen
in
Labradors. During embryonic development, the flaps of the
tricuspic valve adhered to the wall of the heart. Normally, these
flaps detach and a functional valve between the
chambers of the right side of the heart develops. The valve opens
to allow the flow of blood from the atrium into the ventricle.
The closed valve prevents blood from flowing back into the atrium when
the ventricle pumps blood out to the heart. If the flaps
remain attached, the valve does not develop properly. The result
is an abnormal flow of blood in the right side of the heart.
TVD is known to be an inherited disorder. Research conducted by
Dr. Kathy Wright suggests that TVD is caused by a dominant gene with
reduced penetrance. Some dogs
with the defect gene may not develop TVD, but
they can pass the defect gene to their offspring. The severity of the
disorder varies from very mild to very severe. Some dogs with TVD
develop fatal cardiac changes.
Reducing the risk of these genetic disorders in Labradors:
OFA issues a
cardiac certification for dogs that are not affected. An
echocardiagram is recommended to rule out TVD since heart murmurs are
not detected in some dogs with a mild form of the disorder.
Although this clearance is not
yet
recommended for Labradors, some breeders have started to screen their
breeding stock. Affected dogs should not be bred. Dogs
with several close relatives with TVD may not be good candidates
for breeding.
Von Willebrand's Disease
Von Willebrand's Disease is an inherited bleeding disorder
that is
rare in Labradors. A recessive gene that codes for an abnormal
protein is
responsible of this disease. The severity of the disorder is
variable.
Reducing the risk of this genetic disorder in Labradors:
A screening tests for this
bleeding disorder is available,
but the occurrence of this bleeding disorder is Labradors is very
low. Currently, screening
for this disorder is not recommended for Labradors. Dogs with affected relatives should be screened. Affected dogs
are not candidates for breeding.