Scout's corner
Should I test my herding puppy for MDR1?
By Dr. Steve Pelton, DVM. Small-animal vet since 2000.
Your host
Scout, an Australian Shepherd puppy
This corner is for
Collies, Australian Shepherds and Mini Aussies, Shelties, German Shepherds and herding mixes.
Mixed breed? Read the corner that fits his body, not just the name on the paperwork. An 80-pound Lab-Shepherd mix belongs in Moose's corner.
The short answer
- Yes, ask your vet. Many herding dogs carry a gene change called MDR1 that makes some common medicines dangerous for them.
- About 70% of Collies and 50% of Aussies tested carry it.
- It's one cheek swab, done once, through your vet.
- Keep the result with his records and tell every vet who treats him, including an emergency clinic.
What MDR1 does
The MDR1 gene's normal job is to pump certain drugs back out of the brain. In a dog with the mutation, the pump doesn't work right, so some common medicines can build up in the brain and cause serious, even life-threatening, reactions.
I'm not listing the drugs here, on purpose. Your vet knows them. What matters more is that if your herding puppy has been tested, nobody ever has to guess.
- ColliesAbout 70%
- Australian ShepherdsAbout 50%
- Miniature Australian ShepherdsAbout 50%
Less common, but possible: Shelties, German Shepherds, Old English Sheepdogs and herding mixes.
Three steps, once
- Ask your vet about the MDR1 cheek-swab test at a puppy visit.
- Keep the result with his records, and take a photo of it for your phone.
- Tell every vet who treats him, including an emergency clinic, whether he's positive or negative.
Make his card
Scout's MDR1 card
Fill it in, then print it for his collar folder or take a screenshot for your phone. It stays in this browser.
For every vet who treats me
My dog
MDR1 status: ________
Herding breed, not tested yet. Please check before giving medicines.
newpuppy.vet
Questions I get every day
What is MDR1 in dogs?
MDR1 is a gene whose normal job is to pump certain drugs back out of the brain. Dogs with the mutation have a pump that doesn't work right, so some common medicines can build up in the brain and cause serious, even life-threatening, reactions. Your vet knows which ones.
Which breeds carry MDR1?
According to Washington State University, which runs the main testing lab, about 70% of Collies and about 50% of Australian Shepherds and Miniature Australian Shepherds tested carry it. It's less common but possible in Shelties, German Shepherds, Old English Sheepdogs and herding mixes.
How do you test a puppy for MDR1?
With a cheek-swab DNA test you can do through your vet. It only needs to be done once, and it tells you whether your puppy has zero, one or two copies of the mutation. Keep the result with his records and tell every vet who treats him.
Where this comes from
- Washington State University, Program for Individualized Medicine. Breeds commonly affected by MDR1 mutation (Collie 70%, Australian Shepherd 50%, Miniature Australian Shepherd 50%).
General education, not veterinary advice. Your vet's plan for your puppy comes first.