BAER - hearing test
Deaf Havanese have been appearing sporadically for years but, thinking it was an isolated incident, breeders rarely shared the information. This heritable disorder may be pigment related. There is some suggestion that affected Havanese (unilateral or bilateral) are particoloured of some kind, (parti, piebald, extreme) or all white. Almost all solid colour Havanese tested are normal in both ears, barring external ear issues such as wax buildup. It is possible, though unproven, that dogs carrying or displaying broken colour/pattern genes are vulnerable, and not all of them have inherited the mutation which causes the problem so this does NOT mean that all parti/ white Havanese are deaf, just that all the affected dogs to date seem to be parti or white. This phenomenon has been noted in other breeds with predominantly white coats such as the Damatian and Bulldog. Interestingly, many Havanese hearing clinics have had zero incidence of deafness. Ocasionally there have been one or two dogs with inconclusive or failed tests attributed to external issues such as excess hair in the ears or an accumulation of earwax. After cleaning the ears, subsequent hearing tests have been normal. Higher incidence has appeared in regional pockets, leading to the belief that such heritable deafness may run in breedlines.
You cannot check hearing yourself. Most people with unilaterally affected Havanese are completely unaware that a problem exists. Hearing status can be positively ascertained by a Brainstem Auditory Evoked Response test (BAER) which detects electrical activity in the ear and auditory pathways in the brain. It is a very simple test and can be done anytime after a puppy is about 6 weeks old. It is a one time test. The ears should be clean and free of infection, wax build-up and hair overgrowth as these may affect test results. The test takes approximately 10-15 minutes to complete. Each ear is tested individually. Small ear phones deliver the stimulus and response data is collected through tiny electrodes with the results being displayed on a computer screen. A normal response waveform shows a series of peaks and valleys while the response from a deaf ear is essentially a flat line. Dogs show no evidence of discomfort from the electrodes though they may object slightly to the gentle restraint. Sedation is unnecessary; even young puppies take the test in stride. At the end of the procedure, the recorded waveform is printed out.
BAER testing can be difficult to locate though is available at veterinary colleges. A test for a single dog may be expensive but prices are substantially lower if done with multiple dogs or at a hearing clinic. Some Veterinary colleges have recently acquired portable equipment which may make BAER clinics more easily accessible in upcoming years. At this time, among those affected, there appears to be many more unilaterally than bilaterally affected Havanese, but incidence may rise as untested unilaterals are bred together. Caution should be exercised when considering breeding known unilateral deaf dogs as the likelihood of deafness may be significantly increased in litters with unilaterally deaf parent(s). Until a definitive test for this gene mutation is developed, BAER testing breeding stock and puppies prior to placement is one way to help minimize the incidence of deafness in our breed.