The Mainland Staffordshire Bull Terrier Society

GENETIC CONDITIONS

Can be screened for by DNA testing

 

1. L-2-HYDROXYGLUTARIC ACIDURIA – (L-2-HGA)

L-2-HGA is a debilitating disease that affects many breeds, including Staffordshire Bull Terriers.  It is a neurometabolic disorder that is inherited from a dog’s parents and caused by a failure to break down L-2-HGA acid. Raised levels of L-2-HGA acid are found in urine, plasma and cerebrospinal fluid.

L-2-HGA is passed on by dogs who are a carrier of the genetic mutation.

For dogs affected by L-2-HGA, their life is usually short. Some may live into their teens, but most pass away or are euthanized between 6 months and 2 years due to severe symptoms, especially fits.

 

What are the signs and/or symptoms?

L-2-HGA causes a variety of signs and/or symptoms, not all appear in every dog.

Signs may start between 6 and 12 months of age, although some dogs may start showing signs shortly after birth.

Some of the common signs are:

• seizures ('fits', 'epilepsy');
• ataxia (wobbly walking);
• dementia and other behavioural changes;
• tremors and cramps, especially of back legs; and/or
• other signs reported include loss of obedience training, disorientation

These signs may start suddenly or gradually.

 

By testing both male and female dogs before breeding, the breeder and future puppy owner can be sure that the pups are ‘hereditarily clear’ – this mean that the male and female do not have the mutation themselves, therefore will not pass it onto their offspring. If only one parent or neither parents are tested, potentially to save money, even without showing signs or symptoms themselves, the pups could be carriers, and never show symptoms, but will pass on the mutation. Worse case scenario, the pups could be affected by this debilitating disease.

 

So, what do the DNA results mean?

• 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. Carriers can still be bred to clear dogs. On average, 50% of such a litter will be clear and 50% carriers.
• 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.

 

Reference Source: http://www.l2hga.com/

 

2. HEREDITARY CATARACTS – (HC)

Hereditary Cataract in Staffordshire Bull Terriers has been recognised 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) must 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

Hereditary Cataracts (HC) are a clouding of the lens of the eye caused by a breakdown of tissue in the eye. This condition generally results in an inability to see clearly and can cause total blindness. In canines, cataracts are often familial; this type is known as Hereditary Cataracts. A mutation in the HSF4 gene causes this type of cataracts in several breeds of dogs. In this case, the dog is typically affected bilaterally, in that both eyes are affected by the cataracts. The cataracts associated with HSF4 also occur in the posterior region of the lens. They usually start by being small and grow progressively, though the speed of growth is highly variable. Some cataracts will grow so slowly that the dog's vision remains relatively clear, while others will grow such a way that the dog will quickly go blind. Corrective surgery is possible, though it is costly and is not always effective.

 

Genetic testing of the HSF4 gene will reliably determine whether a dog is a genetic Carrier of Hereditary cataracts. Hereditary cataracts are inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same Mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting the disease and a 50% chance of inheriting one copy and being a carrier of the HSF4 gene mutation. Reliable genetic testing is important for determining breeding practices. Because symptoms may not appear until adulthood, genetic testing should be performed before breeding. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Dogs that are not carriers of the mutation have no increased risk of having affected pups.

A DNA test for HC is available. Breeders will be sent results identifying their dog as belonging to one of three categories.

 

So, what do the DNA results mean?

• CLEAR:     The dog has two 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. 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 puppies 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.
• 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.

References:

http://www.animalgenetics.us/Canine/Genetic_Disease/HC.asp

https://www.pawprintgenetics.com/products/tests/details/119/

 

3. DEGENERATIVE MYELOPATHY (DM)

Degenerative Myelopathy is an inherited neurologic disorder caused by a genetic mutation of the SOD1 gene, known to be carried by Staffordshire Bull Terriers. The mutation is found in many breeds; however, it is still currently unclear whether a Staffordshire Bull Terrier carrying two copies of the mutation will develop the disease. The variable presentation between breeds suggests that there are environmental or other genetic factors responsible for modifying disease expression. The average age of onset for dogs with degenerative myelopathy is approximately nine years of age in many breeds however, the overall frequency and approximate age of disease onset is currently unreported in Staffordshire Bull Terriers. The disease affects the White Matter tissue of the spinal cord and is considered the canine equivalent to amyotrophic lateral sclerosis (Lou Gehrig’s disease) found in humans.

Affected dogs usually present in adulthood with gradual muscle atrophy and loss of coordination typically beginning in the hind limbs due to degeneration of the nerves.

The condition is not typically painful for the dog but will progress until the dog is no longer able to walk. The gait of dogs affected with degenerative myelopathy can be difficult to distinguish from the gait of dogs with hip dysplasia, arthritis of other joints of the hind limbs, or intervertebral disc disease. Late in the progression of disease, dogs may lose faecal and urinary continence and the forelimbs may be affected. Affected dogs may fully lose the ability to walk 6 months to 2 years after the onset of symptoms.

Reference Source: https://www.pawprintgenetics.com/products/tests/details/87/?breed=113

 

TESTING YOUR STAFFORD FOR GENETIC CONDITIONS/DISEASES

Most people consider health testing to be a visit to the vet, leaving with a clean bill of health. This is not what we are referring to when we say heath testing. We are referring to DNA Health Testing / Screening for any of a Stafford’s hereditary genetic conditions/diseases.

To have a dog DNA Health Tested, a swab will be taken, most commonly from the epithelial cells from inside the cheek of the dog either with a small brush or cotton swab. DNA health testing can also be done via blood sample.

These swabs should be collected by an approved collection method. This mean either taken by an agent for the laboratory that you have chosen to do the testing, or by ordering a kit yourself and taking your dog to your vet to do the swab.

We suggest an approved collection method as to get ‘verified’ results, you cannot swab the dog yourself. Verified means a neutral person, lab agent or vet, has sighted the dog, scanned their microchip number and signed that the swab is for the dog they have sighted, scanned and swabbed.

If you do the swab yourself, the integrity of your results will be lost.

The swab is then sent to one of the laboratories, our closest and most commonly used for Staffords are in Australia. The cost can vary from lab to lab. The results should come back within 2 to 6 weeks depending upon where you send them.

The DNA Profile (fingerprint) is a permanent identification unique to each dog can also be done at this time. The DNA profile also allows you to have further testing done for proof of parentage on puppies in the future.

 

So, what do the DNA results mean?

• Clear/Normal/Not Affected: If your results show your dog is normal/clear/not affected, or any such wording for these diseases, you will not pass those horrid life limiting diseases on if you choose to breed from your dog.
• Carrier: If your dog comes back as a carrier and you still choose to breed the dog, you can now make informed decisions as to who the mate for dog will be as they also MUST be tested and MUST be 'Clear' for the disease your dog is a carrier of. Otherwise, you may produce puppies affected by these debilitating diseases. For this reason, we do not recommend breeding from a carrier.
• Affected: If the dog comes back as affected, you are probably already having health issues and sadly your dog will most likely will be experiencing blindness or mobility issues already. These dogs must NEVER be bred from.

 

Is DNA testing really all that important?

• If your dog is a pet, and you are not looking to breed, or he/she has already been spayed/neutered then no, you do not need to look at DNA testing. Unless your pet is showing possible symptoms of the disease, in which case a DNA test is a useful tool to help diagnosis.
• If your pup came to you with copies of the certificates from your Staffords breeder for your Staffords parents that show they are clear for these diseases, then you have nothing to worry about either.

Contact Details

Leana Bartle
Chch, NZ
Email : [email protected]