Alexander Disease in Labrador Retrievers: Causes, Symptoms & Testing

The Labrador retriever is one of the UK’s most beloved and popular pedigree dog breeds, famous for its friendly nature, high intelligence, and versatility. Despite their overall robust health, like many pedigree breeds, Labradors can be affected by certain hereditary conditions that impact their wellbeing and lifespan. One such rare, yet serious condition is Alexander disease, also known as leukodystrophy.

Alexander disease (AxD) is a fatal neurodegenerative disorder affecting the nervous system of Labrador retrievers, leading to progressive impairment and paralysis, often appearing early in puppies' lives. Thankfully, advances in veterinary genetics allow responsible breeders and owners to test their dogs and take proactive steps to reduce the disease's impact on the breed.

What is Alexander disease or leukodystrophy in Labradors?

Alexander disease is a neurological disorder characterised by the degeneration of white matter in the brain due to a mutation affecting astrocyte function. The disease specifically impacts the myelin sheath—a fatty substance crucial for protecting nerve cells and facilitating proper nerve signal transmission. When myelin is lost, affected dogs develop symptoms related to impaired nerve function.

In Labradors, signs often emerge very early, between 4 to 6 weeks of age and sometimes within the first year, manifesting as tremors, muscle stiffness, loss of coordination, and progressive paralysis. Common symptoms include:

• Generalised tremors and shaking
• Muscle stiffness and spasms
• Increased spinal reflex actions
• Loss of balance and coordination
• Progressive tetraplegia (paralysis of all limbs)
• Spastic forelimbs and mild vestibular disturbances

Sadly, affected dogs deteriorate quickly, usually necessitating euthanasia to prevent suffering due to the incurable and progressive nature of the illness.

Which Labradors are at risk of Alexander disease?

Alexander disease is predominantly seen in young Labrador retrievers, often those under one year old. Both males and females can be affected equally. The condition is deeply linked to genetics; puppies who inherit the faulted gene from their parents are at risk, making pedigree and lineage critical in determining vulnerability.

Breeders with knowledge of their breeding lines’ health status can reduce risks by carefully planning matings and using available genetic testing methods to avoid producing affected litters.

How is Alexander disease inherited in Labradors?

The genetic cause of Alexander disease in Labrador retrievers traces to a missense mutation (c.719G>A) in the GFAP gene. This mutation alters an amino acid in the GFAP protein fundamental to astrocyte function, leading to neurological damage.

In Labradors, Alexander disease follows an autosomal dominant inheritance pattern, which means only one copy of the mutant gene from either parent can cause the condition. This differs from some other forms of the disease that may be recessive. Dogs' genetic status can be:

• Clear (N/N): No mutation; unaffected and cannot pass the disease.
• Carrier or Heterozygous (N/AxD): One mutated gene copy; may or may not show symptoms but can pass the gene to offspring.
• Affected or Homozygous (AxD/AxD): Two copies of the mutated gene; typically develop full disease symptoms.

Responsible breeding involves pairing carriers only with clear dogs to prevent affected puppies, alongside genetic screening for mating plans.

DNA testing for Alexander disease in Labrador retrievers

In the UK, veterinary genetic laboratories offer DNA testing to detect the presence of the GFAP gene mutation linked to Alexander disease. This test involves collecting a cheek swab or blood sample from your dog, which is then analysed in accredited labs like Laboklin.

Testing provides a crucial tool for breeders and owners alike. By knowing the genetic status of dogs, breeders can:

• Avoid producing puppies affected by this fatal disorder.
• Choose appropriate mating pairs, ideally carrier to clear, to limit gene spread.
• Safeguard the health and welfare of future litters.

If you plan to breed your Labrador or seek a puppy, ensure both parent dogs have undergone DNA testing for Alexander disease to minimise health risks.

Management and care for dogs with Alexander disease

Currently, Alexander disease has no cure or effective treatment. Management focuses on preventing the disease through responsible breeding rather than therapeutic care. Affected dogs show progressive neurological decline, leading to impaired movement and eventual paralysis.

Humane euthanasia is often the recommended decision to prevent prolonged suffering once signs become severe. Veterinary advice and ethical considerations are paramount when facing this heartbreaking diagnosis.

Why responsible breeders and owners should use DNA testing

DNA testing for Alexander disease exemplifies how modern genetic tools empower breeders and owners to promote healthier dogs and reduce inherited diseases in popular breeds like the Labrador retriever. These measures reflect a commitment to animal welfare, the breed's longevity, and more informed pet ownership.

Before acquiring a Labrador puppy, ask breeders for health clearances and mutation test results. If you own a Labrador, consider testing to be an informed advocate for your pet’s health and future breed welfare.

Common questions about Alexander disease in Labradors

What symptoms should owners watch for?

Primary symptoms include tremors, stiffness, difficulty walking or coordinating movements, and muscle weakness appearing in puppies as young as 4 to 6 weeks old.

Is Alexander disease treatable?

Currently, there is no cure or treatment, and the disease is progressive and fatal usually within the first year of life.

Can I get my Labrador tested?

Yes, your vet can collect a sample for genetic testing via approved laboratories to determine your dog's status and help guide breeding decisions.

How should breeders manage carrier dogs?

Breeders should mate carriers only to clear dogs to avoid affected offspring and gradually reduce the disease gene's incidence.

Conclusion

Alexander disease or leukodystrophy in Labrador retrievers is a rare but devastating inherited neurological disorder. Early symptoms in puppies lead to progressive paralysis and often humane euthanasia. Genetic testing for the GFAP mutation plays an essential role in responsible breeding, allowing owners and breeders to reduce the incidence of this fatal disease.

By promoting awareness, encouraging DNA testing, and supporting ethical breeding decisions, we can help safeguard the health and welfare of future generations of Labradors. If you own or plan to acquire a Labrador retriever, consider genetic screening to make informed, responsible choices and preserve this wonderful breed’s legacy.