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Health and the Lancashire Heeler
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This extract is taken from 'The Kennel Club Charitable Trust Update 2010' published in June Lancashire Heelers tested to date are 80 of these 47 were clear 30 carriers and unfortunately 3 affected dogs. This is for dogs tested in the UK
The AHT had completed DNA tests for 2371 dogs, 8 different breeds, from 30 different
countries.
BREEDING ADVICE
The testing figures obtained to date indicate, that for some breeds at least,the percentage of dogs that carry the PLL mutation is extremely high. For this reason the
Animal Health Trust believes that eliminating all carriers from these breeding populations is inadvisable in the short term and advises breeders to consider all their dogs for
breeding, regardless of their PLL genotype. CARRIER dogs can be bred with, but should
only be bred to DNA tested CLEAR dogs. Because carriers are at a low risk of developing PLL we recommend that all puppies with a CARRIER parent should be DNA tested,
so that the CARRIERS can be identified and monitered clinically throughout their lives. In exceptional circumstances GENETICALLY AFFECTED dogs may even be considered for breeding, if they are outstanding examples of the breedfor example, but, as with
CARRIERS, should only be mated to CLEAR dogs. All offspring of a GENETICALLY
AFFECTED parent will be CARRIERS, so should be clinically monitered throughtout
their lives. The practice of including CARRIERS for breeding should be followed for at
least two generations, to allow the PLL mutation to be slowly eliminated from the population without severely reducing the genetic diversity of the breed.
Dr Catheryn Mellersh (Animal Health Trust)
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RESEARCH FINDINGS
PLL has long been considered to be a recessive condition, meaning that dogs need to inherit two copies of the causative mutation before they develop clinical signs of the condition. Dogs that carry a single copy of a recessive mutation (herterozygotes) are free from clinical signs themselves but will pass the mutation onto approximately half of any offspring they have. A surprising finding that emerged from the extensive research was that some dogs that carry a single copy of the PLL mutation develop bilateral PLL. The exact number of carriers that develop PLL is difficult to estimate, for various reasons, including the fact that owners and breeders tend to tell researchers about their clinically affected dogs more often than they report their unaffected dogs. However, we currently estimate that the percentage of carriers that develop clinical PLL is likely to be less than 5% in most breeds and understanding why some carriers develop PLL whereas the vast majority do not is the subject of continued investigation.
The 'clinically affected carrier phenomenon' is not restricted to a single breed: robust data is available from clinically affected carriers of at least six different breeds, indicating the phenomenon is real, and not restricted to single breeds, or isolated lines within breeds.
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