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The following is reprinted from the Showboxer-L e-mail list with the permission of Australian breeder, Matthew Cowley, and Dr. George M. Strain.

Introduction by Matthew Cowley:

Some days ago a question was asked as to is there any logical reason to exclude white boxers from the gene pool. It was mooted that perhaps allowing whites would give a selection bonus in providing some more "healthy" dogs for breeding.

I have already replied with some of my thoughts as to why this would not be a good idea but I had one lingering thought that needed investigation. I have done so now to a certain extent by posing some questions to Dr George Strain. For those who don't know of Dr Strain here is some info:

George M. Strain
Professor of Neuroscience
School of Veterinary Medicine
Associate Vice Chancellor for Research & Graduate Studies
Office of Research & Graduate Studies
Louisiana State University

Dr Strain is one of *the* foremost experts in canine deafness in the world. He has given permission for me to post his reply to me on this list, So without further ado...

Dear Dr Strain

I am a boxer breeder from Sydney Australia. As you are aware there is often a lot of controversy surrounding white boxers and deafness. The argument often put forward by those who do not see deafness in white boxers as a problem is that no formal studies have ever been done.

This is something I don't know for sure. My question to you is, have you ever been involved in any formal studies of white boxers and deafness? This would hopefully include information on coloured boxers as well.

I am aware that the cause of deafness in white boxers is due to a pigment deficiency in the ear and the subsequent loss of sensory hair cells, similar I believe to Dalmatians. I am interested in knowing if introducing white boxers into the gene pool as breeding specimens can in turn lead to this deafness increasing in coloured boxers, possibly due to the whites passing on a lot of minus modifiers?

At http://www.lsu.edu/deafness/breeds.htm "Dog Breeds With Reported Congenital Deafness," I note that boxers are prone to congenital deafness. However, the table does not specify white or coloured.

There are suggestions around that white boxers be allowed to breed. The catalyst for this is a larger problem in boxers with Cardiomyopathy. Some people feel that white boxers that may not be affected with BCM should not be excluded from the gene pool simply because they are white and otherwise healthy, the contention being that mating all white boxers to "plain" boxers will produce litters of all "flashy" boxers for the show ring. It is thought by some, not me, that this will increase the gene pool in boxers and help eradicate or control BCM.

One aspect of the "proposal" that I am unclear on is the deafness issue. Is the congenital deafness in boxers limited to whites? If not, could the introduction of whites into the gene pool also introduce the pigment problem in the inner ear to our coloured boxers as well?

An informal poll I ran on a website gave the following figures from amongst a small sampling of boxer owners. Too small to be meaningful probably with only 236 respondents. The question asked was "Have you known a deaf boxer?" The available responses were

Yes - it was white - 43 - 18.22%
Yes - it was coloured - 5 - 2.12%
No - 188 - 79.66%.

I do realize that there are other causes of deafness and I also realize that without BAER testing these figures probably only reflect bilaterally deaf boxers. But I was interested that there were 5 responses to coloured deaf boxers. Unfortunately I do not know the colour of the parent boxers but am in the process of trying to get this information now.

If you have any information you can share with me on this subject I would be greatly appreciative.

Thank you for your time.

Matthew Cowley R.N.
Marimat Boxers - Australia
http://www.marimat.com/

Dear Matthew,

I am unaware of studies specific to the boxer and white boxers. I suspect it is very similar to the circumstances of the Norwegian dunkerhound, where something like 75% of the whites are deaf [Foss, I. (1981). Development of hearing and vision, and morphological examination of the inner ear in hereditarily deaf white Norwegian dunkerhounds and normal dogs (black and dappled Norwegian dunkerhounds). Masters thesis, Cornell University, Ithaca, NY. 133 pp]. When deafness is first addressed within a breed, individuals will often claim that (1) this is not a real problem in our breed, or (2) no studies have been done so it is not a problem, or (3) what are you trying to do - destroy the reputation of our breed? This problem is similar among all of the breeds that carry one of the alleles of the piebald gene (extreme-white piebald, piebald, and Irish spotting). This gene is recessive, so dogs with white are homozygous. White results from the gene suppressing melanocytes (pigment cells). I have become convinced from working on this for more than a decade that a second gene regulates how strongly the piebald gene affects a dog, since the problem does not appear to conform to simple recessive inheritance. In Dals, weak piebald expression results in a patch, where the white fails to cover up the underlying black or liver color (these dogs are less likely to be deaf). Strong piebald expression leads to suppression of melanocytes in the iris (=> blue eyes, more likely to be deaf) and in the blood supply of the cochlea (=> deafness). One deaf ear is still genetic deafness and these dogs produce increased numbers of deaf offspring. Clearly from the data you compiled (the first I’ve seen) deafness in boxers does not require that the dog be white, but if it IS white the chances are much higher. In English cocker spaniels deafness is absent in solid colored dogs (I've only seen one case, and it may have carried one copy of the recessive piebald gene) but present in parti-colors. In bull terriers, deafness is 10X more prevalent in whites than in colored (which still have white). Note also that if one is not looking for deafness one often does not find it -- typically for each identified dog that is deaf in both ears there will be 2-3 dogs deaf in just one ear, and these dogs are not at all obvious from behavior, so they get bred. These uni’s at a young age show difficulty localizing the source of a sound, but they soon adapt.

It is my opinion that white boxers carry a version of the regulatory gene that causes over- expression of the piebald gene, producing heavy white color, blue eyes, and deafness. Breeding these dogs back into the boxer gene pool will very likely increase the overall incidence of deafness in ALL boxers (white or otherwise). I do not know the genetics of BCM, but it is not likely that white boxers are free of the defect, and nothing associated with pigmentation (or its absence) should logically protect against BCM. Breeding a white boxer without BCM back into the breed gene pool is not likely to affect BCM incidence, and in fact could worsen it if BCM is polygenic and the white boxer carries some of the responsible genes. If asked, I would be opposed to breeding white boxers -- to either whites or colors. If this practice is continued the prevalence of deafness in all boxers will increase as has happened with other breeds. I know that there is a strong group of advocates for white boxers, mostly because there is always attraction to something novel. To me it seems totally without logic to continue a breeding practice which, based on all available knowledge, will increase the prevalence of hereditary disease in a dog breed.

I hope this is of some help. I would appreciate being kept up to date on any data you accumulate.

George M. Strain
Associate Vice Chancellor
Office of Research & Graduate Studies
Louisiana State University
240 Thomas Boyd Hall
Baton Rouge, LA 70803
Voice 225-578-5833 Fax 225-578-5983
ORGS Web: www.research.lsu.edu
Personal Research Web: www.lsu.edu/deafness/deaf.htm