Progressive Retinal Atrophy
Progressive retinal atrophy (PRA) is the collective term for a group of inherited diseases of the retina, all of which are incurable and invariably lead to total blindness. PRA is known to affect many breeds of dog and characteristics such as the age at which with the disease progresses can vary from breed to breed. In some breeds the age of onset is very early but with other breeds, dogs may not start to go blind until they are well into middle age, or even older. Unfortunately, it is a late onset form of PRA that our lovely breed appears to suffer from.
PRA is usually caused by an autosomal recessive mutation. This means that a dog must inherit two copies of the mutation, one from its sire and one from its dam for it to be affected. It also means that both parents of an affected dog must be carriers. If a dog inherits a single copy of the causal mutation from either of its parents and a normal copy of the same gene from the other parent then it will be a carrier: it will never develop PRA during its lifetime but will pass the mutation on to approximately half its offspring.
If the dog inherits two copies of the mutation it will develop PRA, but its eyes will be healthy until it reaches the ‘age of onset’ and clinical signs begin to develop. If an ophthalmologist examines a genetically affected dog before it begins to display clinical signs he/she will not be able to tell if the dog is affected and the dog will receive a clear eye certificate. An ophthalmologist can only tell a dog is genetically affected once the clinical signs of PRA have begun to develop. Then to further confuse us, secondary cataracts can also develop, frequently the local vet will attribute the early blindness to cataracts and the real cause is overlooked.
There are various scenarios for transmission, which given the limited gene pool for the British Gordon Setter increases the odds of the disease occurring. Two thirds of canine genetic disorders are recessive.
To explain this inheritance pattern ~
GREEN
DOGS - CLEAR
YELLOW
DOGS - CARRIER
RED
DOGS - AFFECTED
RED DOGS ~ AFFECTED will not show signs of the disease until approximately 7 years of age, having a vet check the eyes in the younger years will not tell you whether your dog is clear, carrier or affected. All of us with dogs over the age of about 10 that have received the all clear from an ophthalmologist can be assured that those dogs are either (green) clear or (yellow) carrier.
1.When two green dogs are mated, both parents being clear of the disease, all the puppies will be genetically clear.
2. When one parent is (green) clear and the other is a (yellow) carrier,approximately half of all the puppies will be (green) clear and half will be
(yellow) carrier, meaning 50% of the litter will be carriers.
3.When one parent is (green) clear and the other is (red) affected then all of the puppies will be (yellow) carriers.
4. When both parents are (yellow) carriers, then on average a quarter of their puppies will be (green) clear, a quarter will be genetically affected (red) and half will be (yellow) carriers. That’s 75% of the litter with mutant genes.
5.When one parent is (yellow) carrier and the other parent is (red) affected then half the puppies will be (yellow) carriers and half will be (red)
affected.
6. When both parents are (red) affected then all the offspring will be (red) affected.
Hip (and Elbow) Dysplasia
Hip Dysplasia (HD) is the malformation of the development of one or both ball and socket joints in the hip. The hip joint is composed of the socket, which is formed by the bones of the pelvis, and the "ball" (head) of the thigh bone (femur). Normally, this joint is very tight fitting, however if suffering from dysplasia there will be too much movement in the joint resulting in wear of the joint resulting in pain and lameness. The degree of hip dysplasia present is indicated by a score assigned to each hip. Using the BVA/AVA system the hip score is the sum of the points awarded for each of nine aspects of the X-rays of both hip joints. The minimum hip score is 0 and the maximum is 106 (53 for each hip). The lower the score the less the degree of hip dysplasia present. In the UK an average (or mean) score is calculated for each breed scored under the scheme and advice for breeders is to use only breeding stock with scores well below the breed mean score.
The minimum age for hip scoring is one year, and each dog is only ever scored once under the scheme. Hip (HD) and Elbow Dysplasia (ED) is a multifactoral, genetically based disease which is greatly influenced by environmental factors. The modes of inheritance of HD and ED are complex and the degenerative changes occur with growth if the unfavourable genetic and environmental factors are present. Due to this complexity, normal
hipped/elbowed dogs can produce offspring with all degrees of dysplasia and dysplastic dogs can produce normal offspring.
The Gordon Setter clubs and KC encourage all breeders to X-Ray and score the hips of at least, all their breeding stock.The lower the score per hip/elbow, the better.
Treatment of HD is directed at the alleviation of pain, and in severe cases involves major (and expensive) surgery to replace the joint.