Congenital sensori-neural deafness

 This is the type of deafness that occurs in puppies and appears to be genetic although the mode of inheritance is not known. This type of deafness can be detected before puppies go to their new homes by BAER testing and be unilateral or bilateral. Note that unilateral deafness is almost impossible to detect without BAER testing in puppies or dogs or any age. The piebald or white factor gene on the S locus has been implicated in deafness in other breeds and is suspected in border collies but has not been extensively studied. The merle gene Mm, (which is dominant) has been implicated in deafness in merle x merle matings (double merle). Pups born from double merle matings are white and frequently deaf (and have other health problems including blindness). 

ABCA article on congenital deafness