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L-2-HGA (L-2-hydroxyglutaric aciduria)
in Staffordshire Bull Terriers is a neurometabolic disorder
characterised by elevated levels of L-2-hydroxyglutaric acid in
urine, plasma and cerebrospinal fluid.
L-2-HGA affects the central nervous
system, with clinical signs usually apparent between 6 months and
one year (although they can appear later). Symptoms include
epileptic seizures, "wobbly" gait, tremors, muscle stiffness as a
result of exercise or excitement and altered behaviour.
The mutation, or change to the
structure of the gene, probably occurred spontaneously in a single
dog but once in the population has been inherited from generation to
generation like any other gene. The disorder shows an autosomal
recessive mode of inheritance: two copies of the defective gene (one
inherited from each parent) have to be present for a dog to be
affected by the disease. Individuals with one copy of the defective
gene and one copy of the normal gene - called carriers - show no
symptoms but can pass the defective gene onto their offspring. When
two apparently healthy carriers are crossed, 25% (on average) of the
offspring will be affected by the disease, 25% will be clear and the
remaining 50% will themselves be carriers
The mutation responsible for the
disease has recently been identified at the Animal Health Trust.
Using the information from this research, we have developed a DNA
test for the disease. This test not only diagnoses dogs affected
with this disease but can also detect those dogs which are carriers,
displaying no symptoms of the disease but able to produce affected
pups. Carriers could not be detected by the tests previously
available which involved either a blood or urine test detecting
elevated levels of L-2-hydroxyglutarate or magnetic resonance
imaging. Under most circumstances, there will be a much greater
number of carriers than affected animals in a population. It is
important to eliminate such carriers from a breeding population
since they represent a hidden reservoir of the disease that can
produce affected dogs at any time.
TEST NOW
AVAILABLE IN AUSTRALIA - Please contact
GENETIC TECHNOLOGY
Cheek swabs can be
taken by a Vet or an Authorised Collector for Genetics Technology. A
list of names can be found on their web site for each state.
Breeders will be sent results
identifying their dog as belonging to one of three categories:
CLEAR: the dog has 2 copies of the
normal gene and will neither develop L-2-HGA, nor pass a copy of
the L-2-HGA gene to any of its offspring.
CARRIER: the dog has one copy of
the normal gene and one copy of the mutant gene that causes
L-2-HGA. It will not develop L-2-HGA but will pass on the L-2-HGA
gene to 50% (on average) of its offspring.
AFFECTED: the dog has two copies
of the L-2-HGA mutation and is affected with L-2-HGA. It will
develop L-2-HGA at some stage during its lifetime, assuming it
lives to an appropriate age.
Carriers can still be bred to clear
dogs. On average, 50% of such a litter will be clear and 50%
carriers; there can be no affected produced from such a mating.
Pups which will be used for breeding can themselves be DNA tested to
determine whether they are clear or carrier.
HC - Hereditary Cataracts (also called
Juvenile Cataracts)
Hereditary
Cataract in Staffordshire Bull Terriers has been recognized as an
inherited condition since the late 1970’s. Affected dogs develop
cataracts in both eyes at an early age. The condition is not
congenital, so the lenses are normal at birth but cataracts appear
at a few weeks to months in age, progressing to total cataract (and
resulting blindness) by 2 to 3 years of age. The mutation, or change
to the structure of the gene, probably occurred spontaneously in a
single dog but once in the population has been inherited from
generation to generation like any other gene. The disorder shows an
autosomal recessive mode of inheritance: two copies of the defective
gene (one inherited from each parent) have to be present for a dog
to be affected by the disease. Individuals with one copy of the
defective gene and one copy of the normal gene - called carriers -
show no symptoms but can pass the defective gene onto their
offspring. When two apparently healthy carriers are crossed, 25% (on
average) of the offspring will be affected by the disease, 25% will
be clear and the remaining 50% will themselves be carriers. The
mutation responsible for the disease has recently been identified at
the Animal Health Trust. Using the information from this research,
we have developed a DNA test for the disease. This test not only
diagnoses dogs affected with the disease but can also detect those
dogs which are carriers, displaying no symptoms of the disease but
able to produce affected pups. Under most circumstances, there will
be a much greater number of carriers than affected animals in a
population. It is important to eliminate such carriers from a
breeding population since they represent a hidden reservoir of the
disease that can produce affected dogs at any time.
TEST NOW
AVAILABLE IN AUSTRALIA - Please contact
GENETIC TECHNOLOGY
Cheek swabs can be
taken by a Vet or an Authorised Collector for Genetics Technology. A
list of names can be found on their web site for each state.
Breeders will be sent results identifying their dog as belonging to
one of three categories:
CLEAR: the
dog has 2 copies of the normal gene and will neither develop
Hereditary Cataract, nor pass a copy of the Hereditary Cataract gene
to any of its offspring.
CARRIER:
the dog has one copy of the normal gene and one copy of the mutant
gene that causes Hereditary Cataract. It will not develop Hereditary
Cataract but will pass on the Hereditary Cataract gene to 50% (on
average) of its offspring.
AFFECTED:
the dog has two copies of the Hereditary Cataract mutation and is
affected with Hereditary Cataract. It will develop Hereditary
Cataract at some stage during its lifetime, assuming it lives to an
appropriate age.
Carriers
can still be bred to clear dogs. On average, 50% of such a litter
will be clear and 50% carriers; there can be no affecteds produced
from such a mating. Pups which will be used for breeding can
themselves be DNA tested to determine whether they are clear or
carrier.
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