New England Old English Sheepdog Rescue, Inc.
 
Old English Sheepdogs and Multidrug Sensitivity

You may have heard that some Old English Sheepdogs are sensitive (meaning they can have a bad, and in relatively rare cases, fatal reactions) to e.g. ivermectin, one of the main ingredients in a popular heartworm preventative, though generally even susceptible dogs can tolerate the levels administered for heartworm prevention. The breed most closely associated with this phenomenon is the Collie, though there have been instances of similar reactions in several other herding breeds, especially, but also some sight hounds and even mixed breeds. Researchers at Washington State University discovered that what the dogs that experienced these reactions have in common is a mutation in the multi-drug resistance gene (MDR1). They then developed a test that can screen for this gene mutation. You can read more about it at http://www.vetmed.wsu.edu/depts-VCPL/

The test is very simple. It’s a simple cheek swab and the test kit can be ordered online at: http://www.vetmed.wsu.edu/depts-VCPL/test.aspx You do not need a trip to the vet to do this. I tested one of my own dogs after she had a bad reaction to ketamine and it was remarkably simple to collect the DNA needed and mail the sample in. From this, the researchers can ascertain a dog’s genetic make-up vis-à-vis this gene. The dog’s results will come back as one of the following:

normal/normal - the dog does not have the mutation so would not be expected to be sensitive to the drugs in question.

mutant/normal - the dog inherited one copy of the mutated genes from one of his parents and would be expected to have some sensitivities.

mutant/mutant – both of the parents of this dog have to be carriers of the mutant gene and both passed them on to the offspring – these dogs are at especially high risk of potentially fatal reactions to certain drugs.

In addition to ivermectin, there are a number of other drugs that have been documented to cause adverse effects in dogs who carry the MRD1 gene mutation, including loperamide (Imodium TM ) and acepromazine. For a complete list, please see: http://www.vetmed.wsu.edu/depts-VCPL/drugs.aspx (the testing and problem drug information pages can also be reached by following links from the first link provided above).

What does this mean for you and your Sheepdog?

Well, the researchers don’t quite know yet. When they first started testing, they found one affected Old English. That was enough to get our breed included on the list of possibles, but not enough to make anyone terribly concerned about the issue. More recently, a researcher at Washington State University happened to contact a veterinarian in Wisconsin who submitted an OES DNA sample and shared that in the last few months they had seen a sudden spike in OES testing positive for MDR1 and that they were concerned. Dr Spaeth had submitted a DNA sample on, as it happens, a rescue dog NEOESR was handling in terms of medical bills and so on, and who ended up in Wisconsin. The rescue dog, Sadie, was originally from Indiana and was being treated for mange. Three other OES had been dumped at a shelter in Indiana at roughly the same time. Their backgrounds were completely unknown, but coincidentally they also had mange and, when treated, one of them died. Mange is typically treated with high doses of ivermectin. This made your very own Grannie Annie suspicious (and concerned), which led to Sadie’s foster mom (she has since failed Foster 101, but we’re not supposed to talk about that) to have Sadie tested for the MDR1 gene. She came back mutant/normal.

Is there a moral to this story? We’re not sure yet. My own dog whom I had tested came back normal/normal, so it is possible to have drug reactions in the absence of MDR1. I don’t think anyone is suggesting everyone rush out and get their dogs tested immediately, but if you’re concerned, or your vet is concerned, and especially if your dog needs to be treated with any of the drugs listed (one of them is a chemotherapy drug, heaven forbid), it might be worth your while to consider testing.

Certainly I think those of us involved in rescue need to be vigilant. There is as of yet no clear sign how widespread the gene mutation might be, but rescue dogs are often especially vulnerable if there is an issue, because we don’t usually know their background all that well, and some of them, like Sadie, come in needing some serious medical attention.

(Amy Spaeth DVM may be reached at
jacksonpethospital@charterinternet.net)

Respectfully submitted,
Kristine Loland
Part of Wisconsin OES Rescue