is a serious problem in Australian Cattle Dogs (unilateral +
deafness is around 15%) and appears to be multi allelic and/or
have varying degrees of penetrance with modifiers. That means
you can mate two deaf dogs and get puppies with bilateral hearing.
It is, however, clear that including dogs that are unilaterally
deaf or totally deaf increases the frequency of the disease causing
alleles in the breeding population. Much genetic work needs to
be done in this area.
Like many breeders interested in bettering their chosen breed, I endeavour
to be thoughtful about mating. I aim to improve the breed whilst, concomitantly,
reducing the prevalence of genetically inherited diseases. However, as
many breeders will testify, this can be a delicate balance. In my opinion,
the only certainty is that reliable information is a key to progress.
In this short article I question whether short-cuts in determining disease
states are worth the price of admission.
Congenital hereditary deafness is a problem for over 35 breeds of dog.
Deafness can be unilateral (affecting one ear) or bilateral (affecting
Deafness is the inability to hear and can be caused by either conduction
or neurologic abnormalities. Conduction deafness is caused by abnormalities
of the pinna (external ear), ear canal, tympanic membrane (eardrum),
auditory ossicles or middle ear. Neurologic or sensorineural deafness
is caused by abnormalities of the inner ear, auditory nerve or in the
Recent work suggests
that there could be more than one form of congenital deafness in dogs.
The gene Mitf has been identified as a cause of white
spotting and extreme white spotting in some breeds of dogs including
the Dalmatian and Bull Terrier. In the Stumpy-Tail Cattle Dog, white
spotting is an autosomal recessive trait with incomplete penetrance
that maps to chromosome CFA10.
A BAER test is the
only 100% reliable method for determining that a dog is deaf (or for
measuring the extent of its hearing loss).
stands for "Brainstem Auditory Evoked Response" and
is a procedure using computers to record the electrical activity
to sound stimulation. The waveform represents specific anatomical
points along the auditory neural pathway: the cochlear nerve
and nuclei (waves
I and II), superior olivary nucleus (wave III), lateral lemniscus
(wave IV), and inferior colliculi (wave V).
One simple device that is routinely used for testing puppies
is the BAERCOM™.
My question, and the discussion that I hope to provoke here,
is how accurate and sensitive is this device as compared to the
equipment that resides in a subset of facilities?
The UFI website
BAERCOM includes only the minimum functionality required to test for
hearing ability and eliminates functions that are unnecessary for this
purpose. It does not have the extensive capabilities of the more expensive
audiological testing machines”. Currently it costs US
An unfortunate case of circumstance
Following the untimely death of a cornerstone breeding female
and the disruption of breeders agreement I decided to mate
I had on
my “reserve list”. This female had many meritorious characters,
but she was diagnosed as unilaterally deaf at 8-weeks using the BAERCOM™.
The male I selected has full bilateral hearing according to the BAERCOM™.
The same individual did not test these dogs.
To complicate matters, the female now lived across the continent in Perth
while the identified male two-hours drive away from her. Armed with all
the information and cautionary genetic notes about the possibility of
congenitally deaf puppies, we waited for her to come into season.
Following progesterone testing she was whisked away to meet the future
sire. Introductions were brief and the fertilization was completed without
regard to romance.
Two months later five puppies were born into a welcoming household. The
diligent owners then planned microchipping, vaccinations and BAER testing
with the local veterinarian at 6-weeks of age.
Crisis! The BAERCOM
results suggested that two puppies had normal hearing, two were unilaterally
one was bilaterally
As it was
reported to me, the vet suggested that the two unilaterally
deaf pups should be
retested at 8 weeks. The vet wrote “deaf” on
the paperwork of one female pup. She was not microchipped
The severity of the results caught both the Perth household and me by
surprise. As a non-expert in interpreting BAERCOM results, I sent the
reports to multiple specialists including Professor George Strain (Louisiana
Here is his response in full (reprinted with permission)
First, the device used to test these dogs, called
a BAERCOM, has a long history in my experience of providing
equivocal recordings and misdiagnoses
based on what I contend are poor recordings from
an unreliable a system that is not reliable in the
hands of most users. I see many results sent
to me by doubting owners. The recordings frequently
are full of artifact that can obscure results (visible
to a limited extent on Plain Maverick
and Blackbutt), and it is not possible (last
I knew) to adjust the display gain of the output. The
relative low cost of these units makes them attractive,
but I don’t think you get your money’s
worth with them, and there is no training in
BAER testing to
accompany purchase. Training in human applications
is not adequate.That
said, none of the tracings you sent appear to
show hearing in either ear. However,
to produce a clearer output, I cannot say so
Far from feeling overwhelming dismay when I
read the email I saw a spark of uncertainty
of the results.
that this makes me a “glass half full” person
but my optimism was subsequently validated.
Next, I contacted
Dr’s Susan Sommerlad and Caroline O’Leary
in Queensland as they have been studying
deafness in Australian Stumpy Tail Cattle Dogs.
I made this contact as a geneticist because I know that
a single litter
deaf, unilaterally deaf and normal hearing
puppies can be invaluable in identifying
To resolve the hearing
conundrum, or at least validate the results, I made an appointment
to retest at
Murdoch Vet Hospital
The pups were 8-weeks of age when they
were retested. At Murdoch, Dr Mandy Burrows and
and professional team had
with Dr’s Sommerlad and O’Leary
and we planned to collect blood from all
the dam. Two
I had collected
a cheek swab from the sire of the puppies
so this could be included in the research
Dr Burrows and her team retested each of the puppies and the dam using
the more sensitive and sophisticated Nihon Kohden MEB 9200K, Neuropack
M1 testing unit. Four of the five puppies and the dam were diagnosed
to have normal bilateral hearing. The fifth pup, previously reported
to have normal hearing with BAERCOM testing, was now found to be abnormal
in one ear.
results show 4 of 5 puppies and 1of 1 adult’s
showed conflict between the results.
While it is unlikely that a single
source of error can be identified, the three
factors are age of puppies (6 cf 8
weeks) machine (BAERCOM
cf Nihon Khoden),
(Perth Vet cf Murdoch Vet Hospital).
Costs and Benefits
A puppy’s ear canals don’t open until they are about two
weeks of age and BAER testing may be done on puppies as early as six
weeks. However, some breeders suggest that an 8-week test is more robust.
Sedation is usually not necessary, but some puppies don’t
like being retrained, or having wires
hanging from their face, so it can
be performed while is sedated. Dr
Burrows sedated the puppies prior
One has to assume
that, during its development, the BAERCOM device was
a “gold standard” method of measuring hearing
in dogs. The results of that testing are typically published in the manual
supplied with testing devices. Devices that fare poorly in these initial
tests are typically not released onto the market. So, check your manual
if you own a BAERCOM.
A good manual will
also provide guidelines for interpreting the output of the device – what
response pattern or amplitude of
response would represent intact
deafness. As with any diagnostic
test, there will always be two
risks - falsely
diagnosing deafness and falsely
claiming normal hearing. The manual
explain the likelihood of making
mistakes, when the test is administered
to any breeder.
to see the manual if somebody else
tests your puppies.
even a good test can fail under certain circumstances.
was made accurately – the
machine was properly calibrated, the electrodes were correctly placed,
the tester was adequately trained in administration and interpretation
of results. Some say that the lack of training is a serious issue with
the use of the BAERCOM. As with your own health care, it is always wise
to watch the testing closely, ask questions along the way if you are
not sure things are being done properly, ask for a full explanation of
the results and what was the basis for the tester making his/her decision
of deaf/not deaf. If deafness is identified, don’t
be afraid to get a second opinion
or ask for a retest on a different
a positive or negative test
on two separate occasions is
be true than
a single test.
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