DNA Testing for Early Onset Progressive Retinal Atrophy (EOPRA) in Dogs

Progressive retinal atrophy (PRA) is a hereditary canine health condition that leads to progressively worsening blindness, which unfortunately cannot be reversed or cured. While PRA is painless, the vision loss it causes can drastically affect a dog’s quality of life and poses challenges for both the dog and their owner.

Typically, PRA develops in mature or senior dogs, but one specific type, early onset progressive retinal atrophy (EOPRA), appears much earlier—often within the first few months of a puppy's life. EOPRA progresses quickly to near-total blindness.

EOPRA is inherited via faulty genes, making it more prevalent in specific breeds. In the UK, the Portuguese water dog puppies are at higher risk. Thankfully, new DNA testing introduced by the Optigen laboratory now enables breeders and owners to determine the EOPRA status of their dogs, supporting more responsible breeding.

This guide explains how EOPRA is inherited, why Portuguese water dogs are susceptible, and how DNA testing is used to prevent the condition. It also highlights best practices for breeders to safeguard the breed's health.

What is Early Onset Progressive Retinal Atrophy?

EOPRA is a form of progressive retinal atrophy that affects young dogs, contrasting with other forms that manifest later in life. Also called retinal dysplasia, symptoms often appear before a puppy reaches six months old, though they can occasionally emerge slightly later.

Unlike other PRA types that develop slowly over months or years, EOPRA typically leads to significant vision loss and potential blindness within a short timeframe.

While EOPRA does not cause physical pain, it requires dedicated care from owners to help blind or visually impaired dogs maintain a safe and fulfilling life.

Why Are Portuguese Water Dogs at Risk?

Due to the limited gene pool in pedigree breeds like the Portuguese water dog, hereditary conditions such as EOPRA can spread relatively rapidly through the population. This occurs because affected or carrier dogs may pass on faulty genes to offspring, especially if testing and responsible breeding practices are not followed.

The Portuguese water dog breed has shown a higher-than-average incidence of the gene mutation linked to EOPRA, making DNA screening essential for breeders and owners.

How Is EOPRA Inherited?

EOPRA spreads through autosomal recessive inheritance, meaning a dog must inherit two copies of the faulty gene (one from each parent) to be affected. The combination of the parents’ genetic status determines the puppies’ likelihood of being affected, carriers, or clear:

• If both parents are clear, offspring will be clear.
• If both parents are affected, all puppies will be affected.
• If both parents are carriers, approximately 25% of puppies will be affected, 50% carriers, and 25% clear.
• If one parent is carrier and the other affected, 50% of puppies will be affected and 50% carriers.
• If one parent is carrier and the other clear, 50% will be carriers and 50% clear.
• If one parent is clear and the other affected, all puppies will be carriers.

DNA Testing for EOPRA: How It Works and Why It Matters

DNA testing for EOPRA involves a simple sample collection by your vet, which is sent to a specialist lab such as Optigen. The test identifies whether a dog is clear of the gene, a carrier, or affected.

This information is invaluable for breeders planning litters: by avoiding mating two carriers or affected dogs, they can prevent producing affected puppies and reduce disease prevalence.

It’s crucial that Portuguese water dog puppies are bought from breeders committed to transparent health testing, including EOPRA screening of parent dogs. Responsible breeders will not breed affected dogs and will carefully select mates to avoid carrier pairings.

Responsible Breeding and Health Screening

Beyond EOPRA, breeders should also screen for other inherited conditions common in the breed to promote overall health and welfare.

Breeders are encouraged to:

• Perform comprehensive genetic health tests before breeding.
• Only breed dogs that are clear or appropriately managed carriers.
• Inform prospective owners about health testing results.
• Avoid breeding puppies from two carriers or any affected dogs.

Following these practices helps safeguard the breed's future, reducing the incidence of EOPRA and improving the lives of both dogs and owners.

Summary

Early onset progressive retinal atrophy is a serious hereditary eye condition leading to early blindness in affected dogs, notably in Portuguese water dogs. While the condition has no cure, modern DNA testing offers a powerful tool to prevent affected puppies through responsible breeding.

For prospective owners and breeders, discussing EOPRA testing and results is an important step to ensure healthy puppies with a better quality of life. Working with reputable breeders who prioritise genetic screening supports the welfare and future of the breed.