MDR1 ~ Drug Sensiivity Gene Mutation

Many people, including many vets, still do not  know of the MDR1 gene mutation although the word is getting out.  We ask you to please share this information with anyone you know who owns a dog be it herding breed or not.  If they share it with everyone they know and so on, it could save a life and spare a lot of heartache.  Please pass this along.

The WSU website is the primary source for the information provide on this website.

Herding breed dogs and any cross breed dog with herding breed in their bloodlines can carry a genetic mutation that makes them sensitive to certain drugs. Use of those drugs can cause serious neurological illness or death.

Fortunately, there is an extremely accurate DNA test that will let you know whether your dog has this mutation. All you have to do is provide a cheek swab.  It isn't even necessary to go to the vet.


What is MDR1?

MDR1 is the abbreviated name of a gene called Multi-Drug Resistance 1.  A mutation of this gene causes sensitivity to Ivermectin and a number of other drugs. Dogs having two copies of the mutation will lead to drug reactions, but having a single copy can also confer some sensitivity with some drugs. Dogs with this mutation have a transport defect - the drug goes in to their brains, fails to be transported out, and builds up to toxic levels. This causes serious neurological problems including seizures and sometimes death.

Heartworm preventive is safe: The medications used in monthly heartworm preventives are at levels safe enough even for dogs with the MDR1 mutation, as long as the preventives are given according to the manufacturers' recommended dose. However........


Horse owners and neighbors of horse ower, beware..........

If your canine assistant laps up some of your horse’s paste dewormer or eats the manure of a horse who has been recently dewormed, he could temporarily or permanently lose his eyesight or even die, depending on the amount ingested.



How do I know if my dog has this gene mutation?

There are only two ways to know if an individual dog has the mutant MDR1 gene, by parentage verification or having the dog tested.   

We personally recommend that you only buy from breeders that can provide you with test results of breeding stock upon request.  If both parents have tested negative for this gene then the puppies will not be effected.  If you do not know about the parents or if one of the parents is a carrier then we strongly advise you test your dog.   The most important thing to remember is that knowledge equals power.  Knowing if your dog has this gene can be all it takes to make sure your dog lives a long healthy life.  

Make sure to share your dog's MDR1 status with your vet in the unfortunate event your dog has a reaction.  Our understanding is that the sooner the reaction is diagnosed and treatment is started the better chance you have of a good outcome.  

Revisiting the WSU website we have recently found updated information.

The percentages listed in the past were 32% of standard Australian Shepherds and 49% of Mini Aussies carried at least one copy of the gene.  Now they have posted that 50% of each are affected with the mutated gene.  

As more dogs are tested the facts will change.  More breeds will probably be added to the list of affected breeds and obviously the percentage of affected dogs are subject to change.

The MDR1 information will probably be updated many times after this posting and we most likely won't keep this page updated with the latest statistics but in our opinion that's not important.    You can always find the latest information by doing a Google search on MDR1.  What is important to us is to educate as many people as we can that the problem exists.

When we first put MDR1 information on our webpage there were very few labs that would run the test.  The number of labs that have been licensed for MDR1 in Australian Shepherds has grown.  Many labs preform MDR1 testing but a lot of them aren't licensed for Aussies.  If you shop around you can find tests for around $50 or so for testing these days.  


How often do I have to get my dog tested?

Only once.  A dog either has one copy or two copies of the mutated gene at birth or it does not.  This is not something a dog can acquire.





~ What breeds are affected?

~ What drugs can cause a reaction?

~ How do I know if my Mini Aussie has the MDR1 gene mutation?

~ How do I get the test done?

~ What do the MDR1 test results mean?


~ MDR1 Breeding Guidelines for dog breeders according to WSU.