Progressive Retinal Atrophy (PRA)
Progressive Retinal Atrophy (PRA) is an untreatable, irreversible, inherited eye disease that causes degeneration of the retina and leads to complete blindness.
While PRA has a number of forms and affects many breeds. Irish Setters suffer from an ‘early onset’ kind of PRA known as rod-cone dysplasia 1 or rcd 1.
· Irish Setter PRA (rcd1) is unique in its early onset with affected animals becoming blind at an early age.
· The rcd1 form of PRA is passed on by a simple autosomal recessive gene.
· Clear dogs have no copies of the PRA gene. They will never develop the disease nor will they pass it on to their offspring.
· Carriers have one copy of the defective PRA gene and one copy of the normal gene. They will not develop the disease but may pass a defective gene on to a proportion of their offspring.
· Affected dogs have two copies of the gene that causes PRA and will go blind.
Canine Leucocyte Adhesion Deficiency (CLAD)
Canine Leucocyte Adhesion Deficiency (CLAD) is a recessive genetic disorder that results in a fatal immunodeficiency disease in which affected puppies die due to multiple and intractable bacterial or viral infection. CLAD was first identified in the USA.
In 1999, the mutation causing CLAD in Irish Setters was identified and a genetic test developed. CLAD can be difficult to diagnose so the simple once-only test is a significant development as use of the test will enable breeders to eliminate the risk of producing affected dogs.
The test accurately identifies clear, carrier and affected animals.
· Clear dogs have no copies of the CLAD gene. They will never develop the disease nor will they pass it on to their offspring.
· Carriers have one copy of the defective CLAD gene and one copy of the normal gene. They will not develop the disease but may pass a defective gene on to a proportion of their offspring.
· Affected dogs have two copies of the mutant gene that causes CLAD and will develop the disease.
Both of these diseases have impacted on the breed overseas, leading to development of genetic tests through extensive research.
PRA and CLAD are inherited quite independently and each has an autosomal recessive mode of inheritance, so any affected animal must have two defective genes for the particular disease – one from each parent.
It is important to understand that the tests are specific gene tests so results are unequivocal: dogs/bitches are classified with certainty as clear, carrier or affected. This makes it possible to prevent the disease, and also to eliminate the causative genes and the need for further testing.