Australian Shepherds, along with several other mostly collie-type breeds, 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 a 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.
How accurate is the test?
Extremely. It will identify the genotype of the dog tested: Exactly which form(s) of the MDR1 gene the dog has.
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 with the mutation will react to those drugs. Whether a dog reacts depends on the dosage of the drug. A dog may not react to very low doses, as with the amount of Ivermectin found in heart worm products. Typical doses of a variety of medications will cause reactions in dogs with two copies of the mutation, but some drugs – most notably several chemotherapy agents – can cause reactions in dogs with only one. 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.
Which drugs cause MDR1 reactions?
Ivermectin was the first drug recognized to cause a reaction, but it is far from the only one. Ivermectin at low dosage, as found in heartworm medications, will not cause a reaction. The larger doses needed for worming will. Other commonly administered drugs on the list include acepromazine and Imodium. Fortunately, there are alternative medications available if your dog requires treatment.
The drugs involved can be found listed below.
Dogs that do not carry an MDR1 mutation may safely receive the listed drugs.
Which breeds are affected?
How common is the MDR1 mutation in Aussies?
One in two Aussies has at least one copy of the gene.
How do I know if my dog has the MDR1 mutation?
If your dog has already reacted to one of the listed drugs, it has the mutation. However, reactions can be so dangerous to your dog it is advisable to have the dog tested so you know whether it is sensitive before it receives any of these drugs.
How do I get the test done?
For those in North America, The test is available through Washington State University. GO COUGS!!!!! :) Information can be found on their website: www.vetmed.wsu.edu/announcements/ivermectin/
What do the MDR1 test results mean?
This is a DNA mutation test. It will determine whether or not a dog has the MDR1 mutation and, if it does, whether it has one copy or two. The test report will provide you with the genotype for your dog, generally listed as Normal/Normal, Normal/Mutant or Mutant/Mutant. Dogs with even one copy of the mutation should be considered sensitive to listed drugs.
Do I need to tell my vet about my dog’s MDR1 test results?
Yes. If your dog has the mutation, provide a copy of the test results and a copy of the listed drugs to every veterinarian who treats your dog and let them know your dog cannot have those drugs. If you leave your dog in someone’s care, make sure that person has a copy of the test results and drug list in case they have to take the dog to someone other than your regular vet. You might also consider putting a “medic alert” type collar tag on your dog.
What does being an MDR1 carrier mean?
Some testing labs refer to having one copy of MDR1 or other genes as having “carrier” status. This is only accurate if the gene mutation in question is recessive. That is not the case with MDR1, which is incompletely dominant. Dogs with one copy are affected, though to a lesser degree. They will react to every drug on the list if the dosage is high enough.
Can eating feces cause an MDR1 reaction?
If a dogs with the MDR1 mutation eats feces from horses or livestock that have recently been dosed with Ivermectin or related worming products the dog may suffer a reaction. These reactions can be lethal. It isn’t clear how long Ivermectin and related medications will persist after excretion. However, reported reactions were linked to feces from horses and sheep that had been treated within a couple days prior to the incident.
If your dog has even one copy of the MDR1 mutation, keep it away from horses and livestock that have recently been wormed. If you don’t know your dog’s MDR1 status, you should get the dog tested.
If my dog has MDR1 is it safe to get its teeth cleaned?
Yes, provided you make your veterinarian aware of the dogs MDR1 status so the dog will receive anesthesia or tranquilizers that will not cause a reaction.
This is quite a list but if you own or plan to own an aussie... I HIGHLY suggest you print off this list and keep it with you when you get vaccinations or your aussie needs any kind of medication, specifically heartworm and worming medicines. Thousands and millions have died because their owners never knew...
These problem drugs are dispensed in many forms including pills, liquids, injections, and ointments. Check ALL drugs you are considering giving your dog against this list if your dog either carries the mutated gene or has not yet been tested for the gene.
Signs and Symptoms of a reaction:
Hacking cough (similar to kennel cough),
Switching between periods of calmness and
unexplained aggressive behavior to caregivers,
Dilated eyes and trouble focusing
Drugs Suspected to cause
Neurotoxicity (Research is on going):
MS Contin (MSC)
Drugs PROVEN to cause neurotoxicity:
Acepromazine (for tranquilizing, calming, and anesthesic uses)
Butorphanol (Coug Supressants)
Medication Information received from www.busteralert.org .
"Buster was a beautiful red merle Mini Aussie rescue dog who died because he carried the mdr1 genetic mutation. Buster suffered neurotoxicity from a commonly prescribed drug. The 'Buster Alert' is his legacy. It has made us aware that many of our dogs are at risk and that we have to be responsible for learning how to protect them. None of us will ever forget Buster, and many of us will be forever grateful to him. Our perfect dog."
~Marla McCormick, President Mini Aussie Rescue & Support