About congenital deafness in Yakutian Laikas and other breeds with extreme white spotting.
Almost all Yakutian Laika breeders have a certain understanding of congenital deafness and know that it is somehow related to pigmentation. When I started working with the breed, I imagined a semi-deaf Yakut Laika as a white (or at least white-headed) dog with poorly colored nose, eyelids, and lips. But one day I saw a photo of a puppy that shocked me. I am showing it to you too, it's the puppy in "photo 1". Rich color on the body with excellent pigmentation, a wide symmetrical mask on the head, and both tested parents with BAER +/+. This raised a lot of questions. How is this possible? Can the BAER test be wrong in this case? What percentage of semi-deaf puppies do we get in our litters?
Fate once introduced me to veterinarian Tatyana Prokhorova She is one of the first in our city to use BAER as a Dalmatian breeder. She has accumulated over ten years of practical testing experience, supplemented with veterinary knowledge. We have decided to answer these questions together.
☝🏻About the terms: BAER is both a testing method and the obtained result (literally Brainstem Auditory Evoked Response). BAER +/+ is the result of a healthy puppy, both ears can hear. BAER +/- is the result of a semi-deaf (unilateral) puppy. BAER -/- is a fully deaf (bilateral) dog. Sensorineural deafness is congenital deafness.
❓Is there really a connection with pigmentation? The biological mechanism of congenital deafness.
"It is believed that congenital deafness occurs in dogs with the extreme white spotting gene: Dalmatians, white Bull Terriers and Boxers, English Setters, Yakutian Laikas, and the merle coloration: Collies, Corgis, Dachshunds, Bobtails," Tatiana explains. "It is associated with an anomaly in the migration of pigment cells or their interaction with other structures in the inner ear. This leads to the degeneration of nerve endings in the first weeks of a puppy's life."
This defect has a genetic nature, and several genes are responsible for the "breakdown". Therefore, we talk about the polygenic inheritance of the disease. However, these genes have not been found yet.
"There is also a suggestion that blue-eyed dogs with a lack of pigment in the iris are accompanied by a lack of pigment in the inner ear. But accumulated practice shows that deafness is equally detected in blue-eyed and brown-eyed dogs» And if we talk about Yakutian Laikas, it is evident that even brightly colored representatives of the breed can be semi-deaf.
❓Could it be a mistake?! About the accuracy of the BAER test.
The BAER test is currently the only instrumental way to confirm or exclude unilateral and bilateral deafness. This electrodiagnostic method was invented in the 1960s, and its effectiveness has been fully verified.
There is no need to delve into the essence of the research. It is enough to know that its result is a graph created separately for each ear. The graph of a hearing ear will show 4-6 characteristic peaks, while the graph of a deaf ear will be flat (see the last illustration).
There are disputed cases where a graph with low peaks and excessive delays can be obtained. Usually, this is related to residual hearing in young puppies. In disputed cases, a series of tests can be conducted on the same day or at different ages.
"Again, using the example of the Dalmatian breed - our breeders strive to test 100% standard and faulty puppies using BAER testing for 10 years - I don't know of any cases of false positive or false negative test results," Tatiana shares her experience.
❓What is the optimal age and the rules for conducting the test?
The BAER test can be conducted at any age. Puppies are usually tested from 5-6 weeks old. Some veterinary clinics claim that BAER tests done without sedation are not reliable. But that is not true.
"On one hand, muscle movements and contractions can influence the graph, creating false positive or false negative results. However, conducting the test under sedation is desirable when dealing with very active patients who do not allow the test to be carried out. We test puppies and adult Dalmatians without sedation. Several times, the tests were conducted under anesthesia, specifically in disputed cases, and the results were consistent."
❓BAER shows a -/- result. Is it a final diagnosis? The definitiveness of the diagnosis and inheritance.
In the case of testing an adult dog, it may reveal a conductive hearing loss. The cause may be various problems or conditions: foreign body in the ear canal, thickening or perforation of the eardrum, ossicular sclerosis, or fluid in the middle ear.
On BAER, this manifests as reduced amplitudes and prolonged peak latency (if the problem is severe, the graph may be flat). Fortunately, many cases of such hearing loss can be treated, but sensorineural deafness, which we are talking about, is incurable.
❓ Why is it important for breeders to test their puppies? After all, even tested parents +/+ can produce a puppy +/- or even -/-
Yes, that is true because there are no genetic tests that can exclude carriers. A dog +/+ can be a carrier or can be clear. A dog +/- is 100% a carrier. If we mate one of the dogs with a +/- test, we increase the risk of getting bilateral puppies in the litter by 25%. Mating two dogs +/- increases the risk by 50%
BAER testing is a simple, fast, and reliable way to minimize the risk of breeding deaf puppies. It is the breeder's responsibility zone.
❓About unilateral dogs and their prevalence in the breed.
- My dog can hear when a cookie falls on the kitchen floor from the hallway, does that mean her hearing is perfect?
Unfortunately, no. However, such dogs fully compensate (by human standards) for the hearing loss on one side and give the impression of being completely healthy dogs. Partial deafness does not affect their role as full-fledged family members and excellent companions. The only way to identify +/- is through testing.
It should be noted that there is currently limited information available on Yakutian Laikas. It cannot be confidently stated that +/- dogs make up a very low percentage in the breed. Not all breeders test their litters.
During my time in the breed, I have seen one breeder start publishing the results of testing their litters but quickly stopped doing so. When no one else is testing their puppies (or not publishing the data), and one breeder occasionally detects +/-, it creates a false impression that they have some sick dogs. However, it is just a general problem in the breed. The more breeders understand this, the better the overall results of their work will be.
Photos of all dogs were taken from open sources or kindly provided by their owners and have BAER +/-
Veterinarian Tatyana Prokhorova and CoolJack kennel.