Progressive Retinal Atrophy (PRA-RHO) in dogs

Progressive retinal atrophy is a painless but irreversible condition that can affect the eyes of dogs, which leads to progressive loss of vision to the point of ultimate permanent blindness.

Progressive retinal atrophy or PRA comes in a variety of different types and variants depending on their action and mode of heredity, and the impact that they have on affected dogs.

PRA-RHO is a specific type of progressive retinal atrophy in dogs that occurs due to a mutation or anomaly in the dog’s RHO gene, which is a gene that pups inherit from their parents. This type of progressive retinal atrophy is inherited by means of autosomal dominant heredity, which means that even if only one of the two parent dogs carries the mutated RHO gene and the other dog is healthy, their pups will still inherit the condition.

In this article we will look at progressive retinal atrophy PRA-RHO in more detail, including sharing information on how dogs develop the condition, what type of dogs are most at risk of the condition, how it affects dogs, and how the condition can be avoided or prevented. Read on to learn more.

What is progressive retinal atrophy RHO?

Progressive retinal atrophy is a hereditary eye disorder that causes the degeneration of photoreceptor rod cells in the eyes, which are a type of cell that enables dogs to see properly in dim lighting.

Dogs with the condition are born with normal vision, but as they get older, they gradually begin to lose their sight, beginning with problems at the edges of their peripheral vision and an inability to see properly and make out shapes and contrasts in darkness and dim lighting, but progressing to affect the dog’s vision in full light as well.

Over time, this loss of vision causes full blindness, but progressive retinal atrophy is slow to develop, which means that with early diagnosis, dog owners can take steps to acclimatise their dogs to their loss of vision and help to retain and improve their quality of life as their vision worsens.

Why do dogs develop the condition?

Progressive retinal atrophy is hereditary, which means that is not contagious and can only be passed on from one dog to another by means of inheritance. A parent dog that has progressive retinal atrophy – or that possesses one of the gene mutations for the condition, even if they have yet to begin losing their own vision – will pass the condition on to their own young.

PRA-RHO is a dominant form of the condition, which means that only one parent dog carrying the mutated RHO gene for the condition is necessary in order for their offspring to develop PRA in their turn.

What sort of dogs are at risk of PRA-RHO?

The genetic mutation that causes PRA-RHO has been identified within blood lines of the bullmastiff and mastiff dog breeds, and pedigree dogs of these two respective breeds are considered to be those most at risk of the condition, due to the manner in which a dominant hereditary condition can spread quickly throughout large parts of a breed’s wider gene pool.

However, any dog with just one mastiff or bullmastiff parent – or a pup that is a cross-breed between a mastiff and a bullmastiff – also runs the risk of inheriting the condition due to the dominance of the mutation that causes this form of PRA.

In affected dogs, the condition usually becomes apparent between the ages of six months and three to four years old, although less commonly, the condition may not present until a little later on.

How is PRA-RHO passed on from dog to dog?

If just one of the two parent dogs in any mating match carries the RHO gene mutation that causes PRA-RHO, their offspring will in turn inherit the mutation and so, develop PRA.

If both parents of the litter carry the gene mutation for RHO, the condition will tend to progress more rapidly than is normal in a dog with one affected and one healthy parent.

Can PRA-RHO be cured?

Progressive retinal atrophy cannot be reversed or cured, and can only be prevented by pre-breeding health screening of dogs from at-risk breeds to confirm their status prior to breeding.

However, the progression from normal vision to total blindness in the condition is gradual and often slow, allowing the dog and their owner time to adjust and make accommodations for the dog’s progressively failing vision.

Breeding and buying healthy dogs

Breeding any dog with PRA-RHO means that their own litter will be affected, regardless of the status of the other parent dog, and said litter will not only suffer from PRA themselves, but be capable of further spreading and passing on the condition to their own offspring if bred from.

However, a DNA test is available to allow breeders to find out their own dog’s status for PRA-RHO prior to making a decision to breed from them, which means that breeders can then make an informed decision about the suitability of any dog as breeding stock.

Dogs that test positive for PRA-RHO should not be bred from, even to a mating partner that has tested clear, because they will still pass the condition on to their own young.

Learning that an adult dog carries the PRA-RHO gene also provides important information for the dog’s owner, which means that while they will not be viable breeding stock, being able to predict future blindness in the dog in question allows the owner to make decisions and accommodations for the dog before their vision fails, to make their lives easier.

Potential buyers of bullmastiff and mastiff puppies are urged to only make a purchase from breeders who perform PRA-RHO DNA testing on their breeding stock prior to breeding, and that make the results of said tests available to puppy buyers to confirm their status.