At-risk breeds

Which breeds carry the MDR1 mutation?

13 breeds with a documented MDR1 frequency, ordered high to low. Each number is the share of dogs in that breed carrying at least one copy of the mutation, per WSU — a population figure, not a verdict on your individual dog.

Source

Frequencies are transcribed directly from the WSU Veterinary Clinical Pharmacology Laboratory's breed table.

WSU — Breeds commonly affected by the MDR1 mutation (frequency table)

70%carry the mutation
Collie
The highest documented MDR1 frequency of any breed — roughly three of every four US Collies carry the mutation.
WSU — Breeds commonly affected by the MDR1 mutation (frequency table)Breed page & drug checker
50%carry the mutation
Australian Shepherd
About half of Australian Shepherds carry at least one copy of the MDR1 mutation, per WSU.
WSU — Breeds commonly affected by the MDR1 mutation (frequency table)Breed page & drug checker
50%carry the mutation
Miniature Australian Shepherd
The Miniature Australian Shepherd shares the standard Aussie's ~50% MDR1 frequency on the WSU table.
WSU — Breeds commonly affected by the MDR1 mutation (frequency table)Breed page & drug checker
50%carry the mutation
Long-haired Whippet
Roughly half of Long-haired Whippets carry the mutation — a notably higher frequency than the standard Whippet.
WSU — Breeds commonly affected by the MDR1 mutation (frequency table)Breed page & drug checker
30%carry the mutation
McNab
About 30% of McNab dogs carry at least one MDR1 mutant allele, per the WSU table.
WSU — Breeds commonly affected by the MDR1 mutation (frequency table)Breed page & drug checker
30%carry the mutation
Silken Windhound
Roughly 30% of Silken Windhounds carry the mutation — another sighthound on the WSU list.
WSU — Breeds commonly affected by the MDR1 mutation (frequency table)Breed page & drug checker
15%carry the mutation
English Shepherd
About 15% of English Shepherds carry an MDR1 mutant allele, per the WSU table.
WSU — Breeds commonly affected by the MDR1 mutation (frequency table)Breed page & drug checker
15%carry the mutation
Shetland Sheepdog (Sheltie)
Roughly 15% of Shetland Sheepdogs carry the mutation, per the WSU table.
WSU — Breeds commonly affected by the MDR1 mutation (frequency table)Breed page & drug checker
10%carry the mutation
German Shepherd
About 10% of German Shepherds carry an MDR1 mutant allele, per the WSU table — lower-frequency but documented.
WSU — Breeds commonly affected by the MDR1 mutation (frequency table)Breed page & drug checker
10%carry the mutation
Herding-breed cross
Roughly 10% of herding-breed crosses carry the mutation, per the WSU table.
WSU — Breeds commonly affected by the MDR1 mutation (frequency table)Breed page & drug checker
5%carry the mutation
Old English Sheepdog
About 5% of Old English Sheepdogs carry the mutation, per the WSU table — low, but not zero.
WSU — Breeds commonly affected by the MDR1 mutation (frequency table)Breed page & drug checker
5%carry the mutation
Mixed breed
Roughly 5% of mixed-breed dogs carry the mutation, per the WSU table.
WSU — Breeds commonly affected by the MDR1 mutation (frequency table)Breed page & drug checker
< 5%carry the mutation
Border Collie
Fewer than 5% of Border Collies carry the mutation, per the WSU table — far lower than the Collie despite the name.
WSU — Breeds commonly affected by the MDR1 mutation (frequency table)Breed page & drug checker

This is general information, not veterinary advice for your dog. It does not diagnose or prescribe. Always discuss any medication decision with your veterinarian before acting — they know your dog's full picture, including its MDR1 status if it has been tested. See our disclaimer and how we research.