Origin of hereditary deafness
List of dogs tested for deafness (Only unhurt subjects appear) – Direct tests recorded by the CCS and the SBTCF stopped on 05 March 2016.
Deafness in dogs, whose bottom of the dress is white, knows a significant percentage of hereditary deafness by insufficiency of pigment in certain cells of the cochlea (inner ear) which causes their degeneration at the age of 3 to 4 weeks.
This is to relate to the excessive selection of the white mantle. The white coat is determined by the gene SW s, s as spotting, was white, (MITF gene located on the chromosome N20), named “extreme white piebald”, in French gene of the “invasive variegation”; the adjective “invasive” is quite telling because this gene comes out, if we can say the role that was expected of him: it is not limited to determine the coat but extends its action in the inner ear … This gene is common to White Bull Terrier and Dalmatian among others.
Since 1991, the work of Dr. Strain of the University of Baton Rouge shows, by the joint statistical study of pedigrees and results of PEA on large numbers of dalmatians that deafness is directly related to the ability of the gene SW to s expressing in terms of the influence, facilitator or inhibitor, that would probably have on him several other genes (polygenes).
Recognize deafness on the farm
Bilateral deafness
A deaf bilateral dog (SB) is a dog imposing a very restrictive lifestyle.
An SB puppy can and should be recognized at breeding.
Unilateral hearing
An EU dog (Unilateral Hearing) is considered an average observer, unnoticed because the dog leads a completely normal life, a very slight delay in locating certain noises that can sometimes be noted.
Recognize bilateral deafness
The jerk reaction (at the end of the 4th week)
The puppy to be tested must be in a natural position, lying face down on a soft and warm surface.
The person who tests puts his hands 5 to 10 cm above the puppy’s head and snaps them: a normal puppy lifts on his forelegs and then falls back.
A SB puppy exhibits a specific behavior: very deep and slow sleep, a certain isolation from other puppies (puppy “too calm”), reduced play sequences, reduced ear mobility, the possibility of aggression with regard to his brothers and sisters whose complaints he does not perceive during the games.
Recognize unilateral hearing: hearing puppies with one ear
It is extremely difficult, if not impossible, to recognize an EU puppy, at least on the farm.
It is, therefore, necessary to resort to a reliable test that does not involve the active participation of the puppy: the registration of PEA (Auditive Evoked Potentials) meets this requirement.
The test is practiced from the age of 6 weeks, not before. It is the computer-based recording of the electrical activity of the cochlea, the portion of the inner ear affected by deafness.
It is practiced under general anesthesia; 3 subcutaneous electrodes are placed on the skull and at the base of the ear canals. Sound “clicks” are emitted by earphones placed in the ears. The electrical activity received and recorded in the form of curves makes it possible to evaluate the auditory function.