PRA RCD2 Testing for Rough & Smooth Collies Explained

Progressive retinal atrophy (PRA) is a common inherited eye disease causing gradual and irreversible blindness in dogs. Among its various forms, the rough collie and the smooth collie breeds are particularly affected by the RCD2 variant of PRA. This article explains RCD2 PRA, which dogs it affects, and why testing is essential for maintaining the health of these breeds through responsible breeding.

What is RCD2 Progressive Retinal Atrophy?

RCD2, or rod-cone dysplasia type 2, is a form of PRA characterised by the early degeneration of rods and cones—the retina's light- and colour-sensitive cells—leading to rapid vision loss. Unlike other PRA types that may show symptoms from three years onward, RCD2 signs can appear as early as six weeks old, with most affected dogs losing night vision around this time and becoming blind by 6-8 months.
In RCD2, rod cells degenerate faster, causing night blindness first. Eventually, cone cell damage leads to complete blindness.
This early and rapid progression makes understanding RCD2 critical for breeders and owners of affected breeds.

Which Dogs Are Affected?

The RCD2 variant specifically affects the rough and smooth collie breeds. Dogs with partial ancestry of these breeds may also carry the gene, potentially passing it on.
This inherited condition manifests early, with puppies typically showing difficulty seeing at night by six weeks old and potentially complete blindness by twelve weeks.
Untested breeding of carriers inadvertently spreads the condition, hence the importance of genetic testing.

How Is RCD2 Inherited?

RCD2 PRA is an autosomal recessive condition. This means that:

• If neither parent carries the gene mutation, puppies will not inherit or carry the fault.
• If one parent is a carrier and the other clear, puppies have a 50% chance of being carriers and 50% chance of being completely clear.
• If both parents are carriers, 25% of puppies will be clear, 50% carriers, and 25% affected and likely to develop blindness.
• If one parent is affected and the other clear, all puppies will be carriers but not affected.
• If one parent is affected and the other a carrier, 50% will be carriers and 50% affected.
• If both parents are affected, all puppies will be affected.

Understanding these inheritance patterns is essential for breeders to avoid producing affected puppies.

Why Is Genetic Testing for PRA RCD2 Important?

Since symptoms of the disease can appear and progress rapidly, affected puppies are typically identified early by owners and breeders and ideally removed from breeding programmes. However, many healthy appearing dogs may be carriers of the faulty gene and unknowingly pass it on if untested.

Genetic testing identifies whether a dog is clear, a carrier, or affected. This information guides breeders in selecting mating pairs responsibly, dramatically reducing the incidence of PRA RCD2 in future generations.

How Does PRA RCD2 Testing Work?

Testing requires a DNA sample, commonly collected via a cheek swab by a vet. This sample is sent to a laboratory specialising in veterinary genetic testing, such as those listed on The Kennel Club's website.

The test uses molecular techniques to detect the presence of the specific gene mutation responsible for RCD2. Results typically come back within one to two weeks and detail the dog's genetic status as clear, carrier, or affected.

Responsible Breeding Practices to Prevent PRA RCD2

To protect the health of rough and smooth collies, breeders should:

• Test all breeding dogs for PRA RCD2.
• Avoid breeding two carriers together to prevent affected offspring.
• Prefer mating clear dogs or clear to carrier, carefully managing carrier status.
• Inform puppy buyers about testing and genetic health to promote wider awareness.

Following these steps helps maintain breed vitality and reduces suffering due to blindness.

Additional Resources and Support

For more general information about progressive retinal atrophy in dogs, see Progressive Retinal Atrophy (PRA) in Dogs.

If you are looking to find a rough collie puppy or a smooth collie puppy, consider breeders who responsibly test for hereditary conditions like PRA RCD2 to secure a healthy future for your new companion.

Testing and responsible breeding are key to combating this hereditary blindness and preserving the legacy of beloved collie breeds.