Health Articles

Inherited Canine Deafness - Is it a problem in Bichons?

by Anne Jones RN, BSNE

 
Remember how we never knew we had cataracts in Bichons? Remember how no one was screening for eye diseases? We may be putting ourselves in the same situation when it comes to unilateral and bilateral hearing problems. Inherited deafness is prevalent in white breeds. Most of us realize that it is a major concern in Dalmations. The very factors that make it a concern in other breeds apply to Bichons.

Congenital deafness can be either acquired or inherited. It is the inherited form that we should focus on as breeders. For this article, I have turned to Dr. George Strain, of Louisiana State University, for information. Having met Dr. Strain at the first Parent Club Health Conference, I know him to be an authority and a reputable advisor. I would direct everyone to an article, “Genetics of Deafness in Dogs”, found on the OFA web site at www.offa.org/deaf_genetics.html. Dr. Strain also has a web site at www.lsu.edu/deafness/deaf.htm. His advice should be studied and heeded for those with concern about the genetic issues involved.

Deafness has been determined to be associated with white coated breeds, especially those with piebald and with merle pigmentation patterns. Eighty breeds are listed as potential for the disorder, including Bichons. Bichons tend to have splotches of color in their skin and many will have tan to apricot color on the ears, head and/or body as puppies with the color fading as they approach adult age. To me this appeared to be piebald pigmentation. Coat color fades with age, confusing the issue for me.

When I asked Dr. Strain if Bichons could be considered to be piebald, this is the answer that I received from him:
“I don’t know for certain but it is almost a certainty that Bichons have one of the recessive alleles of the piebald gene – Irish spotting, piebald, or extreme white piebald. This is by far the gene that gives white in dogs partial or solid white. Merle makes alternate light and dark, but Bichons don’t have merle.”

BFCA does have some (limited) data on deafness in Bichons. The numbers are quite low but I go back to the point that we never have routinely screened Bichons and therefore have only word of mouth data. Of concern is that a dog that has unilateral deafness (only one ear affected) will be able to function unless and until the other ear is affected, whether by natural events or by age. By the time he has lost some of his hearing ability due to age or other factors, he has begun to learn the body language that we humans display and by which we “talk” to our dogs all the time. Again quoting Dr. Strain: “It should be noted that a unilaterally deaf dog can be as great a genetic risk for transmission of deafness to its offspring as is a bilaterally deaf dog.”

Again using the incidence of cataracts as an example, Dalmations have the highest incidence of deafness with 8 % of them bilaterally deaf and another 22 % unilaterally deaf. You will recall that we have 8 -10% cataractous Bichons. Do we want to perpetuate a problem in our breeding that is affecting only a percentage of the dogs or do we want to be aware of any genetic malady so that it can be dealt with and bred out of our Bichons? By the way, most Dal breeders will tell you that they routinely euthanize their deaf pups. Is that an outcome that we would want to deal with?

Now that we, as a dedicated group of breeders, have learned that there may be genetically deaf Bichons, we need a way to deal with the problem. In recent years, the BAER screening test has been developed. We now have a method of determining which dogs are deaf, which are unilaterally deaf and which are bilaterally deaf (although a bilaterally deaf pup is pretty easy to spot by the time he is 7-10 weeks old). BAER stands for brainstem auditory evoked response and this test is usually performed at veterinary schools. See www.lsu.edu/deafness/deaf.htm for a description of the BAER test and for a list of test sites. They are quite numerous throughout the country. It has become more common to find clinics at dog shows where many dogs can be screened at a relatively inexpensive cost.

It is important to note that a negative BAER will also rule out acquired deafness, if that is the cause. Deafness can occur as an acquired disease, secondary to intrauterine infections, certain drugs that are toxic to the fetus, other toxicities, and liver disorders. Only by BAER testing can you determine whether an affected pup has deafness but it cannot distinguish between the inherited form or if it is an acquired form. Therefore it is better to test puppies before any acquired form is likely to have an effect (puppies can be tested any time after 5 weeks).

The BFCA health and education committee has asked that the board consider holding a BAER clinic at a national specialty. What is the advantage of screening during specialty week? First is the convenience, second is that it can be cost effective and third is the practicality of determining which of these, our show and breeding Bichons, may be affected. And beyond these factors is the need to have some real numbers to look at to see just what is going on in our breed in regard to this defect. To date no clinic has been scheduled.

In the meantime, the health and education committee strongly urges breeders to take advantage of BAER testing and to report results, good or bad, to the committee. We need to have real numbers to have a better understanding of how the breed is affected by inherited deafness. Having deaf puppies does not doom your breeding program. Since deafness may be bred out of a line with carefully planned breeding programs, knowledge is the key to overcoming the disease.

This article is far from complete in explaining the complexities of inherited deafness. More information will be forthcoming as to inheritance patterns in other breeds and there is much to be learned at the web sites mentioned above. It is our desire to urge testing to better enable BFCA and those involved in research to have statistics that reflect honest data in regard to Bichons. Right now we do not know if we have an issue that needs to be dealt with. Circumstantial evidence indicates we may, given that deafness is more common in white, piebald and merle breeds. Other “bichon” breeds do have the inherited disorder. Now is the time for us to use available testing and then deal with the disorder quickly should it prove to be present in our breed.

This article has been reviewed for accuracy by Dr. George M. Strain, Louisiana State University, Comparative Biomedical Sciences, School of Veterinary Medicine, Baton Rouge LA 70803. Dr. Strain is Professor of Neuroscience at LSU and is a nationally known research scientist. His work has been sponsored by AKC, CHF, The Dalmation Club of America and other dog clubs, as well as by the US Public Health Service (NIH) and private donations. We thank him for his interest in canine deafness.