I graduated from the Washington State University College of Veterinary Medicine. This most likely makes me somewhat biased about the Veterinary Clinical Pharmacology Laboratory at Washington State University in Pullman, Washington.
But this lab has made great strides in research that has saved many dogs in the herding breed group — such as Australian Shepherds — from fatal drug reactions.
Some dogs, particularly herding breeds, have a mutation in the MDR1 gene, leaving them with a multidrug sensitivity, a genetic predisposition to have adverse reactions caused by commonly used drugs.
This mutation can cause loss of balance, depression, disorientation, excess salivation, pupil dilation, abnormal movement of the eyes, blindness, tremors, inability to get up, coma, respiratory problems, and even death when they are given a commonly used drug from the “problem drug” list.
Thankfully, WSU’s Veterinary Clinical Pharmacology Laboratory has discovered the cause and invented a method (MDR1 test) to determine if a dog has this condition.
Approximately three of every four Collies in the United States have the mutant MDR1 gene. The frequency is about the same in Australia and France so it is likely that most Collies worldwide have the mutation.
The MDR1 mutation has also been found in Australian Shepherds, Shetland Sheepdogs (Shelties), Old English Sheepdogs, English Shepherds, German Shepherds, Longhaired Whippets, Silken Windhounds and a variety of mixed breed dogs.
The only way to know if an individual dog has the mutant MDR1 gene is to have the animal tested. As more dogs are tested, more breeds will probably be added to the list of affected breeds.
Breeds known to be affected by the MDR1 mutation include the following:
» Collie, 70%
» Longhaired Whippet, 65%
» Australian Shepherd, 50%
» Australian Shepherd, Mini, 50%
» McNab, 30%
» Silken Windhound, 30%
» English Shepherd, 15%
» Shetland Sheepdog, 15%
» German Shepherd, 10%
» Herding Breed Cross, 10%
» Mixed Breed, 5%
» Old English Sheepdog, 5%
» Border Collie, < 5%
WSU has identified many mixed-breed dogs with the MDR1 mutation. Some of them have no resemblance to herding breed dogs. It is true that the MDR1 mutation has been identified only in herding breed dogs, so if your dog tests positive for the MDR1 mutation, it is highly likely that your dog has an ancestor that is one of the herding breeds.
A puppy can be tested as soon as it is weaned from its mother. That is why they strongly recommend testing mixed-breed dogs for the MDR1 mutation prior to administering any of the problem drugs that are listed on the lab website
The MDR1 genotype test will determine if your dog has the MDR1 mutation.
The testing process is simple and no special training is required to collect the sample, which is obtained by brushing cells from the inside of the cheek with a cheek swab/brush. You will receive swab/brushes and sample collection instructions in the test kit, and an instructional video can be found on the lab website.
Test results are usually received within one to two weeks.
Click here for more information from the WSU Veterinary Clinical Pharmacology Laboratory, or contact the lab at vcpl@vetmed.wsu.edu or 509.335.3745 to receive a testing kit. The cost of the kit is $60.
Drugs that cause life-threatening problems in dogs with the MDR1 mutation include some with the combinations of flea and heartworm preventive products (those containing spinosad), as well as other anti-parasitic drugs, some anti-diarrhea drugs, some tranquilizers, some chemotherapy drugs and some analgesic drugs.
If you have a herding breed or a possible cross of a herding breed, completing this simple test can potentially save your dog’s life. Please advise your veterinarian if your dog has been tested and if it has an MDR1 gene mutation so they can avoid problem drugs that could harm your dog.
The laboratory at WSU is very helpful by phone and email. Go Cougs!
— Dr. Bonnie Franklin is a relief veterinarian who grew up in Santa Barbara. She earned her doctorate of veterinary medicine from a joint program of Washington State and Oregon State universities, a master’s degree in wildlife biology from Cal Poly, San Luis Obispo, and does consulting work with the U.S. Forest Service. Click here for previous columns. The opinions expressed are her own.