DNA Tests For Dogs

When Petunia, a 13-year-old pug, started having trouble walking, her concerned owners bought a $65 genetic test. It turned up positive for a mutation linked to a degenerative disease similar to ALS in humans.

To keep her from suffering, they put her to sleep.

The trouble with Petunia's story, notes a commentary in the prestigious science journal Nature, is that research suggests only a small percentage of dogs who test positive for the mutation will actually develop the disease.

"That is a real case," said Dr. Lisa Moses, a veterinarian at the MSPCA-Angell Animal Medical Center in Boston and a research scholar on bioethics at Harvard. "And it is one, but there have been many of them. In fact, a number of cases just like that one are what started me thinking about this years ago, when the first genetic tests started to be used routinely."

DNA testing of dogs is a booming business. Over the last decade or so, the genes of hundreds of thousands of dogs have been analyzed, whether to determine which breeds the dogs belong to, or, as with Petunia, to check for genetic diseases. But Moses and two other Boston-based experts warn in Nature that the pet genetics industry is running too wild, and they're calling for it to be reined in.

"People are trying to make decisions to spare what they see as future suffering — which I totally understand and support," Moses said. "I just want to make sure that we're making those decisions for really good reasons."

But it can be hard to be sure, because pet genetic testing is virtually unregulated.

"One of the alternative titles we had proposed to Nature was 'Pet Genomic Medicine: Owners Beware,' " said veterinarian Steven Niemi, who co-authored the Nature commentary and is the director of the Office of Animal Resources at Harvard. "One of the purposes of this article was just a heads-up to everybody that this needs some serious attention in an organized fashion."

The article calls for several remedies, including quality standards for how pet genetic tests are performed and how results are shared, as well as counselors who could help owners interpret results. It points out that much of the testing is for genes whose power to cause disease hasn't been fully nailed down.

Co-author Elinor Karlsson, a leading researcher on dog genetics based at the UMass Medical School and the Broad Institute, said she was "aghast" when she learned from Moses that genetic research like hers is being used to make clinical decisions — including euthanasia.

"It really upset me," she said. "Both the idea that people were already using genetics like this and the idea that the papers that I've published on things like bone cancer and compulsive disorder may also end up being used as tests, and that people wouldn't understand what the limitations were of the work that we've done so far."

In particular, she said, often a first step in research is to find a mutation that's more common in dogs that do have a disease than dogs that don't. But there's a critical second step, which is to look at a new group of dogs and see how well that mutation predicts whether they'll get sick.

"It's not that there's anything wrong with the science that has been done," Karlsson said. "But often they've done it only in a very small group of dogs, or only in one breed, and they've usually never done this kind of next study, of actually looking at whether it's useful for predicting disease."

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