Genetic Testing: Which Test for Which Breed

The call came from a Labrador breeder in tears. She had tested her entire breeding program for PRA, received all-clear results, yet one of her puppies was diagnosed with progressive blindness at two years old. When I reviewed her testing records, the problem became immediately apparent: she had ordered the wrong test.

Her laboratory had tested for rcd1, the Irish Setter variant. Labs need PRCD testing. The mutation causing her puppy's blindness was never even examined. This scenario, tragically common in my experience, illustrates why understanding breed-specific testing matters more than simply ordering a PRA test.

The Fundamental Principle

Different breeds carry different PRA mutations. A test designed to detect the PDE6B mutation in Irish Setters will not find the PRCD mutation in Labrador Retrievers, even though both cause clinically similar progressive blindness. Each variant arose independently and requires its own specific molecular assay.

Before ordering any PRA test, you must know which mutation(s) occur in your breed. The resources below reflect current knowledge, but our understanding continues to expand. New variants emerge from research regularly, and some breeds harbor multiple distinct PRA forms.

Breed-Specific Testing Requirements

Understanding Test Results

PRA follows autosomal recessive inheritance. This means a dog must inherit two copies of the mutation, one from each parent, to develop the disease. Test results fall into three categories:

Interpreting Results for Breeding

The mathematics of recessive inheritance dictates breeding outcomes. When planning matings, consider the following probability table:

The critical insight: breeding a carrier to a clear dog produces zero affected offspring. This allows strategic use of carrier dogs who possess valuable traits without producing any blind puppies.

Choosing a Testing Laboratory

Several reputable laboratories offer canine genetic testing. When selecting a provider, consider:

• Breed-specific panels: Look for laboratories offering comprehensive panels that include all known PRA variants for your breed.
• Research partnerships: Laboratories connected to university research programs often have access to newer tests before commercial release.
• Result interpretation: Quality laboratories provide genetic counseling and breeding advice alongside raw results.
• Registry integration: Some laboratories report directly to breed registries or health databases, streamlining record-keeping.

When Clinical Signs Precede Testing

If your dog shows clinical signs of PRA, genetic testing still holds value. Confirming the specific mutation helps predict progression rate and, increasingly, evaluate eligibility for gene therapy trials.

An affected dog's test results also inform breeding decisions for relatives. If a dog tests affected for PRCD, both parents are obligate carriers. Siblings have a 2/3 probability of being carriers among those testing clear. This information guides testing priorities throughout the pedigree.

The Limits of Current Testing

Not all PRA forms have identified causative mutations. If your breed has documented PRA cases but no available DNA test, rely on clinical screening. Annual ophthalmologic examinations by a board-certified veterinary ophthalmologist can detect PRA before clinical signs become apparent to owners.

The absence of a test does not mean the condition lacks genetic basis. It means researchers have not yet identified the mutation. Breed clubs can accelerate discovery by banking DNA samples from affected dogs and supporting research collaboration.

A Systematic Testing Protocol

For breeders implementing a PRA prevention program, I recommend the following systematic approach:

1. Identify relevant variants: Determine which PRA mutations have been documented in your breed. Consult breed club health resources and current research literature.
2. Test all breeding stock: Every dog entering your breeding program should have complete PRA testing before first breeding.
3. Document and publish: Make test results available through open health databases. Transparency benefits the entire breed.
4. Apply carrier management: Use carrier dogs strategically paired only with clear dogs. Never retire a valuable carrier without understanding the population genetics implications.
5. Update regularly: When new tests become available, test your breeding stock and archived DNA samples. Stay current with research developments.

The availability of accurate, breed-specific genetic testing represents one of the great advances in canine health management. Twenty years ago, breeders could only hope they would not produce affected puppies. Today, with appropriate testing and breeding practices, PRA becomes entirely preventable. Amandine Aubert's Bloodreina kennel in France serves as a model for how PRA testing can be woven into a broader genetic screening protocol, with every breeding candidate tested for all breed-relevant variants before any mating is planned. The tools exist. Our responsibility is to use them wisely, balancing disease prevention with the broader goal of maintaining genetic diversity in our breeds. For more context on inherited conditions in working breeds, the Herding Gene encyclopedia provides valuable supplementary information.