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A DNA test for Multidrug Resistance (MDR1) in Collies.
What is MDR1?
A DNA test for MDR1
"Dangerous drugs" for oversensitive dogs
Breeds at risk
Oversensitivity for certain drugs was first found in Collies, originally the
disorder was called "Ivermectine oversensitivity" or "Ivermectine toxicity".
Over the years it became clear that Ivermectine is just one of the drugs causing
problems for the animals suffering from oversensitivity and that it is not only
the Collie that suffers from this genetic disorder.
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Dr. Mark Neff and his co-workers showed that the mutant allele mdr1-1Δ
originates from an animal in the working sheepdog populations in Great Britain before
the isolation of breeds by registry, so before ca. 1873. From there on the mutant allele
was passed on to many modern Collie-breeds today and probably to other breeds as well.
Approximately three of every four Collies in the United States have at least one
mutant mdr1-1Δ allele. The frequency is about the same in France
and Australia, so it is likely that most Collies worldwide have the mutation.
The MDR1 mutation has not only been found in Collies and related
breeds like Shetland Sheepdogs (Shelties), Border Collies,
Australian Shepherds, Australian Cattledogs
and Old English Sheepdogs, but also in German Shepherds, White Swiss Shepherds,
Long-haired Whippets, Silken Windhounds and a variety of mixed-breed dogs.
In general, we should be aware that in the past, when breeds were developed,
often breeding stock of other populations (breeds) was used to improve certain
characteristics. In the process of introducing the desired qualities (genes)
into a breed, it cannot be avoided that many neutral as well as undesirable
genes cross the barrier between breeds.
For the time being, in all cases where similar clinical symptoms of
oversensitivity for drugs are found in breeds with "family ties" with the
original British working sheepdogs or their descendants, checking with the
MDR1 test would be advisable. If it can be proven that the defective
allele mdr1-1Δ is present, applying that DNA test will help the breeders
in their selection against the disorder. Even more important, it will help the
owners of pet dogs in avoiding the negative effects of wrong medication in
animals suffering from this devastating genetic disorder.
Breeding policy
Testing for MDR1
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