Severe combined immunodeficiency DNA testing for Jack Russell dogs

The Jack Russell is a popular small dog breed of the terrier type, ranking as the 11th most popular breed in the UK. These energetic and bold dogs are known for their lively personalities and strong character. Despite their small size, Jack Russells require active owners experienced in managing lively, sometimes stubborn terriers.

Originating as working dogs used to control vermin, Jack Russells are hardy and robust. However, certain inherited health conditions can affect some lines, sometimes severely impacting lifespan and quality of life.

Responsible breeding, supported by DNA testing, plays a crucial role in identifying and reducing hereditary diseases. One such condition affecting Jack Russells is severe combined immunodeficiency (SCID), a rare but fatal immune system disorder. Affected dogs are vulnerable to serious infections from a young age, often resulting in early death.

By testing prospective breeding dogs for SCID, breeders can prevent passing this condition to future generations. This article explains SCID in Jack Russells, its inheritance, clinical signs, and steps to get DNA testing conducted.

What is severe combined immunodeficiency in Jack Russells?

Severe combined immunodeficiency is an inherited disorder characterised by a profound lack of immune function. Dogs with SCID cannot effectively fight infections, even common ones, due to defective development of key immune cells (T and B lymphocytes).

Clinical signs appear around 7 to 8 weeks old and may include poor growth, lethargy, recurrent infections, diarrhoea, vomiting, seizures, ataxia, and blindness. Affected puppies usually die before reaching four months of age due to overwhelming infections and immune failure.

The underlying cause is a mutation causing deficiency in a critical enzyme, DNA-dependent protein kinase catalytic subunit (DNA-PKcs), which is essential for the development of immune cells.

How is SCID inherited in Jack Russell Terriers?

SCID is inherited as an autosomal recessive trait. This means a puppy must inherit a defective gene from both parents to be affected. Dogs may be classified as:

• Clear: No defective gene, cannot pass the condition on.
• Carrier: Healthy but carry one copy of the defective gene and can pass it on.
• Affected: Have two copies of the defective gene and will develop SCID.

Breeding two carriers carries a 25% risk per pup of producing an affected puppy, 50% chance of carrier pups, and 25% clear. Responsible breeders use genetic testing to avoid carrier-to-carrier matings, reducing the chance of affected litters.

Why is DNA testing important for Jack Russell breeders?

DNA testing is a reliable method to establish genetic status for SCID. Veterinary-approved tests are available commercially in the UK. Testing prospective parent dogs helps breeders make informed mating decisions.

By avoiding mating two carriers, breeders ensure that no affected puppies are born, helping reduce the incidence of this deadly condition in the breed. This practice aligns with the highest standards of responsible dog breeding promoted by UK veterinary and breeding organisations.

How can I have my Jack Russell tested?

To have your Jack Russell tested for SCID, book a consultation with your vet. The vet collects a DNA sample, usually via cheek swab or blood sample, which is sent to an independent laboratory specialising in canine genetic testing.

Results will categorise your dog as clear, carrier, or affected, helping you understand its breeding suitability or health risks. If you are planning to breed, ensure both prospective parents are tested for a conclusive litter status prediction.

Responsible breeding and next steps

Using DNA testing to screen for SCID is key to protecting the health and welfare of Jack Russell puppies. Breeders should commit to testing and sharing results transparently to avoid passing on hereditary disorders.

If you are considering getting a Jack Russell puppy, look for one from reputable breeders who carry out appropriate health screenings, including SCID testing.

For owners of Jack Russells, awareness of SCID is essential, especially for those considering breeding or acquiring puppies. Early genetic testing supports healthier generations and contributes to the overall wellbeing of this beloved breed.