Complement 3 deficiency / C3 deficiency (C3-related) - Brittany Spaniel

What does this test examine?

This genetic test analyses the C3 c.2136delC variant in the Brittany Spaniel. The disorder is known as Complement 3 deficiency, C3 deficiency, complement component 3 deficiency and hereditary C3 deficiency. C3 encodes complement component 3, a key protein in the immune complement system.

What does this mean for the dog?

C3 is important for recognising and clearing pathogens and for regulating inflammatory responses. Dogs with two copies of the tested variant produce insufficient functional C3. Especially young dogs can therefore become more susceptible to recurrent bacterial infections, including respiratory infections, urinary tract infections and uterine infections. C3 deficiency is also linked with immune-mediated kidney disease, including membranoproliferative glomerulonephritis and eventual loss of renal function.

Recurrent bacterial infections, urinary tract problems and immune-mediated kidney disease can occur.

Practical value of this test

This test has practical value because it makes an inherited risk variant visible when ordinary observation cannot reliably identify it.

• The result distinguishes clear dogs, carriers and genetically affected dogs.
• Breeders can identify carriers and plan matings that avoid affected puppies.
• The test helps identify hidden risk variants in a line before a dog is used for breeding.
• In young dogs or families with matching signs, the DNA result gives clear direction for follow-up and selection.
• For breed clubs and breeding programmes, the test helps manage inherited risk without unnecessarily excluding valuable lines.

Inheritance and result

The trait is inherited as an autosomal recessive condition. A dog with N/N does not carry the tested deletion, N/delC is a carrier and delC/delC causes the genetically affected genotype.