2. CA only affects young dogs, all the cases reported so far (13 puppies out of 7 litters in the UK and 3 puppies out of 2 litters in Denmark, born between November 1990 and March 1997) have been under one year old. Therefore, even though an adult dog may be a descendant of one or more of the proven carriers it is highly unlikely that it will develop CA, although it could be a carrier.
3. The clinical signs of CA are as described in a separate report.
4. CA appears to be restricted to one family line only and all cases reported so far have one or more of the proven carriers on both sides of the pedigree.
5. From the above information, and by studying the pedigrees, together with the number of affected puppies in the litters, it has been shown that the mode of inheritance of CA is that of a simple recessive gene i.e.
a) for affected puppies to be produced both the sire and the dam must be carriers.
b) it is the unidentifiable carriers which spread the disease throughout the breed (the puppies which are affected never reach the age when they could be bred from and therefore pose no threat).
c) a brief example of the possible matings are shown below:
i) a carrier mated to a carrier will produce puppies of the following status:
6. a) With a policy of out crossing it is possible to prevent the production of affected puppies and, if this were continued over a number of generations, the frequency of carriers being produced would decrease. The probably of descendants of proven carriers being carriers themselves would, on average, be reduced by a half in each subsequent generation e.g.
b) Under the guidance of geneticist, Dr. Bruce Cattanach, the Committee of the ISCGB have formulated a control scheme to help prevent the production of affected puppies and also to reduce the frequency of production of carriers within the breed.
Please remember that if you have any questions, no matter how trivial they may seem, do not hesitate to contact me. You can ring me evenings or weekends on 01522 792743 (INT 44 1522 792743) or you can write to me at the following address:
28 Park Lane
UPDATE: Another case of CA has been reported. This was a puppy bitch from an accidental grandmother to grandson mating. The bitch was actually 14 months old when she was put to sleep but I understand that the symptoms were very advanced and Dr. Wheeler had said it was the worst case he has seen so far, so one can only assume that the bitch had been affected for some time. This brings the total so far to 14 puppies from 8 litters in the UK and 3 puppies from 2 litters in Denmark.
Issued by Pat Wilkinson (Health Sub Committee (Ataxia) ISCGB 6/18/98
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