Multi-drug resistance (MDR1) testing for dogs

Multi-drug resistance (MDR1) is also sometimes known as multi-drug sensitivity, and it leads to a hypersensitivity in some dog to a fairly broad range of different drugs including common antibiotics and painkillers. Dogs that have the condition develop a defect in the bodily systems that are responsible for moving certain drugs out of the brain, which can lead to a dangerous accumulation of toxins in the brain itself, causing a range of serious symptoms including seizures, and that can ultimately prove fatal.

The condition is a hereditary one, passed on through the breed lines of affected dogs, and cannot be caught or developed in other ways. Because the condition affects a significant number of dogs of certain breeds, pre-breeding testing for at-risk dogs is strongly recommended, so that would-be breeders can make an informed decision about the risk factors when making the decision about which dogs to breed.

In this article, we will look at multi-drug resistance (MDR1) in dogs in more detail, including what sort of dogs are affected by it, how the heredity of the condition works, and how to get your dog tested. Read on to learn more.

More about multi-drug resistance in dogs

Multi-drug resistance most commonly presents in various different types of herding dog breeds, and can cause hypersensitivity to a wide range of different drugs and medications such as painkillers, antibiotics, sedatives and medications used for chemotherapy.

If any of the drugs that the dog in question is sensitive to are prescribed to the an affected dog, the brain’s ability to naturally remove and process out these drugs fails, leading them to build up in the brain to dangerously toxic levels, which in turn leads to severe symptoms such as seizures, nerve disorders and blindness, and the toxicity at the root of it can ultimately prove fatal.

What sort of dogs can be affected by the condition?

Multi-drug resistance tends to affect various different dog breeds from the herding-working group, including the Border collie, Old English sheepdog, rough collie, smooth collie, and German shepherd. If your dog is of any other breed, you can find out if they are at risk for the condition (and any other hereditary health conditions that affect the breed too) by using The Kennel Club’s DNA Screening Schemes by Breed search tool.

Additionally, it is worth bearing in mind the fact that cross-breeds and mongrels that have ancestry from one of the at-risk breeds may inherit and pass the condition on as well, but data for non-pedigree dogs is not held by The Kennel Club.

Only dogs that have inherited the condition can be affected by it-the condition cannot be caught or passed on from dog to dog other than through the genes.

Dogs that have the condition will only be affected by it if they are given one of the drugs known to lead to problems-and so knowing whether or not your dog has the condition is important, because yourself and your vet will then be able to make an informed decision about the best medications to prescribe for your dog in various different situations, without running the risk of causing them harm.

How does the heredity of the condition work?

Multi-drug resistance is an autosomal recessive condition, which means that for a dog to be affected by the condition themselves, they have to inherit the right combination of faulty genes from their parent dogs.

If both of the parent dogs are affected by the condition, they will pass it on to their offspring. If one affected dog and one normal dog breed, their offspring will become carriers of the faulty gene in 50% of cases.

If neither parent dog is affected by or a carrier of the condition, their litter will be free of the condition too.

How to get your dog tested

If you own one of the breeds of dog that are at risk for the condition, pre-breeding testing is particularly important in order to ensure that only healthy dogs are bred, and so do not pass the condition on to their offspring.

Even if you do not intend to breed from your dog, it is a good idea to either have them tested or ask the dog’s breeder for testing results for the breed line if they belong to an affected breed, so that you and your vet will know what sort of medications are safe to use for them.

In order to have your dog tested for multi-drug resistance, you will need to ask your vet to take a buccal sample from the inside of the dog’s cheek, which is then sent away to an approved laboratory for testing.

The results are then returned to the dog’s owner, and a copy is also submitted to The Kennel Club for inclusion in their breed health information statistics. To find a laboratory that can test your dog’s sample for you, check out this information section on The Kennel Club’s website.