Before signing anything for an Australian Shepherd in France, a buyer should ask for the MDR1 result in writing, confirm that the sample is tied to the individual puppy by microchip or tattoo, and check the date on the laboratory report. The test is a DNA test, so the result does not change with age or vaccination, but the document still has to belong to that dog and that dog only. If the seller cannot show a result matched to the puppy, the buyer is being asked to accept a verbal assurance about a heritable drug sensitivity.
MDR1, also called ABCB1, is the gene behind a defect in the blood brain barrier pump that normally keeps certain drugs out of the central nervous system. Dogs with two copies of the mutation are at risk of severe neurologic toxicity from ivermectin at doses that are safe for other dogs, and from a number of other drugs. This is why the result matters at purchase, not after the first deworming.
What should an Australian Shepherd buyer ask about MDR1 before signing?
Ask for the laboratory name, the report number, the date of sampling, and the identifier that links the sample to the puppy. A useful request is a copy of the original report, not a summary typed into a message. The report should name the dog or the litter and carry a microchip number, a tattoo number, or a registration number that matches the paperwork the buyer is about to sign.
Ask who was tested. A tested dam and a tested sire tell the buyer something about the parents, but they do not describe the puppy. Each puppy inherits one copy of the gene from each parent, so the combination in an individual puppy is not predictable from the parents' results alone unless both parents are clear. When a breeder says the line is clean, the follow-up question is which dogs in that line were tested and when.
Ask what happens if the result is missing. A buyer looking at a French LOF Aussie puppy can treat the MDR1 result as one item in the purchase file, alongside the pedigree, the health certificates, and the written answers to questions about the parents. A seller who has nothing to show is not necessarily dishonest, but the buyer should know that the information is absent before money changes hands.
How is an MDR1 result read in a breeding decision?
The result comes back in three categories. Clear means the dog carries no copy of the mutation. Carrier means the dog carries one copy. Affected means the dog carries two copies, one from each parent.
A clear dog passes a normal copy to every puppy. A carrier passes the mutation to roughly half of its puppies, and the other half receive the normal copy. An affected dog passes the mutation to every puppy. Two carriers can produce affected puppies. A carrier bred to a clear dog cannot produce an affected puppy, but it can produce carriers.
For a buyer, the practical reading is narrower. A carrier puppy is not expected to show the drug sensitivity, because one normal copy is generally enough for the pump to work. An affected puppy is the one that needs a different preventive plan from the first weeks in the new home. The breeding decision belongs to the breeder, but the buyer is entitled to know which category applies to the dog in front of them, because it changes the veterinary instructions that come with the puppy.
A result is also a dated document. Laboratories issue a report on a specific sample collected on a specific day. If a seller offers an old report from a previous litter and applies it to a new puppy, that is not a result for the puppy. The same applies to a result from a sibling. DNA does not drift, but identity does, and the report has to follow the dog.
Where does the test result belong in the puppy's file?
The result belongs with the documents the buyer takes home: the pedigree or registration papers, the vaccination record, the deworming record, and any health screening certificates for the parents. It should be a copy of the laboratory report, not a handwritten note. If the puppy is microchipped, the chip number on the report should match the chip number in the paperwork.
The buyer should also keep the result in a place the veterinarian will see it. The first veterinary visit is the right moment to hand over the MDR1 status, because it determines which parasite preventives are appropriate. Many monthly heartworm products contain ivermectin or a related compound, and the dose in those products is designed for dogs with a normal pump. For an affected dog, the veterinarian will choose an alternative.
How does the result carry into the first year of preventive care?
For a clear or carrier dog, routine preventive care follows the usual schedule, with the usual products. The result is still worth keeping in the file, because it is information the veterinarian may want if a neurologic reaction ever occurs.
For an affected dog, the first year is a series of small decisions. Heartworm prevention should be selected by the veterinarian with the MDR1 status in hand. Dewormers, flea products, and any drug given for nausea, diarrhea, or pain should be checked against the list of compounds that interact with the defective pump. Some of these are common, and a few are used without a second thought in dogs that are clear.
The owner's job is not to memorize the pharmacology. It is to make sure the MDR1 result travels with the dog: to the first clinic, to any emergency visit, and to any new veterinarian after a move. A copy in a folder and a note in the clinic file solve most of the problem.
A buyer who asks for the report, checks the identifier, and understands the three categories is in a position to make a decision with the information available. The test does not predict everything about a dog's health, but it answers one question clearly, and that answer is worth having before the puppy comes home.
A test result in the file answers only half of the question. The other half is what a breeder is willing to show before money changes hands, and how those answers shape the puppy's first year. Screening paperwork, eye and hip checks, and the breeder's willingness to discuss them all belong in the same conversation. Owners who want a structured way to raise these points can use these breeder screening questions, which cover what proof to request, why a verbal assurance falls short, and what the answers should change about care.
The figures and decision rules summarized above follow the published guidance of the WSU MDR1 programme, which sets out what an Australian Shepherd buyer should ask about MDR1 before signing, how a result is read in a breeding decision, where the test result belongs in the puppy's file, and how it carries into the first year of preventive care. Owners who want the primary source rather than a summary can consult that programme directly, and veterinarians can use the same material when counseling a buyer.