Discovering Inherited Adult-Onset Deafness in Border Collies
"Leah" ran her first herding trial in the Open Division at age 3. The Border Collie placed third and showed promise. Dave Fetterman, a herding enthusiast, was so impressed he bought her two months later.
One year later, Leah started struggling.
After a year of responding well to whistle directions at distances of up to 600 yards, she would at times no longer heed Fetterman's commands from as close as 150 yards. Fetterman was at a loss to figure out what was happening. Had Leah turned stubborn? Was she practicing selective hearing?
One final clue came on a typical day at Fetterman's Milton, Pa., home. The owner walked downstairs and descended a creaky flight of stairs to let his two dogs out. Along the way he unhooked a noisy metal latch. By the time he reached the kennels, one dog was up and watching.
Leah was still sleeping. The dog was so sound asleep that even after Fetterman opened the chain-link gate to her kennel, Leah was startled when he reached down to touch her.
"Normally, she would have been up when I came down the stairs. She'd have heard me coming and she'd have been alert, because it meant we were going out," Fetterman says. "At first, I wondered if she was just sleeping hard. But as those things add up, you start to realize what's going on."
The reason Leah did not obey commands or wake from her deep slumber was because at age 4 she was beginning to go deaf. Leah's hearing loss was confirmed through a brainstem auditory evoked response (BAER) hearing test conducted at Cornell University.
The test came back as abnormal. "It looked like a 10- or 12-year-old dog's hearing test," recalls Fetterman, who was stunned. "At that point there wasn't any accepted late-onset hearing loss in dogs of any breed."
Now, five years later, Fetterman has helped to increase awareness about the rare condition in Border Collies.
Research conducted at the University of Saskatchewan in Saskatoon, Canada, has helped to increase understanding. Teresa Chu, D.V.M., a graduate student in neuroscience, and Sheila Schmutz, Ph.D., professor of animal and poultry science, presented a poster on their research last year at the fourth biennial international genomics conference held in Saint Malo, France. Chu had a special interest in the hearing study and conducted the research in her spare time.
Their research looked specifically at inherited adult-onset deafness, which is different from congenital deafness, widely reported in other breeds but rare in Border Collies, or geriatric hearing loss, common in dogs 12 and older. Their findings are significant, Schmutz says.
"Veterinarians have been taught primarily that hearing loss is a huge problem in dogs, but it has always been listed as recessive and congenital," she says. "Yet, in humans, there is quite a lot of middle-age hearing loss. And middle-age hearing loss is more often inherited as a dominant condition, meaning you only need a single copy of the mutated gene to have the effect."
The variable nature of how and when deafness progresses is also typical of a dominant disorder, Schmutz says. The discovery of a possible genetic link to adult-onset hearing loss in Border Collies had not been previously reported.
"No one had published research on deafness in Border Collies indicating it could possibly be genetic and not congenital," Chu says. "This is why it was such a shock to the Border Collie community. There are publications on adult-onset deafness in humans related to genetics, but not in dogs."
That may explain why Border Collie owners initially "scoffed" at the idea.
A Look at Genetic Implications Chu had begun conducting BAER hearing tests on various canine breeds susceptible to congenital deafness. One day a breeder-owner brought in a 7-year-old male Border Collie, an agility champion that had been whelped by one of her bitches.
Shortly after the bitch was bred, she became deaf at age 5. The owner waited to breed the male, but feared he, too, may have inherited the trait that caused his dam's hearing loss. Each year the owner brought in the male Border Collie for a BAER hearing test, and each time he tested normal. Then, one year, the dog had an abnormal hearing test.
"When the dog tested abnormal, the owner was devastated," Chu recalls. "She wanted to breed this male because he represented a good line, but she suspected a problem and had him tested year after year. She was trying to be a responsible breeder."
Even so, learning her promising male showed signs of adult-onset deafness was upsetting for the owner — and for Chu.
"It became almost a crusade for me to learn more about the genetic implications of this disease," Chu says.
Though the BAER hearing test helps to detect dogs with adult-onset deafness, no diagnostic test currently enables early identification of those likely to become deaf. Chu conducted a literature review of published research on the subject and came up with nothing about adult-onset deafness in Border Collies, or in any breed. She then posted questions about deafness on Web sites devoted to working stock dogs. A few Border Collie owners provided anecdotal responses about dogs suffering sudden hearing loss.
Chu then discovered "Ally," a Border Collie in the Saskatoon area who went deaf at age 5. "She was a working stock dog who basically could not work anymore because she could not hear," Chu says. "It was heartbreaking for the owners."
Ultimately, Chu adopted Ally.
Then, Chu attended two herding trials, one hosted by Fetterman in Pennsylvania, and the other in Virginia. At the trials Chu conducted BAER hearing tests on 216 Border Collies and collected DNA blood samples.
Owners of 14 of the 216 dogs reported their dogs having some hearing loss. Twelve dogs were found to be bilaterally deaf, or deaf in both ears, and five were unilaterally deaf, or deaf in one ear. A 2-year-old Border Collie showed signs of congenital deafness; five cases appeared to be geriatric deafness; and seven cases were likely adult-onset deafness.
"We learned from testing these dogs and talking to their owners that the dogs typically go deaf gradually between the ages of 3 and 7," says Chu. "It's not likely they go deaf in one day. Owners of stock dogs are very good at picking up deafness in their dogs because they use whistles in training and because dogs work long distances from the owner."
Border Collies that suffered hearing loss were often in the prime of their herding careers and had begun to not respond to distant commands. Learning why dogs no longer respond readily to whistle commands was a relief for some owners.
In one example, Schmutz recalls, "an owner burst into tears and hugged her dog after an abnormal test. 'Now I understand why you won't listen to me when you are far away. I thought you were just being stubborn,' she told the dog."
In their research, Chu and Schmutz found three families of Border Collies showing a pattern of adult-onset deafness. These families do not include the family of Leah, Fetterman's once-promising herder. Fetterman has since learned that out of six dogs in Leah's litter, three went deaf at age 5 or younger. Data from the families Chu and Schmutz studied indicates a possible dominant genetic link.
"I think from the family data and what we know about signs of adult-onset deafness, a dominant pattern of inheritance is logical," Schmutz says. "If the condition were recessive, every time an affected puppy was born it would imply both parents were carriers of the mutated gene as opposed to only one of the parents as in a dominant condition."
Meanwhile, Chu bred Ally, the deaf Border Collie she adopted, with a 7-year-old male Border Collie that had suffered adult-onset deafness. The breeding produced three puppies, all of which were spayed or neutered. Now 4 years old, the pups show no evidence of hearing loss.
"I haven't tested them for awhile, but I can tell you that clinically they hear really well," says Chu, who now practices privately in Saskatoon, Saskatchewan, Canada.
Schmutz plans to conduct a candidate gene study focusing on a few genes shown to cause adult-onset deafness in humans. "We'll first look at this gene in older, normal-hearing Border Collies," she says. "Then we will compare the DNA sequence with that of a deaf Border Collie. If we see a mutation, we'll check for the same mutation in other deaf dogs."
The goal is to identify the mutation and ultimately develop a genetic test to identify carriers and dogs likely to suffer from adult-onset deafness. Potentially, the research may provide a medical model for some forms of inherited hearing loss in humans.
"Right now, there's no way to know if a particular dog is OK to breed until it's too late," Chu says. "A genetic test is needed, because the hearing test is not abnormal until a dog starts to go deaf, which may not be until he is 5 or 7 years old. By then, a dog may have sired or whelped several litters of puppies."
The possibility also exists that adult-onset deafness may be present in other breeds, although none has been detected. One factor that may have made the disorder more notable in Border Collies is that herding dog owners are attuned to changes in a dog's hearing since they work at long distances and since dogs rely so heavily on their hearing ability.
Even so, some owners of Border Collies that go deaf may attribute the hearing loss to something else. Fetterman knows one breeder who blamed his 5-year-old dog's hearing loss on going through dip tanks used to rid sheep of parasites. Another said the noise from flying in an airplane was to blame. Additionally, Border Collies can mask hearing loss for quite awhile because they "tend to pick up on visual cues," Fetterman says. '
As for Leah, she is now 10 and deaf. She no longer competes in herding trials but lives a good life with Fetterman and three Border Collies. Though identification of the genetic mutation causing adult-onset deafness in Border Collies will not directly help Leah, Fetterman hopes the finding will reduce the likelihood of other dogs facing her same fate.