May 20, 2010
The Purebred Paradox
Is the quest for the "perfect" dog driving a genetic health crisis?
by Carrie Allan
In the days leading up to the annual Westminster Kennel Club Dog Show, the hotels around Madison Square Garden in New York City fill up with owners, handlers, and hundreds of purebred dogs. They come from around the country, spiffed up and ready to shine: prancing white poodles with their fur teased into towering pompadours, basset hounds with their ears held up in shower caps to keep them from dragging on the ground, bright-eyed Chihuahuas peering eagerly out of fancy carriers.
For these show dogs, who must be registered with the American Kennel Club, this is the Oscars—“the symbol of the purebred dog, in show rings as well as in millions of television homes across America,” according to its marketers. They vie for a hierarchy of awards: best of breed, best in group (sporting, herding, hound, toy), and, most prestigious of all, best in show.
In an interview filmed during the show this February, Kimberley Meredith-Cavanna explained the criteria that she and other judges consider when determining how closely these premium pooches match the “ideal specimen” prescribed by each breed’s parent club. “We’re looking to see what its head should look like, its eye set, its proportions, its size, how the dog moves, and how it should be built,” she said.
While it may seem as though contestants are competing against each other, they are actually judged against standards written by the clubs and ratified by the AKC: Are this dog’s ears long enough to make her an ideal beagle? Is that one’s head big enough to make him a prime example of English bulldog-ness? Does this Rhodesian ridgeback have the correct symmetrical ridge of hair along her spine?
Watching the lively animals in the ring, how can a dog lover not be charmed? Westminster and other shows like the annual AKC/Eukanuba Championship have a loyal following among breeders and casual dog lovers alike.
But the shows are not without their critics. Though the dogs who compete at Westminster are beautiful and most are likely healthy, the rise of such spectacles—and judging measures that in some cases emphasize appearance over welfare—has been blamed for a host of genetic health problems facing scores of breeds today.
An MRI revealed the painful truth about the Cavalier King Charles spaniel Pfeiffer had bought at a pet store: At less than a year old, Daisy had syringomyelia, a condition in which fluid-filled cavities occur within the spinal cord near the brain.
Brachycephalic (or short-faced) breeds like bulldogs and pugs suffer from breathing problems; Great Danes and other large dogs from joint problems; long dogs like dachshunds and basset hounds from back problems; wrinkly-faced dogs like boxers and shar-peis from skin and eye problems. And due to prolific production to meet public demand, the most coveted dogs tend to have the most genetic disorders; Labrador retrievers, who’ve topped the AKC’s popularity list for 19 years, are prone to around 50 inherited conditions.
The stories of those who fall in love with these animals, only to watch them suffer, are often heartbreaking. On New Year’s Eve, Janice Pfeiffer’s dog Daisy suddenly “started yelping really loud,” says the New Hampshire resident. “It turned out she had a seizure, and she recovered from the seizure on the floor, and crawled into a corner and just looked glassy-eyed.”
An MRI revealed the painful truth about the Cavalier King Charles spaniel Pfeiffer had bought at a pet store: At less than a year old, Daisy had syringomyelia, a condition in which fluid-filled cavities occur within the spinal cord near the brain. In severe cases, a dog’s brain swells beyond the space provided by her skull. Some studies have indicated that, due to its prevalence in the breed’s gene pool, 30 to 70 percent of Cavaliers will develop the condition.
The Genetic History of Man’s Best Friend
Once upon a time, people believed that purebred dogs were naturally healthier than mixed breeds. How have we arrived at a point where it may be safer to presume the opposite?
Like humans, dogs are diverse in appearance—perhaps one of the reasons we love and identify with them. But that wasn’t always the case.
All dogs share ancestry with the wolf, but since their domestication at least 15,000 years ago, they’ve been selectively bred by people to assist with herding, hunting, and—in the case of the Pekingese—warming the laps of Chinese emperors. For the better part of canine history, the physiques of breeds were driven by dogs’ role as working animals, a classic example of the dictum that form follows function.
As that role diminished and pet keeping became common, dogs began to be bred more for appearance. You can see the resulting diversity any time you go to the dog park and watch an amorous Chihuahua trying to make time with an embarrassed St. Bernard, while a baffled Afghan and whippet look on. They’re all dogs—but if you didn’t know that, you might believe they were different species.
The thought wouldn’t be unreasonable. A recent study in The American Naturalist compared the diversity in the dog to that across the entire order carnivora. They found more difference between the skulls of a Pekingese and a collie than between those of a walrus and a coati, a South American member of the raccoon family.
Left to their own devices, dogs will be dogs—and will eventually intermingle enough to level out extreme differences within the species. Natural selection ensues and hybrid vigor results: Witness the similar color and size of mutts in Mexico and other countries where they’re allowed to roam. To protect particular characteristics, though, breed enthusiasts have long guarded a highly controlled process, regulating genetic lines and creating registries that stipulate which animals can be bred to produce more of the same type.
But therein lies the problem: The more limited the number of mates, the greater the chance a dog will be bred with a relative who shares similar genes. Genetic diseases are caused by recessive genes, so a good gene from one parent will trump a bad gene from the other. But if both parents have a bad gene—such as one that predisposes them to hip dysplasia or blindness—the likelihood of a sick puppy increases.
“What happens when you have a small and inbreeding population is that the probability of two negative recessive genes finding each other increases as the gene pool chokes down to a smaller and smaller pool,” says Patrick Burns, a Dogs Today columnist who frequently writes about genetic health issues on his blog, Terrierman’s Daily Dose.
A closed registry that allows no “new blood” into the mix exacerbates the problem, he argues: “In many AKC dogs, the founding gene pool was less than 50 dogs. For some breeds, it was less than 20 dogs.”